Patent Application
20090086877
This invention relates to energy conversion using host materials comprising molecular deuterium (D2) and/or hydrogen-deuterium (HD) through newly discovered reactions that couple energy directly to high frequency vibrational modes of a solid.
U.S. patent application Ser. No. 10/440,426 filed May 19, 2003 describes a framework for understanding nuclear reactions occurring in various host materials as well as embodiments for converting energy generated by such nuclear reactions into useful energy. The present application describes further embodiments for the conversion of energy from nuclear reactions in materials comprising molecular deuterium (D2) and/or hydrogen-deuterium (HD) into useful energy.
According to one aspect, a method, comprises stimulating a material to cause reactions in the material, wherein the material comprises at least one of molecular deuterium (D2) and molecular hydrogen-deuterium (HD), and removing energy generated by the reactions from the material.
An apparatus comprises a material comprising at least one of molecular deuterium (D2) and molecular hydrogen-deuterium (HD); an excitation source comprising a device selected from the group consisting of an electromagnetic-radiation source, a transducer, an electrical power source, a particle source, and a heater, wherein the excitation source is arranged to stimulate the material to generate reactions in the material; and a load comprising a device selected from the group consisting of a heat exchanger, a thermoelectric device, a thermionic device, a thermal diode, a photovoltaic device and a transducer arranged to remove energy generated by the reactions from the material.
a-17e illustrates a reaction process in accordance with the present invention.
g-17h illustrate helium-seeding in accordance with the present invention.
i illustrates deuterium and/or hydrogen loading in accordance with the present invention.
j illustrates sealing of the host lattice in accordance with the present invention.
a-19e illustrates another reaction process in accordance with an embodiment of the present invention.
The accompanying figures further illustrate exemplary implementations according to the present invention.
In the patent application that we present here, we take advantage of several important advances, and also take advantage of a recent breakthrough in our understanding of the basic physics associated with the new phenomena. We now understand why the accepted vacuum picture does not work for a new class of reactions, and we have developed a generalization of nuclear physics that includes the new and old effects on equal footing. If one takes as a foundation that nuclear reactions that occur in a solid should take into account the solid as a fundamental part of the system under consideration, then one is led instead to conclude that phenomena of the type under discussion can and should occur in nature. Moreover, it now becomes clear what the new effects are, how and why the new effects take place, and in the end—what are the important variables that have to this time remained uncontrolled variables, that can now be reasonably controlled by one skilled in the art without undue experimentation.
The question of excess heat and additional questions associated with other anomalies in metal deuterides have been pursued in the interim by a relatively small community of independent-minded scientists, many of whom prior to this affair had unblemished scientific credentials. A series of international conferences on the topic have been held [the most recent ICCF9 at Tsinghua University in Beijing—sometimes known as the MIT of China—in May, 2002]. According to some estimates, on the order of 3000 papers have been written on the topic in all, most of which have not been published in mainstream scientific journals. A large number of experiments have been reported in this period. Many of these experiments have produced positive results, and an equal or greater number have given negative results. Many researchers in laboratories all over the world have seen the excess heat effect. Fusion reactions at low levels have also been claimed, a great many times. Other effects have been reported as well, including: fast particle emission not consistent with fusion reactions, gamma emission, slow tritium production, helium generation in quantitative correlation with excess energy, and the development of large quantities radioactive isotopes within the host metal lattice [K. Wolf, unpublished. Passell, T. O., Radiation data reported by Wolf at Texas A&M as transmitted by T. Passell, 1995, EPRI. (unpublished, but available on the LENR-CANR website)].
Consequently, it might be argued that there exists a substantial database from which to draw upon when considering anomalies in metal deuterides. On the other hand, some of the results that have been claimed over the years have proven either to be not reproducible or in some cases demonstrably incorrect. In science, a determined effort is made within the scientific community to make sure that what is published, and hence accepted, is correct and can be built upon. In the general area of anomalies in metal deuterides, this has proven in general to be very difficult over the years as so many claims that initially looked promising could not be confirmed. This has ultimately produced a situation in which: the mainstream journals in general are not interested in papers in this area; there exists a consensus generally among members of the community studying the problem that there are real effects, but there is much less agreement in general as to which experiments and which effects are right; there is almost no agreement within the community studying the problem as to what might be responsible for any of the anomalous effects. Individual researchers studying the problem rely in general on what they know to be true from their own work, and trust the results of other researchers only to the degree to which they have become convinced by presentations, papers, or discussions. The community does not agree among itself, it has operated in part outside of mainstream science, and individuals within the community each have their own views about what results are right and what is going on.
The ideas described in this patent application follow from a collaborative effort on the part of a number of scientists who have pursued a research program rather different from that contemplated by others in the field. The focus of this effort has been on the basic problem as to what physical mechanisms are involved. The logic being that if one understands what basic physics is involved, then one has the chance of developing experiments and devices by design, rather than by Edisonian trial and error as has been the case for most of the research in the area.
It was recognized early on that the experimental claims presented initially—excess heat and low-level fusion—are not overly useful for clarifying the physical mechanisms involved. The existence of a low-level fusion effect is indicative that somehow deuterons must be getting together, but is silent as to how such a thing might happen. The existence of an excess energy effect is indicative that some new kind of reaction process is operative, but does not provide much in the way of guidance as to what reaction mechanism or physical mechanisms are involved.
Consequently, where some groups focused on trying to perfect the initial electrochemical experiment of Pons and Fleischmann, we focused instead on trying to identify and understand the associated physical mechanisms. Any proposed physical mechanism has corresponding experimental signatures and systematics. We considered more than 100 possible reaction schemes over the course of our research [P. L. Hagelstein, DARPA Report, April 2003]. Schemes were considered, and rejected for either theoretical reasons or experimental reasons, in some case both. A great many experiments have been considered (and many experiments performed) where we have sought guidance on the general problem of mechanism. We have questioned our colleagues about their experiments, and attempted replication of many of these. We have proposed experiments to others, in order to try to prove or disprove one conjecture or another. After 14 years of this kind of process, we have made much progress on the general problem of mechanism, ultimately leading to the inventions discussed here.
We were aided in this effort by some results that have retrospectively appeared to be very helpful. One such result was the observation of low level fast alpha particles in the 18-21 MeV range from PdD loaded by 500-1000 eV deuterons from an ECR (electron cyclotron resonance) source as reported by a group at NRL [G. P. Chambers, J. E. Eridon, K. S. Grabowski, B. D. Sartwell and D. B. Chrisey, “Charged Particle Spectra of Palladium Thin Films During Low Energy Deuterium Ion Implantation,” J. Fusion Energy, Vol. 9, p. 281 (1990)]. This result cannot be understood in terms of vacuum reaction physics as outlined above. This result suggests to us the possibility of a new kind of site-other-site reaction process, in which the energy from two deuterons at one site is used to eject alpha particles from Pd nuclei at another site. The alpha energies expected from this kind of mechanism are in good agreement with the experimental data. We asked other groups to seek confirmation of this result, due to its special importance in illuminating physical mechanisms. By now, there have been at least two other experiments reported which show this effect—one from the Lebedev Institute in Moscow, and one from the group of G. Miley at UIUC [A. G. Lipson, A. S. Roussetski, C. H. Castano, Kim S-O., G. H. Miley, “In-situ Long-range Alpha Particles and X-ray Detection for Thin-film Pd Cathodes During Electrolysis in Li—2SO—4/H—2O,” presented at the March 2002 APS meeting—paper W21.005].
When we finally understood the significance of this result, we began to develop theoretical models that described site-other-site reactions. The basic idea is that reactions that occur in the solid have the possibility of exchanging phonons with the lattice. Reactions at different sites that exchange phonons with a common phonon mode can proceed as a second-order quantum process. The reaction mechanism under discussion might be written as:
(d+d)a+(APd)b→(4He)a+(A−4Ru+α)b
While the theoretical model for this reaction could account for the alpha particle as a primary ejecta, and gave ejection energies in agreement with experiment, the associated reaction rate computed was orders of magnitude off from experiment. We appeared to have part of a piece of the puzzle, but we did not have the whole piece.
If such a site-other-site reaction can occur at all, then it might sensibly be asked what other reactions of this type might be expected. From theoretical considerations, it became clear that resonant reactions in which a reaction at one site is paired with the inverse reaction at another site should be the predominant process of this kind. This led us to consider reactions of the form
(d+d)a+(4He)b←→(4He)a+(d+d)b
In such a reaction, two deuterons at one site come together to make helium, exchange phonons to match the microscopic selection rule. At another site, a helium nucleus dissociates through phonon exchange, making two deuterons. The reaction overall is conservative, no energy is generated to within an excellent approximation. This is illustrated schematically in
We pondered this kind of reaction for quite a while, at first considering it as a somewhat whimsical kind of reaction—as it should be dominant in terms of reaction rate, but it did not seem to be observable as it only seemed to produce an effective exchange of constituents at different sites. For this reason we have termed it a “null” reaction. In time, we recognized that two deuterons created from the dissociation of a helium nucleus would have difficulty tunneling apart, due to the presence of the same Coulomb barrier that kept them from tunneling together in the first place. And if they indeed had trouble tunneling apart, perhaps they could be observed by virtue of being together.
Such an effect can be seen with the aid of a simple one-dimensional analog model. One often develop seeks simplified versions of a complicated many-body model from which the relevant new physics can be seen and studied in isolation from the difficulties associated with the full theory, so that one can understand things simply. In this case, a convenient analog is constructed by replacing the local molecular state with a one-dimensional potential well. The source term due to 4He dissociation appears as an exchange potential. The relevant one-dimensional analog model can be written as
where V(x) is the one-dimensional equivalent molecular potential shown below. We have taken ƒ(x) to be a delta function located near the origin. The strength of the null reactions is modeled in the constant K
When the coupling constant K is large, then a new compact state forms (see
At this point, the significance of an experiment reported by J. Kasagi began to become clear. Kasagi investigated reactions under conditions where an energetic deuteron beam with deuteron energy on the order of 100 keV was incident on a TiD target. The predominant signal was the p+t and n+3He products that would normally be expected from vacuum nuclear physics. In addition, Kasagi saw more energetic reaction products from deuterons hitting 3He nuclei that accumulated in the target—in this case energetic protons and alpha particles. Also in the spectrum were energetic alphas and protons from reactions in which a 3He from a d+d reaction hit another deuteron. All of these reactions are expected. What was not expected were additional signals in the proton and alpha spectrum that had a very broad energy spread. For example, if an incident deuteron hits a 3He nucleus, one expects the energetic protons and alphas to have a spread in energy associated with the momentum of the incident deuteron. This spread is small if the angular spread of the detector is also small. For protons and alphas produced by more energetic 3He nuclei generated in a d+d collision (in which case the 3He is born with about 0.8 MeV of energy), one expects a spread of on the order of 4 MeV above and below the centroid energy in the proton spectrum. Kasagi's measurements showed such a spread for these reactions. But a proton signal with a spread that is much greater is much more difficult to explain. A similar anomalous signal was seen in the alpha channel, where the spread in energy was much wider than could be accounted for by secondary reactions [J. Kasagi, T. Ohtsuki, K. Ishu and M. Hiraga, Phys. Soc. Japan Vol. 64, p. 777 (1995)]. To account for his results, Kasagi conjectured that he was somehow seeing the reaction
d+d+d→p+n+α
Such a three-body reaction gives proton and alpha signals with a very large spread in energy, and with end-point energies consistent with those observed by Kasagi. The spectrum predicted from phase space considerations of such a reaction was consistent with his observations. The only problem is how could it be possible that three deuterons could react with one another? No evidence for this kind of reaction (one with three nuclei reacting in the input channel) had been seen in laboratory experiments before.
We interpreted this experiment initially in terms of the site-other-site reaction described above, in which the deuterons produced by the dissociation of helium have trouble tunneling apart. Hence we viewed the Kasagi experiment as providing support for the emerging theoretical picture under discussion.
Much later, it became clear that the dissociation of helium under the conditions under discussion could also produce localized p+t and n+3He states with an energy matched to the molecular deuterium energy—in fact such states are far more likely in this regard than the two deuteron state initially conjectured. However, this does not change the picture fundamentally. The Kasagi experiment is still interpreted as providing support for the notion that helium can be dissociated as part of a second-order or higher-order site-other-site reaction process, and that the dissociated products can have an energy nearly resonant with that of molecular deuterium. Kasagi has replicated this experiment successfully in a different experimental set-up. It has also been replicated by at least three other groups, one of which was at NRL [G. Hubler, private communication, 2002].
We have taken these ideas much further in our theory effort, as documented in recent conference proceedings and reports. We made progress on the initial formulation of the model by generalizing the Resonating Group Method [J. A. Wheeler, Phys. Rev. 52 1107 (1937)], which was used for the vacuum version of the d+d fusion reaction from the 1930s through the 1980s [J. R Pruett, F. M. Beiduk and E. J. Konopinski, Phys. Rev., Vol. 77, p. 628 (1950). H. J. Boersma, Nuclear Physics, A135, p. 609 (1969)], to include the other nuclei in the lattice at the outset. This generalization is nice in that it includes the vacuum nuclear physics problem as a subset of a larger theory without modification. A similar generalization follows directly for the more powerful R-Matrix method [A. M. Lane and D. Robson, Phys. Rev., Vol. 151, p. 774 (1966). D. Robson and A. M. Lane, Phys. Rev., Vol. 161, p. 982 (1967). A. M. Lane and D. Robson, Phys. Rev., Vol. 185, p. 1403 (1969). R. J. Philpott and J. George, Nucl. Phys., Vol. A233, p. 164 (1974)], although we have not pursued this or other possible generalizations so far in our work.
We have begun to analyze a number of rather fundamental problems associated with the theory. For example, the simplest site-other-site problem is the two-deuteron and helium exchange reaction mentioned above. Our initial analysis indicated that this problem did not produce stable two-deuteron localized states, but that the exchange energy associated with the interaction could be attractive. The conclusion was that two-deuteron localized states could be stabilized under conditions where a larger number of sites and exchange reactions occurred within a common highly excited phonon mode.
Subsequently, we understood that the two-site problem could give stable localized states in the case of the p+t and n+3He channels, with energies that could be nearly resonant with the molecular deuterium state [P. L. Hagelstein, DARPA Report, 2003]. This problem is currently being analyzed, and it has major implications for our basic understanding of the overall process.
We set up a simplified many-site model in order to begin investigating energy exchange between these states and a highly excited phonon mode [P. L. Hagelstein, ICCF9 Conference Proceedings—not yet published; also, the 2002 RLE Report, not yet published.]. The original basic idea is that the exchange reaction discussed above is nearly resonant, except for the exchange of a few phonons that may be different at either site. Hence a single exchange reaction can change the number of phonons present in the lattice. A very large number of such reactions have the potential to produce significant mixing of the nuclear and phononic degrees of freedom. Calculations that we have done indicate that if a relatively small number of localized states and helium nuclei interact with a common highly excited phonon mode, that nearly free energy exchange between the nuclei and the phonon mode becomes possible. We have studied toy models in which the ratio of nuclear energy to phonon energy was allowed to be a parameter that could be varied at will. The coupling of energy in cases where 100, 500, 1000, 2500 phonons respectively were required to match a nuclear energy quantum produced mixed state distributions that were pretty much invariant, suggesting that the coupled nuclear and phonon system is rather efficient at converting nuclear energy to phonon energy.
The model that has resulted from our studies appears to be based on good physics—certainly physics that is more relevant to the problem than the vacuum description presently in use within the nuclear physics community. The many-site version of the model yields a rather rich description of different phenomenon. In the absence of significant phononic excitation, there are no anomalous effects, consistent with a very large number of negative experiments. At weak phononic excitation, such that few phonons are exchanged and little angular momentum is present in the localized states, the model predicts a low-level fusion effect as claimed by Jones.
When higher angular momentum localized states are produced at higher phonon excitation, the model predicts states of the sort seen in the Kasagi experiment, and decay modes with fast alpha ejection, as well as other effects consistent with what has been reported. When enough compact states and helium nuclei interact with a single phonon mode, the model appears to lead to and excess heat effect and associated helium production, again consistent with the relevant experimental observations. This close connection between the model and the different anomalies has been discussed in conference proceedings and reports that we have written.
Ongoing efforts continue to lead to improvements in the models, and we envision that these will lead to useful quantitative design models in the coming year.
We discussed above three fundamental issues raised in 1989 that needed to be resolved in the event that the low level fusion effect and the excess heat effect proved to be real. In light of the theory that we have developed, and also from relevant experimental studies, clear answers are now available.
The basic picture that emerges from this work then is that many of the anomalous effects claimed in experiments with metal deuterides are real, and that these are a direct consequence of allowing for phonon exchange in the basic formulation of the nuclear models. The difficulties encountered by experimentalists within the field are seen to be associated with uncontrolled important variables in the experiments, as most do not have a clear idea of what conditions they are seeking to create in any given experiment. The rejection of the anomalies by the scientific community is seen as a consequence of the relative success of vacuum nuclear physics over the past 80 years in accounting for a wide variety of nuclear experiments, and the expected reluctance of the scientific community to “give up” such a successful viewpoint in favor of a new and unfamiliar picture.
While the development of a significant quantitative design capability remains an ongoing project of interest in our work, the question of what might constitute an eventual practical device is clearly an important one. We are in a position now to begin to address it.
Numerous experiments support our ideas about the physical mechanisms involved. We have retrospectively looked at a great many experiments for which anomalies of one sort or another are claimed, and in essentially all cases we are able to identify how the physical requirements outlined above come into play. Of great interest in this regard are the closely related electrochemical experiments of the early 1990s of K. Wolf and of the SRI group. When the two groups met at EPRI meetings, they were surprised at how they had evolved toward very similar electrochemical protocols for their different experiments. In this case, K. Wolf electrolyzed Pd cathodes in heavy water in order to make neutrons, while the SRI group electrolyzed Pd cathodes in heavy water to make excess heat. Of interest was the dependence of the different effects on the current density. Wolf required current densities in the general neighborhood of mA/cm2 to see neutrons, and got no effect when he drove the system at higher current densities. The SRI group got no excess heat effect at low current densities, but needed to drive the system at higher current densities (typically on the order of 100 mA/cm2) in order to see an excess heat effect. In light of the models that we have described, if we reasonably assume that some fraction of the electrical input power is going into exciting phonon modes in the manner discussed above, then in the Wolf experiment the phononic excitation is relatively weak and the corresponding localized states are relatively unstable, producing dd-fusion products at low levels. In the SRI experiment, the phononic excitation produced at the higher current densities are reasonably presumed to be greater, allowing for much greater phonon exchange and a much greater associated angular momentum in the localized states, which makes them much more stable. In the model, this is required for the system to exchange energy efficiently with the lattice. We note that Takahashi [presented at ICCF9, not yet published] has reported on experiments in which the current is cycled between low levels and high levels, and neutron emission at low levels is observed associated with the low current levels while the excess heat effect is associated with high current levels, consistent with the experiments considered above in this paragraph.
We have outlined in general terms what is essential based on theory, and supported by many experiments, to arrange for anomalies in metal deuterides, and for excess heat in particular. In previous experimental work, the various anomalies come and go with some reasonable level of reproducibility, but the state of the art has not yet produced systems that could be considered either controlled or suitable for commercialization. In seeking a basic understanding of the physical mechanisms, we move toward new systems that work based on design, rather than on trial and error.
In addition to requirements that derive from the underlying theory, we have in addition requirements that derive from other considerations. Some of these are worthwhile to review here.
In what follows in this section we discuss the basic theory behind the inventions described in other sections of the patent application. We recognize that in the course of our work leading to the present application, we have made a rather fundamental advance in our understanding of some very fundamental aspects of how nuclear reactions in a lattice interact with the lattice. In what follows, we will sketch out briefly in a technical discussion the basic principles, models, results and conclusions, as we presently understand them.
We have studied a large number of approaches to the problem of anomalies in metal deuterides over the past 14 years. Most of these approaches did not prove to be fruitful, as might have been expected since the problem is difficult and there is little in the literature that is either helpful or relevant to provide guidance to theory on the problem.
Although it was understood early on that the problem of energy exchange between nuclei and the lattice was critical, it was not really understood until relatively recently how energy exchange might occur in ways that are relevant to experiment. It has only been in the past five years or so that a viable theoretical approach has emerged. From our studies of the new models that result from this basic approach, we have come to the conclusion that these models have predictive capability for experiments on anomalies in metal deuterides.
A requirement that we have imposed from the beginning is that the underlying theoretical formulation was finally arrived at is one that would have to be consistent with the laws of quantum mechanics and with existing nuclear theory. This greatly restricts the approaches possible, and it perhaps might have been possible to foresee the new formulation much earlier if we had had more insight. In the end, the basic formulation that is required is one that generalizes the assumption of a vacuum picture for nuclear reactions, and replaces it by a compelling picture in which the nuclear reactions that occur in the lattice include the lattice as an essential part of the quantum system under discussion.
Once we have adopted the new picture, we require that all subsequent conclusions and predictions follow from the use of pretty much standard theoretical techniques and concepts. Our experience so far with the new formulation indicates that this approach is indeed fruitful, as the predictions of the new model, inasmuch as they differ from the results of vacuum physics, appear to correspond pretty well with the results of experiments that have been reported over the years on anomalies in metal deuterides.
Once we have agreed upon the premise of the new model, it is clear how to proceed, We wish to extend the description of nuclear reactions, historically formulated under the assumption that a vacuum description is adequate, now to include the lattice at the outset. While there exist a few different formulations from which to work, it seems most useful to generalize the formulation that has received the most attention in the relevant literature on the dd-fusion problem. In this case, a perusal of the literature indicates that most papers have made use (either explicitly or implicitly) of the Resonating Group Method of Wheeler [J. A. Wheeler, Phys. Rev. 52 1107 (1937)]. In what follows, we consider briefly the generalization of this method to include the lattice.
In all cases, we seek approximate solutions to the time-independent Schrodinger equation
EΨ=ĤΨ
where E is the energy eigenvalue for the total system, Ĥ is the Hamiltonian that includes a relevant description of the quantum system under discussion, and Ψ is the associated wavefunction. The Resonating Group Method as applied to the vacuum version of the problem presumes an approximate wavefunction Ψt (where the subscript t here is for “trial” wavefunction as is common when using a variational method) of the general form
where the summation over j includes all of the different reaction channels, both input and exit channels. In each channel, the nuclei present are described by fixed nuclear wavefunctions Φj that are associated with channel j. The separation between the nuclear center of mass positions within a given channel j is described by the channel separation factor Fj.
Having fixed the nuclear wavefunctions in this approach, the only freedom available in the variational wavefunction Ψt that might be optimized is in the choice of the separation factors Fj. These channel separation factors can be optimized by requiring that the residual R given by
be minimized. For fixed nuclear wavefunctions Φj, the optimization of the residual leads to coupled-channel equations that are characteristic of the Resonating Group Method
Results consistent with this are given in Wheeler (1937). Coupled-channel equations of this form are either used explicitly or implicitly in association with the dd-fusion problem by most authors from the 1930s through the 1990s. Relevant examples in the literature include J. R. Pruett, F. M. Beiduk and E. J. Konopinski, Phys. Rev., Vol. 77, p. 628 (1950) and H. J. Boersma, Nucl. Phys., Vol. A135, p. 609 (1969).
The primary weakness of the Resonating Group Method with regard to the vacuum formulation of the problem is that the nuclear wavefunctions are not allowed to be optimized. For example, one expects that these wavefunctions will be polarized when they are in close proximity, which cannot be described within this formulation. Further modifications of the nuclear wavefunctions are possible when they are interacting strongly under conditions where the overlap is large. These effects can be described within formulations that are stronger than the Resonating Group Method, such as the R-matrix method [A. M. Lane and D. Robson, Phys. Rev., Vol. 151, p. 774 (1966). D. Robson and A. M. Lane, Phys. Rev., Vol. 161, p. 982 (1967). A. M. Lane and D. Robson, Phys. Rev., Vol. 185, p. 1403 (1969). R. J. Philpott and J. George, Nucl. Phys., Vol. A233, p. 164 (1974).] or the time-dependent Hartree-Fock method. It is possible to generalize the R-matrix method to include lattice effects, but we have not pursued such a project yet at this stage of our research. The reason for this is that all of the different formulations are pretty complicated technically, and we wish to work with the simplest possible formulations that contain the physics of interest before moving on to more complicated formulations.
To generalize the Resonating Group Method to include lattice effects, we require that the channel separation factors Fj be generalized to include other nuclei in the lattice. For example, in the case of the dd-fusion reaction, the Fj would include a description of the relative motion of the two deuterons in a function of the form Fj(R2−R1) where R1 and R2 are the center of mass coordinates associated with the two deuterons. At large separation in the initial channel, this function might be taken to be of the form eiK□(R
When reactions occur in a solid, there are other particles in the vicinity of the reacting nuclei, and we wish to include them as part of generalized channel separation factors. This is readily accomplished through a generalization that we might denote mathematically as
Fj→Ψj
The new lattice channel separation factors Ψj now includes the separation factor of the nuclei that were in the vacuum formulation, as well as all of the nuclei and electrons in the vicinity of the reacting nuclei that might be relevant. In work that we have pursued to date, the contribution of the electrons is included through the effective potential between the nuclear coordinates within the Born-Oppenheimer approximation. But in general, we intend for the generalization here to represent the physics associated with whatever is relevant in the surrounding solid, under the presumption that whatever analysis follows would restrict attention to that which is most important.
This discussion leads immediately to the generalization of the Resonating Group Method, which we can describe mathematically through equations very similar to those discussed briefly above. We take for a trial wavefunction a summation of the form
The trial wavefunction Ψt is now made up of the fixed nuclear wavefunctions Φj that are involved in the different reaction channels of the specific nuclear reaction under discussion, in the same sense as was used in the Resonating Group Method. The new lattice channel separation factors Ψj now include the nuclear separation of the reacting nuclei on the same footing with a description of all of the relevant center of mass coordinates of neighboring nuclei (and electrons if so required in a particular model).
In our discussion of this generalization of the Resonating Group Method in previous publications, we have referred to the new method as the Lattice Resonating Group Method. We have noted previously that the R-Matrix method can equivalently be so generalized.
The new formulation that we have described here is interesting for many reasons. Of great interest is that it includes the old vacuum formulation for nuclear reactions as a subset of a more general theory of nuclear reactions. The new approach is consistent with the large body of accepted experimental and theoretical results obtained previously and accepted by the nuclear physics community. The primary new effect that is a consequence of this generalization is the prediction of phonon exchange associated with nuclear reactions. For example, a fast deuteron incident on a metal deuteride target that reacts with a deuteron in the lattice has a finite probability of phonon exchange as a consequence of the nuclear reaction. This is not taken into account in a vacuum description of the reaction, and we may rightly fault the vacuum description for this deficiency.
Of course, for all first-order reaction processes, the absorption or emission of a few phonons is unlikely to be noticed under most conditions. The associated energy exchange is on the order of tens of millivolts, and the reaction energy is of the order of megavolts. The corresponding impact on the reaction rate or on the final state nuclear kinetic energies is quite small, as expected. This strongly supports the validity of the vacuum description for such reactions.
However, there are new effects that are predicted by the new theory that have been overlooked completely in the vacuum formulation, and which are of interest to us in what follows. Phonon exchange has the potential to contribute to the microscopic angular momentum, resulting in a modification of the microscopic selection rules. Phonon exchange of reactions at different sites with a common highly excited phonon mode can lead to quantum coupling between such reactions, and this opens the possibility of new kinds of second-order and higher-order reaction processes. These new processes appear to be reflected in experimental studies of anomalies in metal deuterides, and are of particular interest to us.
Within the new formulation of the Lattice Resonating Group Method, we now allow for the possibility of phonon exchange in a nuclear reaction, and we must examine in more detail how phonon exchange comes about. In the simplest possible picture, the center of mass coordinates of nuclei must be considered to be phonon operators. We may, for example, write for a nuclear center of mass operator {circumflex over (R)}j an expansion in terms of phonon amplitude operators {circumflex over (q)}
where the summation is over phonon modes in, and the vectors uj,m describe the displacement of the center of mass of nucleus j due to excitation of phonon mode m. It follows that the strong force interaction and Coulomb interaction between nucleons can be interpreted as a highly nonlinear phonon operator when the nucleons are associated with different nuclei. This gives a natural route to the inclusion of phonon exchange in nuclear reactions within a lattice.
Technical issues arise when the nuclear interaction is understood as including phononic contributions under conditions where one of the phonon modes is very highly excited. The motivation for considering this situation is that when the event that the phonon interaction is nonlinear, the second-order interaction between nuclei at different sites becomes algebraic—and hence long range on the nuclear scale. The reason for this is that in a typical quantum calculation of second-order processes where a large number of states are involved, the different states tend to destructively interfere with one another. Off-resonant second-order processes that involve single phonon exchange couple to all phonon modes on more or less an equal footing, leading to severe interference effects that limit the range of interaction. However, in the case of a nonlinear interaction, the coupling to a highly excited mode leads to preferential coupling with that mode, and the strong interference effects normally encountered for linear interactions does not damp the interaction. For this reason, all site-other-site interactions must involve a nonlinear interaction with at least one very highly excited phonon mode.
Unfortunately, this kind of problem leads immediately to technical difficulties. These technical difficulties are discussed in: P. L. Hagelstein, Philosophical Magazine B 79 149 (1999). The highly excited phonon mode is delocalized, and is naturally described in terms of the phonon mode amplitude {circumflex over (q)}, or an equivalent phonon operator. The nuclear interaction is of short range, and is therefore best described in terms of position operators {circumflex over (R)}j. The technical difficulty arises if we try to expand the nuclear interaction in terms of phonon modes, in which case we develop an expansion that must include very high orders of a very large number of phonon modes. Alternatively, if we try to model the dynamics of the highly exicted phonon mode through position operators, our description would naturally require the inclusion of position operators for all of the nuclei involved in the dynamics of the delocalized phonon mode. Neither approach alone appears to be either attractive or particularly useful.
We proposed the use of a hybrid formulation for this kind of problem. The basic idea is to begin with an expansion of the position operator in terms of phonon mode operators, separating out the contribution of the mode that is highly excited
We then define a residual position operator
that includes the contributions of all other phonon modes
This produces a hybrid formulation of the form
where m is understood to refer to the highly excited phonon mode.
The residual position operator
is very nearly the same as the position operator {circumflex over (R)}j. In the event that the separated phonon mode were either unexcited or thermally excited, the difference in operators would be trivial locally. We can make use of this separation between the local and nonlocal degrees of freedom in order to analyze the coupled lattice and nuclear models that arise from the Lattice Resonating Group Method.
We will shortly consider the calculation of phonon exchange in association with nuclear reactions between deuterons in metal deuterides. Prior to this discussion, we require the consideration of a number of practical points that pertain to our discussion. For example, since the tunneling probability between deuterons at neighboring octahedral sites is very low, we are interesting initially in the case of molecular states within the metal deuteride. This reduces the complexity of the associated theoretical problems that we analyze later on. We are interested in the problem of screening between deuterons in a metal deuteride. We conclude from an analysis of the screening problem that the use of the molecular deuterium model in this regard is appropriate (this is the case for titanium deuteride—there is evidence from deuteron beam experiments at low energy that the screening in palladium deuteride and some other metal deuterides is enhanced relative to the molecular case). Finally, we are interested in the distribution of rotational states in the metal deuteride, which is likely to be close to that of the molecular problem.
Early on in 1989 when the Jones effect was first under discussion, there were many manuscripts put forth that discussed the problem of double site occupation in TiD and PdD. The basic issue involved is that the tunneling probability and associated fusion rate for molecular D2 had been explored, with a very low result for both quantities. As tunneling in TiD was expected to be about the same as for the D2 molecule, it appeared that the Jones effect could be ruled out based on such theoretical considerations. Subsequent measurements of dd-fusion cross section for low energy (keV) deuterons incident on TiD targets gave deviations from the free space fusion cross section for bare ions that were consistent with screening at a level commensurate with the molecular D2 problem.
There was further discussion in 1989 that deuterons occupied primarily octahedral sites in PdD and tetrahedral sites in TiD, and that these deuterons were on average further apart than in molecular D2, and hence would have a smaller associated tunneling probability. These questions were of interest to us over the years, as many speculative papers appeared suggesting that the physics might be otherwise. In addition, when we began focusing on schemes based on dd-fusion reactions, these questions began to become important for our work. We were interested in the basic question as to what conditions give rise to the largest tunneling rate in PdD. The basic issue in question is that to achieve tunneling at the molecular D2 level, it would seem that a molecular version of the D2 molecule would need to be present within the metal deuteride. In the case of double occupancy of a site, perhaps the associated D2 wavefunction could be approximated by a molecular wavefunction, modified in some way to account for the potential of the surrounding host lattice atoms. Given that the probability for double occupancy in bulk PdD is very low, the associated question arose as to what is the tunneling probability associated with deuterons in neighboring sites. In response to this, we developed two-deuteron variational wavefunctions for the problem of two deuterons in a metal deuteride given by
We studied this problem using wavefunctions of the general form
Ψ(r1r2)=φa(r1)φb(r2)g(r2−r1)
as well as with more sophisticated trial wavefunctions. As perhaps might have been anticipated, we found that the tunneling probability associated with deuterons at neighboring sites was astronomically low. The potential barrier associated with realistic potential models is sufficiently high and wide that it introduced tens of orders of magnitude reduction in the tunneling rate over that of the molecular problem. This was true for O-O, O-T, and T-T occupation. We considered separately the cases in which a deuteron at one site tunneled to a neighboring site, and where deuterons from both site tunneled in order to meet in the region between sites. We also studied cases in which two deuterons were situated at the same site, in both octahedral and tetrahedral sites. We found in these cases that the wavefunction was approximately molecular, and that the overlap probability was maximized relative to all other cases.
The basic conclusion is that any reactions involving two deuterons in metal deuterides must involve the molecular D2 state within the metal. A retrospective analysis of the different conditions under which anomalies have been reported suggests that in all cases the highest level of anomalies are reported in metal deuterides in which the molecular D2 content is maximized. For example, in electrochemical experiments at SRI, the loading is maximized such that the deuterium concentration exceeds the Pd density near the surface—conditions that would maximize double occupation of a site. Double occupancy is also maximized in the presence of host metal lattice vacancies, and many successful experiments have been reported in materials that would be expected to have very high defect densities. In some cases, experiments operate at elevated temperature with relatively low loading, with positive results. In such cases, the elevated temperature combined with lattices containing large concentrations of defects would maximize double site occupation. We note in addition that host metal lattice vacancies are thermodynamically favored in highly loaded PdD and NiD (Fukai used this feature to create metal hydrides with one out of four host metal lattice atoms missing), such that they will diffuse inward from surfaces at slow rates. We conjectured that this mechanism might have been responsible for a long time constant associated with the excess heat effect in the early SRI experiments.
Over the years, numerous authors have suggested that the Jones experiment could be accounted for through an enhancement of electronic screening effects in titanium deuteride. For example, it is known that in semiconductors and in special classes of materials, electrons behave as if they have a mass greater than the free electron mass. An increase in the electron mass, according to the argument, would produce an enhanced screening effect, which might increase the fusion rate. This kind of argument is not correct, as the screening required must occur under conditions when the two deuterons are within less than an Angstrom. The electron band theories that lead to an apparent modification of the electron mass apply for electrons delocalized over many sites, and are not applicable for this kind of screening.
Ichimaru published in Reviews of Modern Physics a computation of screening between deuterons in PdD and TiD based on relatively sophisticated models that are used in astrophysics. Based on his calculations, he concluded that the tunneling probability is increased by on the order of 50 orders of magnitude from the results of the molecular problem. If true, this would be a very important contribution, and might help to shed light on the problem of anomalies in metal deuterides generally.
In Ichimaru's model, the effect that contributes the largest amount to the screening is a model for the static dielectric constant used within the effective Coulomb interaction. We were unfamiliar with the use of a dielectric response other than the vacuum dielectric response in the case of deuterons close together within the lattice.
To investigate this, we developed a version of a linear response model for the electrostatic interaction between two deuterons in metal deuterides. The result can be expressed in the form
The dielectric response comes about naturally in infinite-order Brillouin-Wigner theory. We were interested in whether this response resulted in a modification of the Coulomb interaction at short range. At long range (under conditions where many atoms and electrons are between the two deuterons), this kind of model reproduces the dielectric response used by Ichimaru.
From an analysis of this model, we concluded that the screening effect at short range that follows from this model produces a polarization potential of the form
V
pol
=V
o
+ΔR·M·ΔR
where ΔR=R2×R1. The dielectric response from the electrons localized at other atoms yields only a weak screening locally between the deuterons. Based on this, we conclude that the dielectric response at short range should be the vacuum dielectric response. We disagree with the results of Ichimaru in this regard.
The tunneling between deuterons that are in molecular states within the metal deuteride is dependent on the vibrational and rotational excitation. As the vibrational excitation energy is significantly greater than kBT, our interest in this regard is on the excitation of the angular momentum states. Plotted below in Figure Th-1 are shown the fractional populations of the different rotational states of molecular deuterium from a calculation that we have done [for a discussion of this kind of calculation, see P. L. Hagelstein, S. D. Senturia and T. P. Orlando, Introduction to Applied Quantum and Statistical Mechanics, to be published shortly by Wiley and Sons]. One sees that the distribution is limited to states of relatively low excitation as would be expected from the moment of inertia of molecular deuterium.
In many experiments on anomalies in metal deuterides, it is arranged so that a deuterium flux is present within the metal deuteride. It might reasonably be asked as to whether such a flux can modify the distribution of angular states as estimated for molecular deuterium as calculated above.
To examine this possibility, we require an estimate for what deuteron velocity might be relevant in order to contribute angular momentum, as well as an estimate for what the corresponding deuteron flux might be when some fraction of the deuterons have such a velocity. We begin by examining the velocity. In a semi classical model, we might estimate the velocity needed from equating the classical angular momentum to a quantum unit of angular momentum. The classical angular momentum is
L=r×p
Assuming that the velocity and momentum are perpendicular leads to the semi-classical constraint
r(Mv)=l
where M is the relative mass, r is the separation and v is the velocity. In this case, we assume l units of angular momentum. Evaluation of this indicates a need for velocities on the order of several hundred cm/sec per unit of angular momentum.
The deuterium flux is perhaps most meaningfully characterized in terms of the associated current density J, which can be estimated by:
J=qNv
If we assume that all of the deuterons in a nearly completely loaded metal deuteride participate, we conclude that the current density required is on the order of 6400 v in units of Amps/cm2, which is an extremely high current density that is orders of magnitude greater than current densities thought to be present in experiments within the field. If one presumes that only a small number of deuterons are mobile, then the calculation is improved by the fraction assumed to be mobile—nevertheless, the resulting numbers are in the tens of thousands of Amps/cm2 equivalent of deuterium flux, which is outside the range of average currents in the experiments. We conclude that the presence of a deuterium flux at accessible levels does not alter the angular momentum distribution significantly.
Having described the premise of the new formulation, and having considered some of the practical issues associated with deuterium in metal deuterides, we now need to consider the issue of phonon exchange in nuclear reactions. In the prototypical model under discussion, we assume that there is a single very highly excited phonon mode present in the metal deuteride that interacts with the nuclei in the metal deuteride. For energy production, we are interested in reactions between two deuterons, and more generally between all of the mass 4 states that are accessible. If we wished to expand our discussion to the problem of fast alpha emission, we would also need to consider the interaction of phonons with alpha particles in the host metal nuclei. To expand further to the case of induced radioactivity as reported by Wolf, we would include phonon interactions in association to reactions mediated by the weak interaction. For simplicity, in what follows we will focus on phonon interactions in selected transition associated with the mass 4 states, recognizing that the approach applies generally to a much larger class of reactions.
Some consideration of nuclear models is appropriate in this discussion. We are considering a nuclear description in which protons and neutrons are taken as fundamental particles (the details of the internal quark structure is not essential in the physics under discussion here). Nucleons interact with one another primarily through the strong force at close range, and through the Coulomb interaction at longer range (since the strong force is short range). The interactions of interest to us are well described through a parameterization of the strong force interaction appropriate to the low energy regime. In this regard, we expect that a description based on a Hamada-Johnston type of nuclear interaction model would be appropriate.
In our work so far, we have explored phonon interactions using simpler models. Part of our effort has been devoted to improving the models so that we are able to analyze phonon exchange directly with realistic nuclear potentials (such as the Hamada-Johnston potential)—our first results of this kind are expected within the coming year. The calculations that we have done so far are based on Gaussian wavefunctions and scalar Gaussian potential models for the strong force. Such calculations so far confirm the important aspects of the theory under discussion, and give results that we would expect to be correct qualitatively.
Many important features of atomic and nuclear processes derive from the associated selection rules, and there are some associated issues that we need to address here. We assume that the dominant interactions involved in the processes under discussion are due to strong force interactions, under conditions where the difference of center of mass coordinates are made up of a phononic contribution (due to the highly excited phonon mode) and a residual contribution (due to all the other modes). The strong force interaction in the absence of phonon exchange conserves isospin, spin and spatial symmetry of the nuclear wavefunctions. Isospin conservation is retained when the highly excited phonon mode is included explicitly in the calculation, but spin and spatial symmetry is not. Spatial symmetry of the nuclear wavefunctions can be changed in association with a change in the symmetry of the phonon wavefunction in the amplitude space (q configuration space). Spin can be changed due to the presence of LS interaction terms in the strong force interaction under conditions where the spatial operators include phononic contributions.
Consequently, in the mass 4 problem, if we are interested in reactions leading to 4He, we are restricted to nuclear channels with zero total isospin. As deuterons have isospin T=0, and 4He has isospin T=0, the isospin selection rule has an impact on the accessible two-body t+p and n+3He channels, as well as whatever excited helium states that one might consider including. The spin channels are in general unrestricted, and the channels with different spatial symmetry are restricted only in the requirement that the total nuclear local nuclear 4-particle fermionic wavefunctions must be antisymmetric under particle exchange.
We recognize that phonon exchange can contribute angular momentum to the microscopic nuclear system, so that we anticipate phonon-induced modifications of the vacuum selection rules. For example, two deuterons can fuse to make 4He in vacuum with the emission of a gamma in an electric quadrupole electromagnetic transition. In the lattice, the exchange of an even number of phonons greater than zero can make satisfy the selection rules with no need for a gamma. The situation is qualitatively similar as in the case of phonon emission associated with electronic transitions of atomic impurities in a lattice. An atomic transition that in vacuum can proceed through radioactive decay with a dipole allowed transition can instead decay through a dipole allowed phonon emission process.
The general theory under discussion is a completely standard quantum mechanical treatment of a coupled quantum system (in this case a coupled phonon and nuclear system), and hence the coupling between the phononic and nuclear degrees of freedom comes about directly from a calculation of the interaction matrix element. The degree to which we are able to make quantitative predictions and qualitative statements about the physics under discussion is in proportional to our ability to estimate such interaction matrix elements.
In our work so far, we have focused on the calculation of interaction matrix elements for the special case of phonon-induced transitions between two deuteron states and the 4He ground state. These calculations were performed in support of our efforts at evaluating a model based on transitions between the molecular D2 state, two-deuteron compact states and the 4He state. We will shortly describe the details of this calculation, but before doing so we must note that since these calculations were done our understanding has improved. Consequently, we intend here to use the result from this calculation instead as an approximation for the interaction associated with a different reaction process.
Keeping this in mind, we then consider the evaluation of the interaction
ΦddφnYlm|Ĥ−E|φHeφn′
which first appeared in our work in the analysis of the two-site problem associated with the null reaction
(d+d)a+(4He)b(4He)a+(d+d)b
In the two-site problem, we assumed an initial wavefunction that included the different angular momentum channels of the two deuterons states (in a scalar approximation with no spin or isospin) and a highly excited phonon mode
This model is discussed further in P. L. Hagelstein, “A unified model for anomalies in metal deuterides,” ICCF9 Conference Proceedings, Beijing, May 2002, edited by X. Z. Li (in press). To estimate the nuclear interaction including phonon exchange, we adopted simple models for the nuclear states of the form
Φd=N2e−β
ΦHe=N4e−β
The use of these kinds of states in the early nuclear literature in the 1930s was common. The 4-particle wavefunction is sometimes called a Feenberg wavefunction.
The overlap integral between a deuteron pair and a helium nucleus depends on the relative distance between the deuteron center of mass coordinates. If we naively replace H-E by an attractive scalar Wigner interaction, then we obtain
Where x21=r2−r1 and x43=r4−r3. The distance between the two-deuteron center of mass coordinates is a function of the amplitude of the highly excited phonon mode
Here
After much algebra and the use of the WKB approximation, we obtain for an interaction
where Δn is the number of phonons exchanged, and where
Our calculations so far indicate that a maximum local relative motion |Δu|qmax on the order of half a fermi is sufficient to generate a significant two-phonon exchange interaction. Relative motion on the order of several fermis can result in the exchange of on the order of 10 phonons within this kind of model. Results for this model are illustrated below in
For the specific model that we investigated, we took the values
V0=36.0 MeV
α=0.2657 fm−2
β4=0.07942 fm−2
The calculation of the nuclear interaction including phonon exchange as outlined above would be a reasonable approximation in the event that the local relative motion of the two deuterons is linear. When we documented this model, we noted that the contribution to the relative motion of the two deuterons due to the highly excited phonon mode (Δu q) would have to be obtained through a separate calculation involving the linearization of the potential between the two deuterons. We recognized subsequently that this problem is more interesting than would be implied by the computation outlined above.
Two deuterons interacting with one another through the Coulomb interaction experience very strong radially directed forces when close together. Consequently, a linearization of the associated classical problem shows that there is almost no radial motion (since there is such a large gradient in the radial Coulomb potential), but instead the motion should be angular. A weakness of the model as presented for the two-deuteron problem is then in the use of a linear model for relative phonon-induced motion instead of an angular model. The phonon exchange that would be expected from a model improved in this way is less than for the linear model used. We have not yet developed such a model, but we would expect such a model also to give a significant phonon exchange effect.
More recent work has pointed to the importance of the p+t and n+3He channels as candidates for the comprising the compact states of the model (and that appear in the Kasagi experiment). A consideration of the p+t channels indicates that the local relative motion associated with a highly excited phonon mode would also be angular as discussed above for the two-deuteron channel. However, the n+3He channels are different. Since the neutron has no charge, there is no Coulomb interaction, and a linear model for relative motion is far more relevant. In this case there will still be primarily angular motion for small separation, but overall the linear trajectory should be a much better approximation. The details of the computation will differ, since the triton wavefunction is more localized. Nevertheless, we expect the associated interaction potentials
Φn
and
Φn
to be similar in terms of how the phonon exchange works. In the first case, the phonon interaction in the case of n+3He and 4He states can be understood simply. Associated with the strong excitation of the highly excited phonon mode, a 4He nucleus will “move” locally in accordance to
The 3He of the n+3He channel will see a similar solid state environment, and its dynamics are described by.
The displacement vectors uj are naturally different since the mass is different in the two cases. Hence the differential displacement Δu in this case in the approximation of a linear trajectory is due to the difference between the amplitude of vibration associated with the different species. In this case, one would expect the uj vectors to occur in the ratio of the square root of the inverse masses. Within this model, one calculates that sufficient phonon exchange occurs when the maximum total amplitude of vibration due to the highly excited phonon mode is on the order of 50-100 fm, as the maximum relative displacement in this case is less than this by (1−√{square root over (3)}/2)=0.134.
More sophisticated models for the relative trajectory of the two nuclei would likely lead to a lesser fraction of the total amplitude of motion to be expressed as relative motion at close range, but at present it is thought that the basic argument is correct, but that the total range should perhaps be two orders of magnitude greater than 5-10 fermi presently thought to be the scale of a compact state, instead of one order of magnitude as in this case of a linear trajectory.
We studied a scalar Gaussian model for the two-site problem for a version of the null reaction
(d+d)a+(4He)b(4He)a+(d+d)b
as mentioned above. The question at issue in the analysis was whether this model leads to a localized two-deuteron state with an energy below that of the molecular state. Our analysis of this problem at the time indicated that the exchange interaction was in fact attractive for some of the states, but not sufficiently attractive to stabilize a two-deuteron compact state.
The basic argument is worth discussing. A two-deuteron compact state would have a nuclear energy associated with the Φj basis states that are the same as for the molecular D2 state. In addition, there are contributions associated with the strong force interaction between the deuterons, the Coulomb interaction, the radial kinetic energy associated with localization, and the centripetal energy. Within the model under discussion, there is also an exchange energy associated with the null reaction. The total two-deuteron compact state energy is then
If we assume that the compact state involves nuclei separated enough that the nuclear “optical” potential can be neglected, then it must be arranged so that the Coulomb, radial kinetic and centripetal energies are balanced by the exchange energy. If we adopt a Gaussian and power law model for the compact state wavefunction of the form
Pl=rl+1e−γr
then we find for the three positive energy terms the result
(p+t)a+(4He)b(4He)+(p+t)b
involving compact states at the two sites is quite interesting. In this case the compact state energy is
which is about 4 MeV lower than in the case of two-deuteron compact states as discussed above. It is much easier for this kind of state to be stabilized.
Similar considerations apply in the case of an n+3He compact state, although the nuclear energy difference is a bit less.
One advantage of the n+3He compact state is that the mechanism for phonon exchange outlined above is expected to be more effective in the event that one of the constituents in neutral, as a neutron does not participate in the lattice phonon mode structure. Our current speculation is that such states may be the dominant compact state for this reason. This conjecture remains to be proven, but seems to be reasonable at present.
The discussion of these states as possibly being stable if there energy lies below the molecular D2 state energy requires some comment. It is clear that all such localized states with an energy greater than the p+t rest energy are unstable against conventional fusion reactions that produce p+t as reaction products. The idea here is that phonon exchange in the models under discussion is very efficient in the limit that (Δu qmax) is on the order of 10 fm or larger, so that the phonon-induced reactions under discussion can couple to high angular momentum states. We have estimated the reduction of the tunneling in the presence of angular momentum in the case of n+3He decay at the d+d rest energy. The results are illustrated in
As a consequence, the models under discussion will be very stable when such large angular momentum transfer occurs, and this provides the theoretical basis for our requirement on significant phonon excitation. We need to transfer 20 or more units of angular momentum, or else there is little possibility of arranging for sufficiently stable compact states to exchange energy with the lattice. The ideas presented above apply in principle to the p+d reaction as well. In this case, the null reaction becomes
(p+d)a+(3He)b(3He)a+(p+d)b
One candidate for the compact state in this case is a p+d state. In light of the discussion above, we are motivated to consider other possible compact states in which a neutron is free, so that the phonon exchange might be maximized. The mechanism described above that involves a free neutron would produce initially a compact 2He+n configuration that would be expected to couple to p+p+n configurations. These possibilities have been proposed in the course of our work, but as yet we have not attempted models that are specific to this problem.
Assuming that the basic mechanisms discussed above and below carry over to this reaction, then we are in a position to make some comments about the theory that is implied. The p+d reaction in vacuum produces 3He through an electromagnetic decay, and there are no kinetic reaction pathways. High angular momentum in this case stabilizes the compact state, as higher multipole radiation is then required to produce the singlet 3He ground state. However less angular momentum would seem to be required to achieve stable compact states than in the case of the d+d reaction. For example, here we are probably set with on the order of 10-12 units of angular momentum, whereas we would like 20 or more for the d+d reactions. Support for this idea comes from experiment in the lower current densities historically required for heat production in light water cells, which we interpret here as being based on the p+d reaction.
The lighter reduced mass translates into a faster reaction rate, all else being equal, as the tunneling probability for the proton and deuteron is increased by orders of magnitude. This will become important shortly.
The only potential disadvantage of the p+d reaction is that the reaction energy is about 5.5 MeV, instead of 23.85 MeV for the d+d reaction. One makes better use of deuterium in this kind of reaction.
Our studies of the two-site problem so far have shed light on many important issues. It is useful to summarize the results in light of the most recent modeling efforts. The two-site problem shows clearly the presence of exchange terms that derive directly from the Lattice Resonating Group Method (coupled-channel radial equations are given explicitly in P. L. Hagelstein, “A unified model for anomalies in metal deuterides,” ICCF9 Conference Proceedings, Beijing, May 2002, edited by X. Z. Li (in press). Moreover, we analyzed using simple scalar Gaussian models the interaction including phonon exchange in the presence of a highly excited phonon mode. The analysis of the resulting states showed clearly exchange effects that could be attractive.
Subsequent to the initial work on the problem, it has become clear that the two-site problem contains more as well. In the event that the angular momentum exchange is sufficiently large as to stabilize the states through the centripetal barrier as discussed above, then we might consider the compact states to be stable at different energies than we considered initially. For example, we would consider a high angular momentum state to be stable for many practical purposes if the state energy were a few MeV above the two-deuteron energy as long as all possible decay modes were sufficiently suppressed. The two-site problem in this limit then does describe stable compact states in a nontrivial limit. This is interesting, and advances the discussion in comparison to what we have written so far on the problem.
Nevertheless, we are interested in energy production, and within the framework of present understanding, the two-site model does not lead to heat production. We are therefore motivated to extend the discussion to the many-site version of the problem.
There are a number of technical issues that we face in the many-site problem. The first issue is that the complexity quickly increases as the number of sites increases. Consequently, we must explore the use of approximate methods and models that are somewhat idealized. The second issue is whether energy can be exchanged effectively between the nuclei and the lattice. Our models so far indicate that there exists a mechanism which accomplishes this, and we will address this below. Finally, there is the question of the associated reaction rate, which is where we will conclude our discussion.
We have developed models that address different aspects of the many-site problem. The increase in the stabilizing exchange energy as a function of the number of sites can be established directly through explicit construction of approximate solutions to the associated coupled-channel equations. This is documented in a recent (unpublished) final report for DARPA, and will be written up for publication in the coming year. We have developed in addition a many-site model that assumes that the phonon interaction is uniform at a large number of sites, and that the projection into the different compact states is also uniform at the different sites. Massive energy exchange between the nuclei and the highly excited phonon mode has been demonstrated with this model.
At present we are in the process of developing a new class of more sophisticated models that will address the problem of reaction rate. From our understanding of other models, it seems reasonable to attempt to extract an overall reaction rate estimate from this kind of model, as we will discuss shortly.
We first consider many-site models that assume spatial uniformity. The mechanics of the construction of the many-site coupled channel equations are straightforward, however, the problem seems to be qualitatively richer as we discuss below. The many-site coupled-channel equations are of the basic form
where PMβ is a many-site channel separation factor with configuration β and with index M defined by
There are a very large number of channels, and it quickly becomes impractical to attempt a direction solution of them. In our previous work, we made use of infinite-order Brillouin-Wigner perturbation theory in order to get some insight as to possible nature of the solutions. Here, we simply note that it appears that such an approach is simply not up to the problem when the coupling becomes strong enough to be interesting in terms of accounting for the experimental results. Instead, we must make use of alternate approximations.
Of fundamental concern is the question of whether there exist localized solutions to the many-site version of the coupled-channel equations. It seems a priori unlikely that an answer would be forthcoming without a brute force computation on the coupled-channel equations. Our efforts to date on this problem have so far not produced insight. For the purposes of the present discussion, we might adopt as an ansatz the assumption that we can define useful localized states that may or may not be stable, and proceed with the calculation in order to ascertain the goodness of the ansatz with solutions in hand. This has proven to be a productive approach.
We simplify matters further in order to allow us to make progress on the development of this very hard problem by assuming that all sites are identical, and furthermore, that the establishment of a localized state at each of these sites will involve the same local superposition of orbitals within the different angular momentum channels. These simplifications lead ultimately to a an approximate time-independent eigenvalue equation based on a Hamiltonian of the form
In this Hamiltonian the {circumflex over (Σ)} operators are pseudospin operators that are developed as a superposition over Pauli matrices at the different sites
The parameter S is the Dicke number for the system
The localization energy for a single site is and the Vnn′ terms are integrals of the interaction potentials and localized orbitals summed over the different angular momentum channels. The {circumflex over (δ)}nn′ operator changes the number of phonons in the highly excited phonon mode.
We have encountered such a Hamiltonian previously, before we had considered the possibility of localized two-deuteron states, as perhaps applying to a many-body version of the problem in which molecular states would make phonon-mediated transitions to helium states. In that case, the hope was that the number of sites involved would be sufficiently large that the Dicke enhancement could offset the Gamow factors. Here, we apply the Hamiltonian now to the situation where compact states are making transitions, in which case there is no Gamow factor, and the coupling is very strong. In our previous work, we studied this kind of model in order to understand under what conditions such a model might lead to extended states that were sufficiently broad in n so as to allow coherence between the states with different number of fusion events and vastly different phonon number such that approximate energy conservation occurred. We were astonished at how this model stubbornly insisted on producing localized states in which the number of phonons exchanged was on the order of the associated dimensionless coupling constant. This being said, we are aware that the eigenfunctions of this Hamiltonian are generally not overly interesting in regards to relating to the physical problem in question, without further input to the problem.
The basic problem with the model Dicke Hamiltonian lies in its high degree of symmetry when n and S are large, and M is small. In order to develop delocalized solutions, the symmetry needs to be broken somehow. Either we require coupling coefficients that depend strongly on n or M, or else we need some kind of additional potential that is highly nonlinear in one or both of these quantum numbers.
There is another effect which is much more important, and which has a very strong dependence on M. This includes loss terms. For example, when two deuterons fuse in the many-site problem, the off-resonant energy ΔE (24 MeV) is more than enough to fuel recoil between localized deuterons and many other highly energetic decay modes. The presence of such decay modes completely destroys the underlying symmetry of the problem, and produces significant delocalization of the wavefunction in n and M space.
Unfortunately, the inclusion of decay channels into a Hamiltonian is not particularly straightforward. Such problems in other disciplines are often handled using density matrices. We wish not to adopt such a formulation here, as the associated complications would likely make further progress more difficult due to the added complexity of the approach. Instead, we prefer to think about the problem as a probability flow problem, as we will outline below. This discussion will appear shortly in P. L. Hagelstein, “A unified model for anomalies in metal deuterides,” ICCF9 Conference Proceedings, Beijing, May 2002, edited by X. Z. Li (in press).
In order to derive the relevant flow problem, we consider a Hamiltonian of the form
H=H
0
+V
We imagine that the problem divides up into three sets of basis states, source states, sink states, and states intermediate between the two. For example, we might consider deuteron pairs locally in molecular states to be part of the source states. States that contain energetic reaction products that result from recoil processes or other reactions are sink states. Intermediate states are those including helium nuclei or two-deuteron compact states in the sites of interest. We may divide the associated Hilbert space into three sectors that correspond to source basis states, sink basis states, and intermediate basis states. After all, loss can be thought of as simply transitions from a sector of Hilbert space that one is interested in, to other sectors. We can accomplish this splitting of the different sectors by taking advantage of Feshbach projection operators
where the summation j is over the basis states in sector i. The time independent Schrodinger equation for this Hamiltonian is
EΨ=H
0
Ψ+VΨ
To split this equation into sector-dependent equations, we assume that the eigenfunctions contains components in the three different sectors
Ψ=Ψ1+Ψ2+Ψ3
The time-independent Schrodinger equation is then divided into sector-dependent equations given by
EΨ
1
=H
1Ψ1+V12Ψ2
EΨ
2
=H
2Ψ2+V21Ψ1+V23Ψ3
EΨ
3
=H
3Ψ3+V32Ψ2
We identify Ψ1 with the source sector, Ψ2 with the intermediate states, and Ψ3 with the sink states. In writing these equations, we presume that there is no direct coupling between source and sink states. The sink states can be eliminated as in infinite-order Brillouin-Wigner theory
Ψ3=[E−H3]−1V32Ψ2
The intermediate sector equation then becomes
EΨ
2
=H
2Ψ2+V21Ψ1+V23[E−H3]−1V32Ψ2
The interaction between the intermediate sector and the sink sector appears in this equation in the same way as in infinite-order Brillouin-Wigner theory. When the resolvant operator has a pole in a continuum at energy E, then the inverse operator develops an imaginary component that describes decay. We see in this equation a description of the intermediate sector, driven by the source sector, and decaying to the sink sector. We can solve formally for the intermediate sector component of the wavefunction to obtain
Ψ2=[E−H2−V23[E−H3]−1V32]−1V21Ψ1
This accomplishes the development of a probability amplitude flow equation, complete with source and with sink. Although the underlying formulation is rigorously Hermitian throughout, the inverse operator describing the intermediate sector evolution is non-Hermitian with respect to the intermediate sector. We have included loss into a Schrodinger formulation in a useful way. We define the operator K2 to be the intermediate sector Hamiltonian augmented with loss terms that are non-Hermitian with respect to the sector 2 basis states
K
2
=H
2
+V
23
[E−H
3]−1V32
The intermediate state solution written in terms of this operator becomes
Ψ2=[E−K2]−1V21Ψ1
This is interesting, as K2 has eigenfunctions that are delocalized due to the presence of loss terms that are very nonlinear in M.
We have put together a computer code to analyze the intermediate state solutions along the lines outlined above. Let us consider a few examples in order to illustrate some of the systematics. In
In
The many-site version of the problem is very rich, as we see from the discussion above. We have achieved some measure of success in understanding the physical content of the new models through direct solution of the quantum flow problem associated with the relevant Dicke Hamiltonian augmented with loss. The symmetry associated with the basic Dicke Hamiltonian prevents efficient coupling between the nuclear and phononic degrees of freedom of interest to us. But as demonstrated above, the inclusion of loss in the model allows for this symmetry to be broken, and we find that massive coupling of energy between the nuclear and phononic degrees of freedom results from this kind of model.
Our models have so far not focused on the issue of the reaction rate that might be expected. This is to some degree the last issue to be addressed in regard to our theoretical efforts. The ideas and models that we will describe are presently areas of research that we are investigating. Consequently, our discussion is by necessity somewhat less complete than the work documented above.
The ability of compact state nuclei to exchange energy with the lattice we take as established through the arguments given above in this discussion. The relevant question then is how does one arrange for deuterons (or protons and deuterons) to get from molecular states to the compact states? This issue is of course addressed formally within the Lattice Resonating Group Method and the associated coupled-channel equations, and any analysis of the problem derives from a consideration of the solutions of the equations.
However, we are in search of intuition as to what the models say as to how this happens. We have recently identified a misconception in this area that is worthy of discussion here. Our intuition in the last few years has been that we can modify the probability distribution associated with the molecular state at small radius through the exchange interaction described above. Although we have verified that this is true, it unfortunately does not appear to be sufficient.
To understand a complicated many-body problem, one usually likes to have a simple analog model, which contains the relevant physics, so that one can understand things simply. In this case, a convenient analog is constructed by replacing the local molecular state with a one-dimensional potential well. The source term due to 4He dissociation can be approximated as an exchange potential, leading to
where V x) is the one-dimensional equivalent molecular potential
We have taken ƒ(x) to be a delta function located near the origin. The strength of the null reactions is modeled in the constant K. This is illustrated above in Figure Th-c. This analog model problem is easily solved [see Figure Th-d]. When the coupling constant K is small, the solutions consist of states that are very close to the bound states of the well that contain a small amount of admixture from a localized state near the origin. The associated intuition is that the deuterons spend part of their time in the molecular state, and part of the time localized. We associate the localized component as being due to contributions from deuterons at close range that are produced from helium dissociation, which tunnel apart. We note that this basic argument applies whether the exchange occurs with two deuteron states, or with localized p+t or n+3He states.
We used this box model to estimate the level splitting that would be obtained under conditions of precise resonance between the compact state and the equivalent of the molecular state. The basic idea is that at resonance, the compact state and the ground state of the well mix maximally, producing two states—one that is a superposition of the two states in phase, and one that is a superposition of the two states out of phase. The associated dynamics for a two-state problem then is governed by the energy splitting between the two states. If the system is prepared initially in the bound state of the well, it will oscillate between the compact state and the delocalized state. The rate of oscillation then is determined by the energy level splitting.
We computed the level splitting exactly analytically, as documented in the DARPA final report. The result is complicated, but in essence it is of the form
Δ∈˜voe−G
where e−G is the Gamow factor associated with tunneling, and v0 is the strength of the potential at short range. This kind of resonance allows for a vast improvement in the tunneling rate over what would be expected from a Golden Rule calculation (assuming that the potential near the origin was involved in an incoherent process) of
The difference between e−G and e−2G can be enormous in the event of a thick and high potential barrier.
We have examined a similar calculation in the case of the radial molecular potential for D2. In this case we studied the radial Schrodinger equation
using for the potential V(r) the empirical potential of Frost and Musulin. We computed solutions under conditions of resonance between the localized state and the molecular ground state in order to understand the associated energy splitting, and hence the dynamics under resonance. We carried out computations for different placements of r0, in each case optimizing the resonance condition. Numerical computations of this kind are limited by the numerical precision, however, the scaling is clear from the results illustrated in Figure Th-10. The results are not surprising in light of the analytic results for the equivalent box model. The results are consistent with an energy splitting on the order of
Δ∈˜voe−G
where v0 is on the order of the Coulomb potential at the location of the exchange potential.
The energy splitting is seen to be on the order of (105)(10−37)=10−32 eV. This is both good news and bad news. The good news is that the associated frequency is on the order of O(10−17) sec−1 which is orders of magnitude faster than any possible incoherent version of the tunneling process. The bad news is that the number of practical problems associated with this kind of resonant state mechanism is enormous. For example, we would require that the two states be in resonance to within an energy on the order of the splitting, which is problematic. To achieve the fastest Rabi oscillation rate, one would have to wait a very long time, as the probability in the target state is quadratic in time. And if somehow all of these problems could be surmounted, one requires a correspondingly long dephasing time to implement a coherent transition of this type.
The discussion above makes clear certain aspects of the problem that are of interest to us in the discussion that follows. The first is that coherent processes can achieve a dramatic enhancement in reaction rate over incoherent processes, especially when the difference between e−G and e−2G is many orders of magnitude. Within the context of the present discussion, it is clear that no incoherent mechanism could possibly lead to reaction rates that are within tens of orders of magnitude of those claimed in experiment. Hence whatever mechanism is to be discussed, it must involve coherent transitions of one sort or another, as there is no possibility for any other approach.
This motivates our consideration of what kind of models and what kind of physics to focus on in many-site models derived from the Lattice Resonating Group Method. Our discussion of many-site models above was based on the use of a Dicke algebra, as this is familiar in the modeling of coherent effects associated with two-level systems. However, in addressing the problem of transitions of deuterons from molecular states to compact states, an underlying two-level model is not going to do the job. Instead, we require more sophisticated models based on the three-level generalization of the Dicke algebra. The mathematics associated with this generalization has recently been considered as part of an ongoing PhD thesis research effort of I. Chaudhary at MIT, and it has been verified that the generalization of the Dicke states in this case (which are the states of highest symmetry) leads to many-particle matrix elements that are identical to those in the Dicke algebra for equivalent definitions of upper and lower state occupation. It is expected that this will be a result available in the literature, but as yet no reference has been identified.
This implies that we are able to apply our analytical skills and our intuition to more sophisticated many-site models, and begin to understand their properties. The simplest model of this class is one in which we assume an initial population of deuterons in molecular states, an initial population of helium atoms, and no initial occupation of compact states. The simplest possible model of this kind will assume only a single molecular state, a single compact state, and a single helium final state in association with each site, and uniform interaction with the highly excited phonon mode. The Hamiltonian for this kind of model in the absence of loss terms can be written as
In this model, there are three states with energies EHe (ground state helium), Ecom (compact state), and Emol (molecular state). The highly excited phonon mode is taken as before to be a simple harmonic oscillator. Transitions from molecular states to the compact states are modeled with an interaction inhibited by the tunneling factor e−G, but otherwise involve phonon exchange according to the phonon interaction models discussed above. Transitions between the compact states and the helium states are modeled as we did previously.
This model implements a coupling scheme that would result from preferential phonon exchange in the case of compact states involving a free neutron, and is consistent with our best understanding at the momentum of the phonon exchange mechanism under discussion.
As written, the Hamiltonian for the three-level model is unlikely to lead to much of interest, since there is a very high degree of symmetry present in the coupling between the different states associated with the three-dimensional configuration space when the number of sites, nuclei and phonons is large. This is the same conclusion that we reached in the case of the Dicke model discussed previously.
Based on our experience with the many-site two-level model, we know that we need to include loss in order to arrange for useful exchange of phononic and nuclear energy. As the new three-level model is the same for these interactions we expect the behavior of the model to be the same as well. The decay terms will be very fast for states that have less energy than the relevant eigenvalue energy, which means that the loss will be very nonlinear in the associated Dicke number between the helium states and the compact states. This breaks the symmetry, and we will see probability distributions that are extended in n and M12 (the Dicke number associated with the helium and compact state levels) when the phonon exchange is large enough to stabilize the compact states, and when the number of compact states and helium states are on the order of 10 or greater within a phonon coherence domain.
The dynamics of this more sophisticated model in this regard are reasonably clear. When molecular states make transitions to compact states within the model, the compact states will be able to rapidly convert nuclear energy to phononic energy, corresponding to a rather efficient conversion process. As described above, the difficulty is in arranging for these transitions in the first place, since the tunneling factor inhibits such transitions.
Another effect is present in this model that we did not pay attention to in our previous discussion. The coupling between the molecular states and the compact states within this model now has a Dicke enhancement factor present if there is both occupation of the molecular states as well as occupation of the compact states. Consequently, the occupation of the compact states is important before the first molecular state to compact state transition occurs.
The implication of this is that the coupling of the molecular states within the model to the compact states depends on the occupation of the compact states. Hence a model with zero initial occupation of compact states will have a slow initial transfer of population from the molecular states to the compact states. However, the model will show a rapid initial establishment of population due to transitions involving helium, as the helium to compact state transitions are very fast. Hence the presence of helium initially is predicted to draw population from the molecular states by establishing compact state occupation.
This feature of the model is ultimately at the heart of our requirement for the initial presence of 4He in the metal deuteride (or equivalently, 3He in the mixed metal deuteride and hydride).
There is of course an alternate coupling possible from the model outlined above. We could have specified instead transitions between the molecular state and the helium state, leading to a model Hamiltonian of the form
In this model, Dicke enhancement factors would be present initially due to the presence of both molecular state deuterium and ground state helium. More complicated models including both kinds of transitions are possible, and further research will clarify which are most relevant to experiment.
We note that the use of initial helium seeding of the metal deuteride is beneficial in all of the different models of this class. We note that occurrence of Dicke factors within these models requires phase coherence. While the fast transitions between the helium and compact states will help in this regard, we will not have uniform phase in the molecular state occupation. Hence the Dicke factors will be less than what one might hope for based on state occupation alone. This problem has not yet been analyzed.
We can begin to contemplate the development of reaction rate estimates from these models. The intuition is that the fast transitions between the helium states and the compact states will rapidly establish a distributed probability distribution in phonon number and the Dicke number associated with these states. We can think of this as a “stiff” distribution in two of the three dimensions that is “pushed” by the sharp nonlinearity of the loss terms. Consequently, the rate limiting effects associated with the dynamics of the probability distribution are those associated with transitions in the third dimension—specifically, those associated with the transitions from the molecular states to the compact states (or equivalently, to the helium states depending on which model is adopted). The matrix elements associated with these transitions in the model are
Unn′e−G˜NDickeUoe−G
where the Dicke factor NDicke is on the order of the square root of the produce of the number of compact states present and the number of in-phase molecular state deuterons present within the coherence domain of the highly excited phonon mode.
The dynamics associated with this coupling is determined by the associated dephasing of the quantum states of the system. If the rate of dephasing of these states is faster than the frequency determined by the coupling matrix element divided by , then the rate will be determined by the Golden Rule, which basically means that no observable transitions will occur. If the dephasing is on the order of or slower than this rate, then the transitions will proceed at the rate associated with the spread of probability amplitude in the associated configuration space, which is on the order of
Γ˜NDickeUoe−G
For the molecular problem, we would estimate
Uoe−G˜10−32 eV
and possibly a larger number for PdD based on the low-energy dd-fusion cross section measurements. This corresponds to on the order of on the order of 1-103 reactions per second per cubic centimeter for a Dicke factor of unity, depending on how large the molecular state fraction is assumed to be. A Dicke factor in the range of 108-1012 is thought to be well within the range of what is possible from these kinds of models, leading to total reaction rate estimates in line with observations. We note that the occurrence of large Dicke factors would be associated with random bursts of anomalous products, in qualitative agreement with the large majority of observations. We note that variations in levels of products have been observed at the level of roughly three orders of magnitude in the case of heat production (limited by detector capabilities), and on the order of six orders of magnitude in association with tritium and fast particle production. If we interpret these observations in terms of Dicke bursts, the associated Dicke numbers seen to date are as large as 106, consistent with models of the type described here.
The basic conjecture here is that if we assume that the models under discussion work largely in the coherent limit as described here, then the quantitative results of the models appear to be qualitatively in agreement with a great many observations of anomalies in metal deuterides. If the relevant dephasing is fast and Golden Rule rates apply, then this model gives rates that are sufficiently slow as to be unobservable. We have devoted some work to the problem of dephasing in this quantum system. The basic observation is that the compact states are pretty tough to interact with (especially the spin zero states, which do not even have a magnetic interaction) other than through the couplings described here which are very fast. Once a coherence has been established, it seems that there are good reasons that it might be maintained, even with the destruction of individual molecular states and even with diffusion effects included. The basic argument is that on average, there remains very nearly the same total number of molecular state deuterons in a mesoscopic or macroscopic volume of metal deuteride. Moreover, if phase interruptions occur, there are on average always a similar number of other molecular state species that have the requisite phase relation with the compact states and helium states, since we assume that only a subset of the molecular states are involved at any given time. Future work will shed light on this conjecture.
The premise of the initial formulation, which posits that nuclear reactions in a lattice should include the lattice at the outset, is a very solid physical statement. Over the years, we have attempted to study systematically the models that arise as a consequence of this initial physical statement. In the course of the work, we have been able to explore many aspects of the models, and to understand aspects of many of the physics issues that the new models raise. We have found that many features of a great many experiments can be understood in terms of the model, and that there has begun to be established a predictive capability in association with the model. The model has only improved over the last five years with each improvement of the associated physics, modeling or sophistication. This was not true of a very large number of previous models, and this has convinced us that much of it is correct in detail. As we have outlined, there are uncertainties within the different parts of the model that we expect to be resolved in time.
Nevertheless, the predictions of the model as to what is required for the development of excess heat in metal deuterides and in mixed metal deuterides and hydrides is pretty clear. Molecular state D2 within the metal lattice is required (or HD in the case of the p+d reactions), the more the better. Strong excitation of at least one phonon mode that produces motion of interstitial helium at the level of on the order of 100 fm or greater appears to follow from the phonon exchange calculations in order to produce stable compact states. Helium is required in order to increase the reaction rate (4He for the d+d reactions and 3He for the p+d reactions). There needs to be on the order of at least 10 compact state and helium species present within a phonon coherence domain in order to exchange energy efficiently between the nuclear and phononic degrees of freedom. Devices that satisfy these constraints are predicted within this model to produce energy. The inventions described in this patent then follow from the requirements of the model, and in large part are supported by a wide range of experimental observations that pertain to one piece or another of the physics under consideration.
The accompanying figures best illustrate the details of the apparatus, system, and method for implementing the present invention. Like reference numbers and designations in these figures refer to like elements.
In an embodiment the above process is implemented to create a vacancy-enhanced metal lattice structure. More specifically, there is an introduction of hydrogen. Metal hydrides have long been sought as vehicles to contain hydrogen for storage and shipment. The advantages of storing hydrogen in a metal lattice rather than using high pressures and or low temperatures to compress (in the limit, to liquefy) hydrogen gas are: improved volumetric storage efficiency, increased safety, potentially lower costs, the convenience of working with small or intermediate sized devices. Metal hydrides also are sources of intrinsically pure hydrogen and in many applications gas stored in this way can be used without further purification.
High purity hydrogen is increasingly being used in a range of chemical processes from semiconductor fabrication to the preparation of fine metal powders. Increasing attention also is being focused on hydrogen fuel cells and hydrogen internal combustion engines as means to reduce the rate of carbon dioxide emission accompanying power generation both stationary electrical and motive. Both technologies (fuel cell and hydrogen internal combustion) are undergoing rapid development to meet this need. Both developments are far in advance of what is needed for concomitant hydrogen storage.
Recognizing this need, various industries and governmental agencies are working rapidly to: identify a pathway to establish an industrial hydrogen infrastructure; establish scientific programs to develop new materials and means for hydrogen storage; develop a hydrogen feedstock strategy.
A great deal of effort has been devoted to the production of suitable metallic alloys for the storage of hydrogen. These systems are usually relatively expensive multi-component alloys. In addition to the issue of cost, these alloys have relatively low gravimetric storage capacities, typically 1-2 wt. %, and suffer mechanical damage on repeated cycling, which destroys the system integrity. More recently, the hydrogen storage properties of a number of carbon materials have been investigated. Although impressive storage capacities have been claimed in some cases, these values were obtained only at high pressure (in excess of 100 atm.). In addition, elevated temperatures are required for hydrogen desorption.
In selecting a material suitable for hydrogen storage several issues are paramount: high volumetric and/or gravimetric hydrogen storage ability (capacity); the facility to store and release hydrogen at rates compatible with or in excess of the demand cycle (dynamics); the ability to withstand large numbers of cycles and high rates of cycling without important degradation of material (durability); the ability to absorb and release hydrogen on demand, with relatively small changes in temperature and/or pressure conditions in the vicinity of the desired operation point; low cost; low toxicity; intrinsically high safety margins.
These constraints effectively rule out all known metals and alloys in the phases in which they normally are found. An alternative approach is suggested from the work of Fukai in which extremely high pressures and temperatures were used to produce a high vacancy phase of Mo, Ni, Pd and other fcc (face centered cubic) metals, in which the vacancies were stabilized by the presence of absorbed hydrogen at very high chemical potential. The experiment conducted by Fukai as noted above is incorporated herein by reference. Fukai Y. and N. Okama, Formation of superabundant vacancies in Pd hydride under high pressures. Phys. Rev. Lett., 1994, Vol. 73, p. 1640.
The important properties of the “Fukai” phase are:
These advantages make possible the conversion of relatively cheap, safe, non-toxic metals (such as Ni) that are kinetically poor hydrogen storage materials in their normal phase, into highly dynamic, high efficiency hydrogen storage materials. However, the means employed by Fukai to accomplish this end is not practical in commercial application since it requires the use of high temperatures for periods extended sufficiently for metal vacancy diffusion (many hours or days) at pressures of hydrogen attainable only at two or three highly specialized facilities in the world.
This embodiment of the invention can be used to produce a vacancy-stabilized metal hydride phase suitable for use as a hydrogen storage element
This method works for both hydrogen and deuterium. For chemical energy applications hydrogen would be preferred; for nuclear energy applications deuterium or a mixture of deuterium and hydrogen would be preferred. Electron beam irradiation of metals leads to the formation of vacancies as lattice metal atoms are imparted energy and momentum to move from their normally ordered sites. In the absence of hydrogen the limiting concentration of vacancies formed this way is only on the order of 0.1% to 0.2% as such vacancies tend to “heal” from a state of high lattice energy. In the absence of vacancies, however, hydrogen has little mobility in most metal lattices. Noted exceptions are Fe and Pd at room temperature, and Nb, Ta, V, etc. at temperatures in excess of 200° 0C. For these metals, in the regimes of temperature specified, direct formation of vacancy enhanced, high hydrogen phases can be achieved by pre-loading the metals with hydrogen and then subsequent electron beam irradiation. In general it is necessary to treat metals alternately or simultaneously to hydrogen and electron beam exposures in order to produce significant volumes of vacancy enhanced high hydrogen storage metals.
The temperature and pressure of hydrogen treatments must be calculated metal-by-metal from the known coefficients of hydrogen diffusion in these metals. Electron beam irradiation at relatively high flux is required for periods of minutes or hours in initial materials treatment to produce the desired phase. The irradiation dosage should be of order 1017/cm2 or higher, using electron energies in the range 0.1-5 MeV. Higher energies should be avoided so as not to induce radioactivity in the metal. A concentration of 0.25% up to 25% of vacancies in a host lattice structure can be achieved.
Vacancy stabilized enhanced hydrogen storage materials can be used with advantage over existing metal, carbon and compressed hydrogen storage methods in all applications where hydrogen presently is used or produced:
There are also several important points that should be noted with regard to the advantages of this embodiment of the present invention:
The methods of fabrication are the same as can be used to form the heat producing elements in the nuclear applications, without the need for: helium seeding, surface sealing, phonon stimulation. Also, H2 can be used instead of D2.
In another embodiment of the present invention, adding helium to a vacancy enhanced hydrogen and/or deuterium storage material produces another novel material with additional utility. More specifically, a helium-seeded, vacancy enhanced, hydrogen and/or deuterium loaded lattice is critical to the embodiment of the energy release method described in the patent.
Helium can be introduced into the lattice before, after or during the hydrogen loading and vacancy creation steps, but practical considerations suggest that it is easiest and most effective to load helium into the lattice before hydrogen loading and vacancy creation. Helium can be loaded into the lattice via several methods, including:
Given that there is 5.5 ppm (parts per million) helium in the atmosphere, an atomic density of 10−10 to 10−8 helium atoms occur naturally in most metals. When most metals are made the concentration of helium is not controlled and will exist in trace amounts. Thus, the advantage of the present invention is that the helium concentration in the host lattice structure is controlled. The result is material that has an atomic density of helium of 10−7 or higher; but preferably on the order of 10−5. (To be clear, an atomic density of 10−5 means that there is 1 helium atom for every 100,000 atoms of the host lattice)
a-17e illustrates energy being created in a metal deuteride in accordance with an embodiment of the present invention. In
It is contemplated by the invention that the host metal structure includes the use of metals such as, but not limited to, Pd, Ni, Pt, Rh, Ru, Ti, Nb, V, Ta, W, Hf, Zr, Mo, U, Sc, Mn, Co, Zn, Y, Zr, Cd, Ag, Sn and other alloy and composite materials.
By way of example if Pd is used, the Pd is of high purity (but not the highest) in the range of 99.5%-99.9% with a diameter of 50-125 μm and a length of 3-30 cm.
Helium-4 (4He) is introduced into the Pd lattice to atomic ratio one part in 105. The levels of 4He normally found in Pd are approximately 1010 atoms per cm3 (˜1 atom in 1013 or 8 orders of magnitude less than the preferred value). Examples of obtaining the desired concentration of 4He into the Pd contemplated by the invention are as follows:
1) High temperature diffusion—
2) Helium ion implantation—A known quantity of 4He atoms can be implanted at known depth below the Pd surface by varying the ion current, time and energy of an ionized helium beam.
The average loading of deuterium in Pd is ≧0.85.
1) Using electrolysis at near ambient temperatures in an electrolyte that includes the use of strontium sulfate (SrSO4) dissolved in high purity D2O (resistivity >10 MΩ cm) to concentration 10−5 M. It may be necessary to vary the cathodic current density in the range 10≦i≦250 mA cm−2 in order to achieve a maximum D/Pd loading determined as a minimum in the resistance of the PdD structure measured in the axial direction; and
2) The use of deuterated alcohol is substituted for D2O in procedure 1. Alcohol electrolytes offer two advantages: a) they are more easily purified (e.g. by distillation) and contain lower concentrations of cations deleterious to loading; and b) because of their lower freezing point, electrolysis temperatures can be reduced which thermodynamically favors attainment of the high loading state. At lower temperatures and substantially lower electrolyte conductivities, the kinetic of the loading process and accessible range of cathodic current densities, are much less in alcohol electrolytes than in aqueous. As for “1, however, current densities must be adjusted while monitoring the loading in order to achieve the maximum loading state.
To attain the needed high chemical potential of deuterium it is necessary to take more than usual care in the avoidance of impurities derived from the electrolyte, the anode, the cell walls, or the ancillary hardware used in the electrochemical loading process. Materials found suitable and compatible with the attainment of needed levels of loading are Pt, Teflon®, quartz, Pyrex® and the like. Each of these materials must be scrupulously cleaned before use. Because avoidance of impurities cannot be assured, the electrolyte purity inevitably degrades with time of electrolysis. Loading is thus constrained by two opposite rate processes: 1) radial diffusion of D atoms into the Pd lattice from a state of high electrochemical potential at the electrochemically active surface; 2) and contamination of that surface by discharge of species dissolved or suspended in the electrolyte. As an important consequence, the condition of maximum loading is transient. Thus, it is contemplated by the invention that there is monitoring of the D/Pd loading in order to judge the appropriate transition time between this process step, and the next. An example of monitoring the loading is by using four terminal resistance measurement.
Contamination of the Pd surface that is deleterious to loading also is inevitable during fabrication, shipping, pretreatment and mounting in the electrochemical cell. Contamination is eliminated before undertaking the electrochemical loading by surface cleaning and pretreatment. An example of decontaminating the Pd surface is passing current at high current density axially along the wire. The current density should be calculated or adjusted to be sufficient to raise the temperature of the Pd wire to dull red heat (600-800° C.). Only a few seconds of this treatment and no repetition are necessary to completely remove deleterious species from the Pd electro-active surface and effect a favorable recrystallization of the bulk.
It is contemplated by the invention that immediately upon attainment of the desired maximum loading condition, the system must be stabilized by blocking egress of D atoms from the PdD surface. Examples of methods of sealing the PdD surface contemplated by the invention are as follows:
It is also contemplated by the invention that the number of vacancies available in the metal host can be enhanced. For example, enhancing the vacancies in a PdD host metal can be accomplished by subjecting the metal to radiation damage thus imparting kinetic energy and motion to lattice Pd atoms. In principle, any radiation of sufficient intensity may be used for this purpose, for example, an electron beam irradiation. In order to preserve the deuterium atomic loading during shipment and while samples undergo electron beam irradiation loaded wires should be maintained at liquid nitrogen temperatures (77K) or below.
In
The phonon field is applied to the host lattice 31 by use of a stimulation source. The host lattice structure 31 can be stimulated to demonstrate effects of heat generation via nuclear reaction (D+D) and production of helium (4He). Stimulation involves exciting appropriate modes of lattice phonon vibrations. A number of methods are available to provide such stimulation to the host lattice structure. For example, stimulation to the host lattice structure can be achieved by fluxing of lattice deuterium atoms across steep gradients of chemical potential (the electrochemical mode); fluxing of electrons at high current density (the “Coehn” effect); intense acoustic stimulation (“sono-fusion”); lattice fracture (“fracto-fusion”); or superficial laser stimulation (“laser-fusion”). It is contemplated by the invention that the stimulation of the host lattice structure can also be effectively stimulated by the following: 1) surface stimulation with a red laser diode in the range of wavelength with surface power intensity >3 W cm−2; 2) beating laser; 3) surface stimulation with lasers in the Terahertz frequency range; 4) axial current stimulation using both direct and alternating currents (dc and ac) and current pulses, at current densities greater than 105 A cm−2.
In
In
e illustrates that after many oscillations of the process discussed above in
The demonstration of the effect is a measurement of a temperature rise in the prepared metal host. For example a measurement of the temperature rise in a Pd metal host structure. Such measurements can be made in a number of ways, either calorimetrically (measuring the system total heat flux) or simply by monitoring the local temperature rise. Although demonstration of the effect is more easily made by observing a local temperature rise in response to the stimulus, other examples of demonstrating the effect of the energy process contemplated by the invention are as follows:
After demonstration of the heat effect wire samples should be removed, sectioned, and subjected to analysis for 3He and 4He in the metal phase. A high sensitivity and high resolution mass spectrometer can be used for this purpose. Any indication that 4He levels have increased or that the 3He/4He ratio has changed from it's natural value can be used to demonstrate that a nuclear process has occurred in the lattice.
The following is an example of an experiment used to confirm the effectiveness of the reaction process noted above. Project Cobalt Experiment 3A was done to execute an experimental program designed around the “best practices” of making and using the invention. Project Cobalt determined that the ideal program would involve the optimization of multiple parameters as given below:
The conclusions of the results were that the experiment with Pd yielded between 50 mW and 240 mW of excess power starting on day 4 (Nov. 29, 2002) and continuing through day 9 (Dec. 4, 2002) in correlation with the metal co-deposition and laser stimulation. Given that the volume of the cathode was 0.00875 cc, the maximum power density was approximately 28 W/cc. This output compares favorably with uranium fission, which produces approximately 50 W/cc. The total amount of excess energy produced, calculated by integrating the instantaneous excess power, yielded 7 Wh. The experiment was terminated when the electrical characteristics of the cell exceeded an arbitrarily determined control threshold.
a-19e illustrate another reaction processes in accordance with the present invention. The reaction process in
Further Exemplary Embodiments with Materials Comprising Molecular Deuterium and Molecular Hydrogen-Deuterium
As explained elsewhere herein, increasing the amount of molecular deuterium (referred to herein as “D2”) or molecular hydrogen-deuterium (referred to herein as “HD”) in host materials can be beneficial for promoting nuclear reactions within the host. For example, if two deuterons are to interact, such as described elsewhere herein, the interaction probability can be higher when the deuterons are in a molecular D2 state as compared to when they occupy neighboring sites in a metal deuteride. Similarly, if hydrogen and deuterium are to interact, such as described elsewhere herein, the interaction probability can be higher when the hydrogen and deuterium are in a molecular HD state. Further exemplary embodiments utilizing materials that facilitate the presence of D2 and HD will now be described.
According to an exemplary embodiment, an apparatus 200 shown in block diagram form in
The excitation source 204 can be, for example, an electromagnetic-radiation source for irradiating with electromagnetic radiation (e.g., a laser source or other optical source), a transducer (e.g., a piezoelectric device or quartz crystal with suitable electrodes such that application of an appropriate current causes a mechanical displacement such as vibrational motion, or any suitable transducer not limited to electrically driven transducers that can impart mechanical displacement to the material), an electrical power source (e.g., DC or AC source for applying electrical current to the material), a particle source (e.g., for irradiating the material with particles such as electrons or ions), or a heater (e.g., a resistive heater or a radiative heater), or any other suitable excitation source for supplying energy to the material such as described elsewhere herein. Combinations of the excitation sources such as those described above, can also be used. It can also be beneficial to apply such stimulation in a modulated fashion (e.g., periodic or non-periodic dynamic fashion) as it is believed that modulations of such stimulation can facilitate coupling to acoustic phonons in the material 202, thereby facilitating generation of the nuclear reactions. For example, periodic modulations can be on the order of the range of frequencies of such acoustic phonons. As with other embodiments disclosed herein, stimulation can also occur by the fluxing of hydrogen or deuterium atoms or molecules across a concentration gradient. A concentration gradient can be established, for example, by suitably controlling the chemical environment of the material 202.
The load 206 can be, for example, a heat exchanger, e.g., one or more cells such as cells 83 which transfer heat to a heat transfer fluids as shown in the electrochemical cell example of
While the excitation source 204 and the load 206 are shown as separate features in the block diagram, it should be understood that those features can share a common device or devices in some instances, e.g., both devices can share the same transducer that generates vibrational motion from applied electrical energy and that generates output energy from vibrational motion generated by reactions, in some examples. In such examples, including those described further below in connection with
In one aspect the material 202 can comprise an isotopic variant of a dihydrogen transition metal complex with a substitution by at least one of D2 and HD (the presence of HD relates to the case of the proton-deuteron pathway as described elsewhere herein). Measurements by researchers indicate that the separations between protons in H2 present in transition-metal complexes are close to the separation between protons in free H2 (e.g., as reported in G. J. Kubas, Metal Dihydrogen and σ-Bond Complexes). Similarly, the separations between deuterons in D2 present in such transitional metal compounds are expected to be close to the separation between deuterons in free D2 (the same is expected to be true in the case of HD). Thus, the interaction probability between two deuterons, or between hydrogen and deuterium, is expected to be significant in these materials.
Exemplary materials in this regard include (using the short hand chemical notation conventional for such materials as used in G. J. Kubas, Metal Dihydrogen and σ-Bond Complexes) W(D2)(CO)3(PH3)2, Cr(CO)3(P/Pr3)2(D2), Mo(CO)(dppe)2(D2), W(CO)3(P/Pr3)2(D2), FeH(D2)(PEtph2)3, [RuH(H2)(dppe)2]+, Cr(CO)3P2(D2), Mo(CO)3P2(D2), trans-[Mo(CO)2(PCy3)2D2] and trans-[W(CO)2(PCy3)2D2], as well as corresponding materials in this list wherein “HD” is substituted for “D2”, as well as complexes that contain both D2 and HD. Such materials can be fabricated by methods known in the art for fabricating dihydrogen transition-metal complexes, such as disclosed, for example, in Chapter Three (“Synthesis and General Properties of Dihydrogen Complexes”) of G. J. Kubas, Metal Dihydrogen and σ-Bond Complexes, with appropriate processing in the presence of D2 and HD gas, as discussed below.
For example, it is known that a commercially available zero valence Mo compound, Mo(CO)3(C7H8), where (C7H8)=cycloheptatriene, can be reacted with 2PCy3 (where Cy=cyclohexyl) in benzene or toluene under a hydrogen atmosphere to produce trans-[Mo(CO)2(PCy3)2H2], which precipitates out as yellow microcrystals with a yield of 60-70%, within 2-3 hours. In this compound, H2 is readily lost at room temperature, and the material must be stored under a hydrogen atmosphere. Similarly, it is believed that trans-[Mo(CO)2(PCy3)2D2] can be prepared in similar manner wherein the reaction is carried out in D2 gas instead of H2 gas.
As another example, it is known that a commercially available compound, W(CO)3(C7H8) (where (C7H8)=cycloheptatriene) can be reacted with 2PCy3 in benzene or toluene in a hydrogen atmosphere to make trans-[W(CO)2(PCy3)2H2], which precipitates out also as yellow microcrystals. This compound is reported as being more stable than the above-described molybdenum compound, but its stability may be enhanced by storing it in a hydrogen atmosphere. Similarly, it is believed that trans-[W(CO)2(PCy3)2D2] can be prepared in similar manner wherein the reaction is carried out in D2 gas instead of H2 gas. In a paper by G. J. Kubas et al., J. Am. Chem. Soc., 106, 451 (1984), the authors reported a yield of 85-95% for this synthesis in 1 atmosphere H2, and further reported observations of spectra from complexes with isotopic substitutions of D2 and HD for H2.
Thus, in general, it is believed that synthesis approaches of basic metal dihydrogen metal complexes can be modified by using D2 and HD gas atmospheres in place of solely H2 atmospheres to thereby generate suitable dihydrogen transition metal complexes with a substitution by D2 and/or HD. Such materials can be stable at room temperature. In this regard, those of ordinary skill in the art will understand that a reference to D2 and HD gas refers to a mixture of D2, HD, and H2 gases considering the dynamic transformations that normally occur between these forms.
It will be appreciated that preparations of such materials can be facilitated by adjusting (e.g., increasing) the temperature during processing to facilitate the reactions. Also, such materials can be prepared by starting with dihydrogen transition metal complexes at the outset and then heating these at elevated temperature and pressure in D2 gas, wherein substitutions of H2 in the complexes by D2 and HD can occur.
In another aspect, the material 202 can comprise a fullerene-based material. A fullerene-based material as referred to herein includes a material comprising any of various cage-like, hollow molecules that include hexagonal and pentagonal groups of atoms including, e.g., those formed from carbon, and which may include additional species of atoms as part of the cage structures, within the cage structures, or between the cage structures of adjacent molecules. Also included within the scope of such materials are those that also include atomic arrangements other than hexagonal and pentagonal groups. Non-limiting examples include Buckyballs (e.g., C60 or similar molecules with a different number of atoms), carbon nanotubes (either closed-ended or open-ended), and the like. Other non-limiting examples included with the scope of fullerene-based materials include the above-described materials in solution, incorporated into a solid such as a polymer matrix or incorporated into a solid formed of a compacted mixture of fullerene powder with another suitable powder, which can act as a binder. As discussed below, fullerene materials can be processed to incorporate D2 and/or HD prior to incorporation in a solid or a liquid. The loading with D2 and/or HD can be enhanced with appropriate sealing of the material such as described elsewhere herein (such sealing is generally applicable to the materials disclosed herein) and/or by maintaining such materials in an atmosphere of D2 and HD.
Encapsulation of H2 and inert gases in fullerenes is known in the art. For example, rare gases have been encapsulated in fullerenes at low yield by heating the fullerenes in the rare gas atmosphere, such as described in R. J. Cross and M. Sanders, Fullerenes—Fullerenes for the New Millennium, Electrochemical Society Proceedings, Volume 2001-11, 298. Rare gases have been encapsulated in fullerenes by acceleration of rare gas atoms into stationary fullerenes. In the latter case, the atom could slip through the cage with sufficient noble gas atom velocity, and be encapsulated with significantly higher yield. The encapsulation of 3He and 4He has been reported through this method. Methods to purify fullerenes with encapsulated atoms are discussed, for example, in Chapter 12, “Encapsulation of an atom into C60 cage,” by Y. Kubozono, in Endofullerenes, A New Family of Carbon Clusters, edited by T. Akasaka and S. Nagase, Kluwer Academic Publishers, Dordrecht (2002).
More recently, molecular hydrogen has been inserted into an open-cage fullerene derivative as reported by Y. Murata et al., J. Am. Chem. Soc. 125, p. 7152 (2003), which also reported gas phase generation of H2 in C60. Synthesis of an open-cage C60 structure (a C60 molecule with an opening therein which facilitates insertion of other species into the molecule) is discussed in G. Schick et al., Angew. Chem., International Edition, 38, 2360 (1999). Briefly, the open cage structure was synthesized by reacting C60 with diazidobutadiene at 55 degrees C. for four days. Murata et al. reported the insertion of H2 into such an open-cage structure by exposing a powder made of the open-cage fullerene to 800 atmospheres of H2 at 200 degrees C. in an autoclave for 8 hours, at also at lower pressures of 560 atmospheres, and 180 atmospheres with lower yields. No loss of H2 from the open-cage structure in a solution was observed at room temperature over 3 months, and the observation of H2 release was observed at 160 C and above.
In a similar manner, it is believed that D2 and/or HD can be inserted into an open-cage fullerene structure by preparing an open-cage fullerene as discussed above and by heating such a powder at elevated pressure in an autoclave in the presence of D2 and HD gas. Further, as noted in Murata et al. referred to above, the open cage structure can then be closed to provide closed encapsulation of the inserted species by using laser irradiation. Moreover, such a powder could also be processed as described above to include small amounts of 4He and/or 3He or in order to reduce the time to achieve a significant nuclear reaction rate (the utility of including 4He or 3He in conjunction with D2 or HD to facilitate nuclear reactions is described elsewhere herein). Alternatively, a small amount of fullerene powder containing fullerenes that have been inserted with 4He and/or 3He could be mixed with a fullerene powder that has been inserted with D2 and/or HD, and the resulting mixture could be utilized in a solid or liquid material containing such fullerenes.
Also, for example, fullerenes have been made into solid structures through a variety of methods, such as described in Chapter 14, “Structures of Fullerene-Based Solids,” by K. Prassides and S. Margadonna, in Fullerenes: Chemistry, Physics, and Technology, edited by K. M. Kadish and R. S. Ruoff, Wiley-Interscience, NY (2000). Crystalline powders of C60 have been found by others based on x-ray diffraction to form random collections of hcp and fcc lattice structures formed of nearly spherical fullerenes with interstitial spaces. Thus, previously encapsulated fullerenes having D2 and/or HD inserted therein prepared such as described above can be formed into fullerides and other fullerene-based solid materials for use as the material 202 shown in
In another aspect, the material 202 can comprise a semiconductor material or an insulator. The use of hydrogen as a passivating material in semiconductors, such as silicon and GaAs, for example, is well known. Theoretical studies indicate that hydrogen in GaAs should form molecular H2 in tetrahedral sites, which are deep wells for the molecular state (L. Pavesi et al., Phys. Rev. B 46, 4621 (1992)), and that hydrogen in silicon should form molecular H2 in Si (P. Deak, et al., Phys. Rev. B 37, 6887 (1988); and C. G. Van de Walle, et al., Phys. Rev. B 39, 10791 (1989)). It is believed that such semiconductor materials (e.g., Si and GaAs) can also be produced with D2 and/or HD therein by heating such material in the presence of D2 and HD gas at elevated temperature and pressure, which would be useful as material 202. Also, it is believed that insulators (e.g., such as NaCi, CaF2, CaO, MgF2, and MgO and other ionic crystals) can be prepared with deuterium therein (as well as with He-3 and/or He-4) by heating those materials in the presence of elevated pressures of D2 and HD gas in an autoclave as described elsewhere herein.
In another aspect, the material comprising D2 and/or HD can comprise a liquid.
The apparatus 300 can be operated in a manner such as already described above. In particular, a transducer can be initially powered with electrical energy to apply vibrational energy to the material 302 to initiate the nuclear reactions (through phonon coupling to the reactions). Upon initiation of the reactions, the electrical power to the transducer can be turned off, and the transducer can then operate to generate electrical energy from vibrational motion of the material 302 coupled into the transducer 304, wherein the vibrational motion of the material 302 is generated from the nuclear reactions occurring therein. This electrical energy can then be drawn off the electrodes 314 for use in a suitable electrical load as desired. In this aspect, it will be appreciated that the D2 and/or HD resides in a condensed matter environment that supports acoustic modes, or more generally acceleration, in which a highly excited system can interact with nuclei. Such modes can include, for example, a highly excited acoustic mode, a hybrid acoustic and electrical oscillation mode associated with the combination of an oscillator circuit coupled to transducer 304 (e.g., piezoelectric material) and material 302, or a rotational mode.
While the transducer 304 carries out dual roles in this example (i.e., stimulating the material 302 initially and serving as a load/converter for withdrawing/generating useful electrical energy), it should be understood that a separate excitation source such as described in connection with
In connection with this embodiment, it will be appreciated that molecular hydrogen gas is known to go into many liquids with a significant solubility, and the same is expected for D2 and/or HD. As noted above, D2 and/or HD can be driven into the liquid 302 by the pressure of the D2 and HD gas above the liquid 302. Another approach is to generate the gas, if desired, through electrolysis of species in the liquid and maintain by adjusting the gas pressure to desired levels. Yet another approach is to generate the gas by chemical reactions within the liquid.
In another aspect, the material 202 can comprise at least one of D2 in condensed form and HD in condensed form at low temperature. In this regard, “D2 in condensed form” (for example) as used herein refers to D2 that has been condensed to form a solid or liquid itself, either with or without being combined in a mixture with another species, and similarly for HD. For example, such material could be substantially uniform liquid or solid D2, substantially uniform liquid or solid HD, a mixture of the same, or any of these possibilities in a mixture with another condensable species such as argon. It is contemplated that that the amount of condensed D2 and/or HD could be one-half or more of the total mixture by weight in such a mixture. Low temperature in this regard refers to a temperature sufficiently low that such condensation can occur. Those of ordinary skill will appreciate that molecular hydrogen condenses into a liquid at approximately −259 degrees C. at standard pressure and solidifies at approximately −262 degrees C. at standard pressure, and that D2 and/or HD will similarly condense in approximately the same temperature regime. Thus, this example is primarily applicable to embodiments such as direct coupling of vibrational motion into electrical energy (e.g., electricity) rather than to embodiments for generating heat. In such an example, the apparatus 200, or at least a portion containing the material 202 can be suitably insulated and cooled using conventional approaches (e.g., helium refrigeration of a support member arranged in a vacuum environment provided by a suitable vacuum chamber).
In connection with this embodiment, it will be noted, for example, that argon saturated with hydrogen can be cooled slowly to produce solidified material containing molecular hydrogen (see, e.g., Kriegler et al., Can. J. Phys. 46, 1181 (1968)). It is believed that such mixtures of inert gases with D2 and/or HD can similarly be condensed and utilized as described above.
As described elsewhere herein, the reactions can comprise at least one of transformations between D2 and He-4 and transformations between HD and He-3.
As will be apparent from the discussion above, one way of generating electricity from nuclear reactions in materials is to convert excess heat to electricity using thermoelectric converters, Stirling engines, or other types of engines. Such scenarios contemplate a technology in which heat is produced at elevated temperatures, perhaps between 250 C and 1000 C, and then converted to electricity by whichever conversion technology is most convenient or cost efficient. The requirement for an energy conversion step after the initial energy production can be significant, in the sense that the resulting technology may be complicated, and losses are expected. For example, in the case of electricity production, the efficiency of small scale solid state thermal to electric converters is not high, and unused heat must be dissipated. In what follows, further embodiments for the direct conversion of vibrational motion generated by nuclear reactions in materials to electrical energy are described, which build upon the discussion presented in connection with
As described herein phonon exchange can occur in association with a nuclear reaction process. It follows directly that when two or more phonons are exchanged in reactions at different sites with a common phonon mode, they can be coupled quantum mechanically, and proceed as a second-order or higher-order process. In this framework, the energy from the nuclear reactions appears initially in the highly excited phonon mode, with the possibility of excitation of other thermal modes as well. Excess heat comes about in this picture in association with loss mechanisms of the highly excited phonon mode. In other words, energy from reactions is expected to be coupled into highly excited phonon modes primarily, and the degradation of the highly-excited mode energy into thermal energy is a subsequent effect.
According to one embodiment, an apparatus 400 can be configured as shown in the block diagram of
The apparatus also comprises an excitation source arranged to stimulate the material 402 to generate reactions in the material 402, wherein the reactions generate vibrational motion of the material 402. In the example of
Operation of the apparatus involves stimulating the material 402 as discussed above to cause nuclear reactions in the material 402, wherein the reactions generate vibrational motion of the material 402. The vibrational motion is coupled from the material 402 to the transducer 404, which generates electrical energy from the vibrational motion of the material 402. In this regard, the vibrational motion is coupled directly to the transducer 404, which directly generates electrical energy (e.g., electrical current) from the vibrational motion, without the need for an intermediate process, such as conversion of heat to electrical energy as would occur with use of a thermoelectric device, for example. The electrical energy (e.g., electrical current) output from the transducer 404 can be coupled to an electrical device e.g., electrical load 412, via the oscillator 406 and electrical leads 408.
The electrical load can be, for example, an output circuit (e.g., that converts high frequency AC current to a lower frequency current or DC current) in combination with an electrical device to be powered. As with other embodiments herein, it can be desirable to configure the system, e.g., the oscillator 406 and/or a suitable output circuit, to provide electrical power output at 50-60 Hz.
As with other embodiments disclosed herein, preferably, the material 402 contains a significant amount of D2 and/or HD (for example, 1-10 parts per thousand by number, or greater), and some smaller amount of 4He and/or 3He in equivalent sites (1-10 parts per million, or greater, for example). Exemplary frequencies for driving and operating the apparatus 400 (the overall system) are between about 1 Hz and about 1 GHz, with relatively lower frequency operation occurring between about 1 Hz and about 1 kHz and relatively higher frequency operation occurring between about 1 kHz and about 1 GHz. As will be understood by those of ordinary skill in the art, the frequency response of the transducer 404 and the frequency response of the oscillator 406 can be tailored to achieve an overall desired frequency response, e.g., so that operation on or near a resonance can be achieved, if desired, e.g., the response of the transducer 404/material 402 and the response of the oscillator can be substantially matched. In this way, a low order coupled transducer/material mode is driven on resonance. For example, a high-Q quartz crystal can be used as the transducer 404 and can be driven in the MHz range, with the quartz crystal being on the order of a millimeter thick, and with the sample being on the order of 100 microns thick. Lateral dimensions of the quartz crystal and sample can be on the same order, respectively. In the case of a liquid material 402 (e.g., liquid D2 or liquid mixture containing D2 suitably cooled in a suitable vessel), exemplary volumes can be on the order of about 1 cm3. Optimization so that operation can occur at about 50 Hz, 60 Hz or in the range of 50-60 Hz can be beneficial.
A highly-excited phonon mode in this case can be a hybrid electrical/phononic mode that is made up of the combination of a low-order phonon mode in the transducer 404 and material 402, and of the resonant electrical oscillator 406. Nuclear energy from the solid state reactions would go initially into this highly excited hybrid mode, which will sustain the mode if the overall Q is sufficiently high. Energy in this hybrid mode will thermalize through mechanical losses into heat in the sample, and through electrical losses into resistive losses in the electrical oscillator 406.
A low-resistance electrical load 412 can be coupled to the hybrid electrical-mechanical oscillator as shown in
Another example is illustrated in
In this example, the material 502 can be stimulated by any suitable excitation source such as previously disclosed herein or by an RF or microwave driver circuit (not shown) coupled to the cavity 506 by another waveguide (not shown). In either case, the material 502 is stimulated to promote nuclear reactions therein such as described earlier, and energy from the nuclear reactions is coupled into a variety of hybrid modes, wherein one component of the mode is mechanical such that it produces acceleration of the deuterium in the material 502. With such an hybrid mode, it is possible to utilize the transducer to couple mechanical and electromagnetic degrees of freedom.
In this example, the cavity 506 can be a high-Q RF or microwave cavity, which is coupled to a resonant high-Q combination of the transducer 504 and material 502. In this regard, the material 502 can be a high-Q solid material such as those mentioned above in connection with
Further Exemplary Embodiments with Modulated Stimulation
As discussed elsewhere herein, one type of coupling of interest in nuclear reactions in materials that comprise deuterium involves coupling the nuclear reaction to acoustic phonon modes of the material (phonon modes with frequencies from near zero to a few THz). To excite such acoustic modes with electromagnetic radiation from a source such as laser having output at visible, infrared (IR) or ultraviolet (UV) wavelengths, for example, the radiation can be modulated so that the modulation has a modulation frequency in the acoustic region. Numerous ways of modulating such light are known, including driving the laser with a driving circuit operating at a modulation frequency or using conventional shuttering devices including mechanical rotating shutters and electro-optical shutters, to name a few. In what follows, some exemplary embodiments using such modulated excitation sources to stimulate materials comprising deuterium to cause nuclear reactions therein are described. As will be appreciated, modulation of excitation sources to deliver modulated energy are not limited to electromagnetic sources, and the modulation frequencies are not limited to acoustic frequencies.
It will be appreciated that modulation as referred to herein includes both periodic and non-periodic dynamic changes in a property of the stimulation being applied, such as intensity, wavelength, heat flux, etc. Modulation is not limited to periodic modulations. Of course, periodic modulations such as regular sinusoidal, triangular or square wave variations, etc., in a property can be used. As noted above, it is believed that modulations of such stimulation can facilitate coupling to acoustic phonons in the materials containing deuterium, thereby facilitating generation of the nuclear reactions.
According to an exemplary embodiment, an apparatus can be configured such as illustrated in the block diagram of
With regard to the material 202, it is helpful to absorb the radiation in a way that is useful relative to the modulation frequency. For example, light absorbed in a metal sample penetrates less than 100 nm, which is suitable for coupling to a very wide range of acoustic mode frequencies. Also, it is known that the efficiency of acoustic wave generation in a material can be increased if a tamping layer (e.g., a coating such as a liquid) is present on the material.
The apparatus 200 also comprises a load 206 arranged to remove energy generated by the reactions from the material 202. The load 206 can be, for example, a heat exchanger, a thermoelectric device, a thermionic device, a thermal diode, a radiation absorber (e.g., a photovoltaic such as a photodiode) or an output transducer arranged to remove energy generated by the reactions from the material. In will be appreciated that the components illustrated in
In another example, the apparatus can be modified such that the excitation source 204 includes an input transducer, an electrical power source, or a particle-beam source, such as described elsewhere herein, instead of or in addition to using an electromagnetic radiation source. Other aspects of the apparatus 200 can be the same as already described.
In the context of a particle-beam source, a modulated KeV or MeV electron beam can be used wherein the modulation can be done at the electron source, with magnetic scanning, switching optics, or electrostatic optics, of types known to those of ordinary skill in the art. Alternatively, a modulated KeV or MeV ion beam could be use with a similar modulation scheme. Of course, ion beams are easily degraded, and a suitable environment such as a vacuum chamber, e.g., possibly with a small amount of deuterium gas therein gas, can be provided. Electron beams are considerably more penetrating, but such an embodiment would benefit from vacuum or low-pressure gas environments. It is possible to generate modulated high-power electron beams, ion beams, and laser beams very efficiently. Hence, it should be expected that modulated radiation drivers should be competitive.
In the context of stimulation with a transducer, it can be convenient to generate strong acoustic excitation for stimulation with piezoelectric transducers, in the regimes where they are applicable. Piezoelectric transducers for driving resonances in solids and liquids for excess heat applications can be useful over a wide range of frequencies, including but not limited to, the frequency range between about 1 kHz and about 1 GHz. At higher modulation frequencies, modulated laser sources can be relatively more beneficial compared to piezoelectric transducers considering the relative ease of developing good modulation at high frequency in laser sources and their ability to operate at elevated power and intensity levels. With regard to temperature, the performance of good piezoelectric materials may degrade at elevated temperatures. Thus, in some instances it can be more convenient to couple acoustic energy (both for stimulation and/or for output) above about 300 degrees C. using other approaches described herein other than with piezoelectric devices.
Hydraulically driven transducers can also be used for stimulation. For large systems, e.g., high-power generation systems, acoustic stimulation through hydraulic techniques can be advantageous to stimulate a large quantity of material 202 considering the existence of a mature pumping and plumbing technology.
In applications for heat generation, it can be advantageous to utilize a minimal system that is optimized for collecting and converting the reaction energy. In this case the stimulation required to initiate reactions can advantageously be provided by laser and other radiation sources.
It can also be convenient to generate large amounts of acoustical power mechanically with instabilities in forced fluid flow, e.g., in an instance where the material 202 is a deuterium containing liquid. Thus, for example, modulating the flow of such a liquid with an appropriate transducer such as a pump can be advantageous to generating reactions in the liquid.
As discussed above, an exemplary method for generating energy with a material 202 containing deuterium is provided, wherein the method comprises stimulating the material 202 to cause reactions in the material, wherein the material comprises at least one of molecular deuterium (D2) and molecular hydrogen-deuterium (HD), and removing energy generated by the reactions from the material. Exemplary approaches for stimulating and removing energy are described herein. In a further exemplary embodiment, the material 202 comprises D2 and comprises a species of atom capable of accepting excitation from the reactions, wherein a number of molecules of D2 is within 70% to 130% of a number of atoms of said species of atom. In a further exemplary embodiment, the material 202 comprises HD and comprises a species of atom capable of accepting excitation from the reactions, wherein a number of molecules of HD is within 70% to 130% of a number of atoms of said species of atom.
By substantially matching the number of molecules of D2 (or HD) to be within 70% to 130% of the number of atoms of the species of atom capable of accepting excitation from the reactions, an inversion as described herein can be readily achieved. An inversion can be achieved even more easily, efficiently and quickly if the number of molecules of D2 (or HID) is even more closely matched to the number of atoms of the species of atom capable of accepting excitation from the reactions, e.g., such that the number of molecules of D2 (or HD) is within 80-120%, 90-110%, 95-105%, 98-102% or 100% of the number of atoms of the species of atom capable of accepting excitation from the reactions.
In connection with these examples, without being bound by particular theoretical considerations, phonon-exchange models are discussed below. The question of the deuteron-deuteron separation is addressed, and what materials maximize overlap and concentration. A new figure of merit is proposed that depends on the D2 concentration to the 3/2 power and the square root of the fusion rate. A simplified picture of the dynamics is discussed in which the problems of excitation transfer and energy coupling between nuclear and low energy degrees of freedom are separated. The dynamics of the excitation transfer in a simple unbalanced model is discussed. A new classical picture for coupling with phonons is discussed. An excess heat example with the unbalanced excitation transfer model is also discussed.
In recent years the focus of our theoretical effort on anomalies in metal deuterides has focused on coupled nuclear and phonon models. [P. L. Hagelstein, “A Unified Model for Anomalies in Metal Deuterides,” Proceedings of the 8th International Conference on Cold Fusion, Lerici (La Spezia), Italy, May 2000; p. 363; P. L. Hagelstein, “A Unified Model for Anomalies in Metal Deuterides,” Proceedings of the 9th International Conference on Cold Fusion, Beijing, China, May 2002; p. 121.] In connection our theoretical work, by considering condensed matter effects at the outset of a nuclear calculation, then the new effects responsible for the anomalies are included in a natural way. Among the significant new effects are new site-other-site interactions, in which nuclei at one site are coupled to nuclei at other sites through phonon exchange with a common highly-excited phonon mode.
In a lengthy write-up in the ICCF10 proceedings, we described the model (and the associated ideas), and discussed what we viewed as connections with a wide variety of experimental observations. [P. L. Hagelstein, “Unified phonon-coupled SU(N) models for anomalies in metal deuterides,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003 (in press).] Theoretical issues that have been considered so far include:
The model appears to be relevant to a wide variety of experimental observations in the cold fusion field, as we have discussed previously. [P. L. Hagelstein, “Unified phonon-coupled SU(N) models for anomalies in metal deuterides,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press).] Some of the specific connections with experiment that we have discussed include:
We have discussed previously the presence of deuterium in what amounts to a molecular state within the condensed matter environment, as the tunneling matrix element is reduced by many orders of magnitude if this condition is not satisfied. We are interested here in some of the consequences that result.
The thermodynamics of hydrogen atoms in metals has a long history, with a primary focus on the solubility of hydrogen in metals in equilibrium with molecular hydrogen gas. Hydrogen solubility in the case of palladium was understood at a basic level many years ago by Lacher. [J. R. Lacher, “A theoretical formula for the solubility of hydrogen in palladium,” Proc. Roy. Soc. (London) A161, 525 (1937).] In this model, the dependence of the hydrogen binding energy in the metal on hydrogen loading was taken into account, generalizing previous results, and resulting in reasonably good agreement with experiment. We are interested here in the question of double occupancy for palladium deuteride, for example, since we presume that to within an excellent approximation deuterons not in close proximity do not participate in the new processes that we are interested in.
For this calculation, we can determine the occupation probability (of a single site) from
where gj is the statistical weight of state j; where Ej is the state energy; where Nj is the number of deuterons in the state, and where μ is the chemical potential of the deuteron. To proceed, we need simply to enumerate the states and their associated weights and energies. However, there is very little relevant data available for the states, and almost no relevant models for the energy levels in the case of double occupancy. Hence, an alternative approach can be useful.
We therefore turn our attention to the loading as a function of the chemical potential. If we assume that the fraction of deuterons in states with double occupancy is small, and also that tetrahedral site occupation can be neglected, then the probability that a site is occupied is
If we identify x with the single-site occupation probability p[D], then we may express the term containing the chemical potential in terms of the loading
Using a similar approximation, we can estimate the probability of double occupancy to be
We eliminate the chemical potential to give
At this point, results from much more sophisticated models or from experiment are useful. We expect that double occupancy in bulk Pd is not favorable, as the energy difference Ej−2ED (which is essentially a D2 binding energy within the metal deuteride) is probably positive and large. Such a conclusion was reached in the density functional calculations of Sun and Tomanek [Z. Sun and D. Tomanek, “Cold fusion: How close can deuterium atoms come inside palladium,” Phys. Rev. Lett. 63, 59 (1989)], and also in other calculations as well. (See F. Liu, B. K. Rao, S. N. Khanna, and P. Jena, “Nature of short range interactions between deuterium atoms in Pd,” Solid State Communications 72, 891 (1989); P. K. Lam and R. Yu, Phys. Rev. Lett. 63, 1895 (1989); O. B. Christensen, P. D. Ditlevsen, K. W. Jacobsen, P. Stolze, O. H. Nielsen, and J. K. Norskov, “H-H interactions in Pd,” Phys. Rev. B 40, 1933 (1989); X. W. Wang, S. G. Louie, and M. L. Cohen, “Hydrogen interactions in PdHn (1≦n≦4),” Phys. Rev. B 40, 5823 (1989); S.-H. Wei and A. Zunger, “Stability of atomic and diatomic hydrogen in fcc palladium,” Solid State Communications 73, 327 (1990); A. C. Switendeck, “Electronic structure and stability of palladium hydrogen (deuterium) systems, PdH(D)n, 1≦n≦3,” J. Less Common Metals 172-174, 1363 (1991)). We note that the D2 molecular state in bulk Pd in these calculations is also unstable, thus prompting further consideration on where molecular D2 states are found. Some have questioned the position that the anomalies are associated with bulk Pd. See E. Storms, “What conditions are required to initiate the LENR effect?” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press).
To proceed, we first note that the summation can be divided into ortho- and para-deuterium contributions
This corresponds to the fact that even angular momentum states occur only for total nuclear spin S=0, 2, and that odd angular momentum states occur only for total nuclear spin S=1 (see H. L. Johnston and E. A. Long, J. Chem. Phys. 2, 389 (1934)). The molecular ground state (l=0) has a larger tunneling matrix element than that associated with higher rotational angular momentum states. Consequently, it makes sense to focus on the l=0 molecular ground state, in which case we may write
From the local density approximation results, the energy difference E0−2ED is on the order of 1 eV or greater, which precludes any significant fractional occupation in bulk Pd. In a simplified model for confined molecular deuterium (D2), one can conclude that the electronic contribution is dominant in the determination of E0−2ED in the local density approximation calculations. Note that H2 in solids and liquids has been of interest in the literature. For example, Henis and coworkers discuss the impact of confinement on the cold fusion rate. [Z. Henis, S. Eliezer, and A. Zigler, J. Phys. G: Nucl. Part. Phys. 15, L219 (1989).] Darby et al. discuss a crystal field theory for H2 in relation to the problem of solid hydrogen. [M. I. Darby, S. Papaconstantinopoulou, and K. N. R. Taylor, “A crystal field theory for molecular hydrogen,” J. Phys. C: Solid State Physics 13, 2881 (1980).] Hunter et al. have focused on transitions between rotational states to account for the lineshape observed in water. [J. E. Hunter, D. G. Taylor III, and H. L. Strauss, “Calculation of the rotational Raman spectrum of H2 dissolved in water,” J. Chem. Phys. 97, 50 (1992). This will presumably be different depending on the local chemical environment. Our expectation is that the D2 state is less exothermic in the vicinity of a host lattice atom vacancy. There exist calculations specific to hydrogen and deuterium near such a defect (see P. Nordlander, J. K. Norskov, F. Bessenbacher, and S. M. Myers, “Multiple deuterium occupancy of vacancies in Pd and related metals,” Phys. Rev. B 40, 1990 (1989); F. Bessenbacher, B. Beck Nielsen, J. K. Norskov, S. M. Myers, and P. Nordlander, “Interaction of hydrogen isotopes with metals: Deuterium trapped at lattice defects in palladium,” J. Fusion Energy 9, 257 (1990); K. Tsuchiya, Y. H. Ohashi, K. Ohashi, M. Fukuchi, “Interaction between two neighboring deuterium atoms in palladium,” J. Less Common Metals 172-174, 1371 (1991)), but useful estimates of E0−2ED are not presently available.
In the absence of relevant excitation energy estimates from the literature, we are inclined to turn to experimental results in excess heat experiments, where activation energies have been measured. The excess heat is observed to have a local dependence on temperature of the form
Pxs˜exp(−ΔE/kBT)
where ΔE is 670 meV as reported by Storms (E. Storms, “Some characteristics of heat production using the ‘cold fusion’ effect,” Proceedings of the Fourth International Conference on Cold Fusion, December 1993 Maui, Hi., edited by T. O. Passell and M. C. H. McKubre, Vol. 2, p. 4-1) in an electrochemical experiment, 630 meV by Swartz (M. R. Swartz, “Photo-induced Excess Heat from Laser-Irradiated Electrically Polarized Palladium Cathodes in D2O,” Proc. ICCF10, Cambridge, Mass., 2003) in an electrochemical experiment, and 560 meV as reported by Case (L. Case, in his oral presentation at ICCF10 (2003)) in a gas loading experiment. If one asserts that the excess power is linear in the D2 concentration, then these activation energies should be interpreted directly in terms of a promotion energy. Later herein, the unbalanced excitation transfer between D2 and many host nuclei, in which the maximum associated rate is proportional to the 3/2 power [so that Pxs˜exp{−( 3/2)(E0−2ED)/kBT}] will be discussed. In this case we would take
E
0−2ED=370−450 meV
The relative difficulty of achieving a high D2 occupation in metal deuterides suggests alternate routes to develop useful samples for cold fusion experiments and applications. The simplest solution to the problem should be in the use of solids which contain molecular D2 (or HED in the case of the proton-deuteron pathway) as a primary constituent. In one example, we consider that the material 202 which comprises at least one of D2 and HD also comprises an isotopic variant of a dihydrogen transition metal complex with a substitution by at least one of D2 and HD, in which case the species of atom capable of accepting excitation from reactions can be a transition metal constituent of said material 202, e.g., selected from molybdenum, chromium, tungsten, ruthenium and iron. Hydrogen bonding in molecules and solids has a very long history, and over many decades there was no indication that two hydrogen atoms could develop sigma bonding in a molecule or complex. However, such in 1983 it was shown that intact molecular H2 could bond more or less as a molecule to a transition metal complex. [G. Kubas, Metal dihydrogen and σ-bond complexes, Kluwer Academic/Plenum Publishers, New York, (2001).] In recent years, research on dihydrogen molecular complexes has been an important area of inorganic chemistry, with a large number of examples, and also with corresponding IR and NMR studies that help clarify the local interaction between the protons.
Dihydrogen molecule complexes span a continuous range of behavior from near molecular behavior to near dihydride behavior. The separation between protons in H2 is 0.74 Å. The separation between protons in the complex Cr(CO)3(P/Pr3)2(H2) is measured by solid state NMR to be 0.85 Å. Separation distances in more classical transition metal dihydrides are on the order of 1.6 Å. Examples of some dihydrogen complexes are given in Table 2. There are issues associated with the x-ray and neutron measurements that have to do with libration correction, which can lead to an underestimate of the proton-proton distance. This is one factor in the appearance of smaller numbers associated with the x-ray and neutron diffraction results.
Thus, it is believed that the use of isotopic metal dihydrogen complexes in cold fusion experiments can be beneficial (the material which comprises at least one of D2 and HD also comprises an isotopic variant of a dihydrogen transition metal complex with a substitution by at least one of D2 and HD). The fractional occupation of D2 in these materials will be much greater than in metal deuterides, and there are advantages in working with a well-studied material in which the separation distance is known. One question of interest in such a venture is how much is the tunneling matrix element reduced in these systems? To estimate this, we can take advantage of the interpolation formula of Bracci and coworkers [L. Bracci, G. Fioentini, and G. Mezzorani, “nuclear fusion in molecular systems,” J. Phys. G: Nuclear Physics 16, 83 (1990)] which in the case of the dd-reaction can be written in the form
where k1=3×1024 cm−3, C is the reaction constant 1.5×10−16, k2 is a fitting constant (which is 3.51 for D2 and 3.41 for D2+), μ is the reduced mass of the nuclei, me is the electron mass, and a0 is the Bohr radius. We have modified this formula by making k2 an explicit function of d.
In addition, we have added 0.40 to the Log10 of the rate in sec−1 to obtain slightly better agreement with accurate calculations.
Another way to arrange for molecular D2 to be present in a condensed matter environment is to take advantage of the finite solubility that is naturally available. For example, H2 is soluble in heavy ice (as cited in Z. Chen, H. L. Strauss, and C.-K. Loong, J. Chem. Phys. 110, 7354 (1999)) at a level of 9.4×10−4 M/atom at 0° C. The rotational energy of H2 as measured by neutron scattering is less than that for free H2, which can be interpreted in terms of an increase in the proton-proton separation. According to Z. Chen, H. L. Strauss, and C.-K. Loong, J. Chem. Phys. 110, 7354 (1999), the reduction is about 3%, which is consistent with an increase of the proton-proton separation by 1.3 Å. This is interesting, because it is much closer to the pure molecular H2 separation than we have seen in earlier examples, and leads to a coupling matrix element 2-3 orders of magnitude larger than in the case of isotopic dihydrogen compounds. In the case of H2 in solid argon, spectroscopic observations are consistent with an increase in the equilibrium separation from free H2 by 0.0028 Å [R. J. Kriegler and H. L. Welsh, “The induced infrared fundamental band of hydrogen dissolved in solid argon,” Can. J. Phys. 46, 1181 (1968)], which is indicative of an even weaker interaction as expected.
As remarked above, the formation of sites with double hydrogen occupancy in palladium hydride is enhanced in the presence of defects. (specifically, single atom host lattice vacancies). According to Pavesi and Gianozzi, hydrogen in GaAs forms molecular H2 in tetrahedral sites, which are deep wells for the molecular state. [L. Pavesi and P. Giannozzi, “Atomic and molecular hydrogen in gallium arsenide: A theoretical study,” Phys, Rev, B 46, 4621 (1992).] Linn Hobbs has suggested that molecular hydrogen goes into vacancies in NaCl. [private communication] Theoretical studies for hydrogen in silicon indicate that molecular H2 should form in Si. [P. Deak, L. C. Snyder, and J. W. Corbett, “State and motion of hydrogen in crystalline silicon,” Phys. Rev. B 37, 6887 (1988); C. G. Van de Walle, P. J. H. Denteneer, Y. Bar-Yam, and S. T. Pantelides, “Theory of hydrogen diffusion and reactions in crystalline silicon,” Phys. Rev. B 39, 10791 (1989).] The implication is that if these materials are loaded with deuterium, presumably at high deuterium pressure and temperature that molecular states will form in the bulk. The kinetics of this process according to these results is much favored energetically over the case of PdD once the deuterium is in the lattice. However, it is expected that the solubility of hydrogen in the semiconductors will be much less.
In another example, the material 202 can comprise a fullerene-based material, wherein said species of atom is selected from the group consisting of lead, tin, germanium and silicon. As a further example, the material can comprise a fullerene-based material, wherein said species of atom is selected from the group consisting of rubidium, potassium, sodium, cesium and barium.
Since it was announced that C60 occurs as a fullerene, chemists have sought to develop materials in which various atoms or molecules are isolated within the interior of the cage of the fullerene. Over the years, research efforts have focused on the possibility of including molecular H2 in the interior of a fullerene, with mostly limited success until recently. Previous work on inert gas encapsulation involved heating the fullerenes in a rare gas atmosphere [R. J. Cross and M. Sanders, Fullerenes—Fullerenes for the New Millennium, Electrochemical Society Proceedings, Volume 2001-11, 298 (2001)] (which produced a very low yield) and acceleration of rare gas atoms into stationary fullerenes. In the latter case, the atom could slip through the cage with sufficient noble gas atom velocity, and be encapsulated with significantly higher yield. The encapsulation of 3He and 4He has been reported through this method. Methods to purify fullerenes with encapsulated atoms are discussed in Y. Kubozono, “Encapsulation of an atom into C60 cage,” in Endofullerenes, A New Family of Carbon Clusters, edited by T. Akasaka and S. Nagase, Kluwer Academic Publishers, Dordrecht (2002).
In 2003, Murata and colleagues published a paper claiming a method that allowed for 100% yield of molecular hydrogen into an open-cage fullerene derivative [Y. Murata, M. Murata, and K. Komatsu, J. Am. Chem. Soc. 125, 7152 (2003)], and gas phase generation of H2 in C60. A discussion of the issues associated with such an open-cage structure, and the synthesis of this structure, is discussed in G. Schick T. Jarrosson, and Y. Rubin, Angew. Chem. Int. Ed., 38, 2360 (1999). The encapsulation of H2 in the open-cage structure was achieved by exposing a powder made of the open-cage fullerene to 800 atmospheres of H2 at 200 C for 8 hours. No loss of H2 from the open-cage structure in a solution was observed at room temperature over 3 months, and H2 release was observed at 160° C. and above. These results imply the possibility of working with D2 or HD encapsulated open-cage fullerene structures in solution (see the next section on the use of liquids), as reported in Murata et al., or with D2 or HD in closed cage structures in solution or as solid structures.
Molecular H2, HD and D2 encapsulated in C60 was studied using NMR by Tomaselli and Meier. [M. Tomaselli and B. H. Meier, “Rotational-state selective nuclear magnetic resonance spectra of hydrogen in a molecular trap,” J. Chem. Phys. 115, 11017 (2001).] From the results of this study, one concludes that the molecular ground state within the cage is very nearly the same as in the free case. A relatively small crystal field splitting is observed for the first rotational states, where the first rotational state energy for HD is split to roughly 92 and 99 cm−1 as compared to the free space value of 89.4 cm−1. Rubin and coworkers also studied encapsulated molecular hydrogen in an open cage fullerene by NMR. [Y. Rubin, T. Jarrosson, G.-W. Wang, M. D. Bartberger, K. N. Houk, G. Schick, M. Saunders, R. J. Cross, “Insertion of helium and molecular hydrogen through the orifice of an open fullerene,” Angew. Chem. Int. Ed. 40, 1543 (2001).] In this work, the NMR signal for ground state HD inside the cage was split into a triplet with an associated coupling constant of 41.8 Hz, which is somewhat less than the free HD value of 43.2 Hz (which indicates that the proton-deuteron separation is close between the two cases). This can be compared with a similar splitting in the case of a deuterated dihydrogen complex W(CO)3(P/Pr3)2 (HD), where the coupling constant is 33.5 Hz, and the proton-proton separation is reported to be 0.89 Å.
Fullerenes have been made into solid structures through a variety of methods (as described in K. Prassides and S. Margadonna, “Structures of Fullerene-Based Solids,” in Fullerenes: Chemistry, Physics, and Technology, edited by K. M. Kadish and R. S. Ruoff, Wiley-Interscience, NY (2000)). Crystalline powders of C60 were found by x-ray diffraction to form random collections of hcp and fcc lattice structures formed of nearly spherical fullerenes with interstitial spaces (that can be filled). The formation of similar solids is expected in the case of D2 and HD encapsulation. Also, as discussed previously herein, intercalated fullerides are known, in which various atoms are placed into the interstices, which can lead to interesting physical effects such as superconductivity, as has been observed in alkali fullerides, wherein the alkali atom (which is intended to refer to alkali and alkaline-earth metals) can be, for example, Rb, K, Na, Cs or Ba. It is believed that such materials can be produced with D2 and/or HD inserted therein by heating such material in the presence of D2 and HD gas at elevated temperature and pressure for use as the material 202 in
There appears to be nothing within the models that we have studied that would prevent reactions taking place in a liquid, as long as the phonon excitation involves a relatively long wavelength such that nuclei do not move away from an amplitude maximum quickly. Metal dihydrogen complexes can occur in solution as one approach. Additionally, D2 is known to go into liquid solution with significant solubility under a pressurized deuterium gas atmosphere.
It might reasonably be asked whether D2 in a liquid is similar to free D2. The rotational Raman spectrum of H2 in water was presented in D. G. Taylor III and H. L. Strauss, “The rotational spectrum of H2 in water,” J. Chem. Phys. 90, 768 (1989). The focus in this work was on the question of the Raman line shape, which is broadened in the liquid environment. A comparison of the spectrum in water as compared with gas presented in this work shows a shift of about 5%, which is consistent with a change in the separation by about 0.019 Å, indicative that the low-lying states in liquid are not very different from those in free space, which is desirable.
As a step toward evaluating candidate materials for cold fusion research, it is of interest to develop a measure of how good one material is relative to another material. If we focus only on the issues of how much molecular deuterium there is, and on how large the tunneling matrix element is, then we can develop a figure of merit that can be used to characterize a material with respect to these issues. There are other issues as well, which may be pertinent in developing a more universal figure of merit. According to our modeling, excess power should go as the three-half power of the number of D2 molecules embedded in condensed matter, and linear in the tunneling matrix element. Consequently, it seems reasonable to adopt a figure of merit that is proportional to (concentration)3/2, and also proportional to the square root of the conventional fusion rate. We define a figure of merit for the DD→4He path defined according to
We normalize the fusion rate γDD in this case to that of molecular D2 (γDD0), for which accurate theoretical estimates exist. We normalize the concentration nDD to that of solid molecular deuterium (nDD0), which has a known and large concentration.
A short table of selected candidates has been developed in Table 3. One sees that the figure of merit for liquid deuterium is close to that of solid deuterium, but is reduced because of the density. D2 in cyclohexane looks extremely interesting under the assumption that the deuteron-deuteron separation is close to that of D2 in water. D2 encapsulated in C60 is also very interesting. In these cases, it is primarily the concentration effect that brings down the figure of merit. The isotopic transition metal deuterides are hindered because of the larger deuteron-deuteron spacing. It would be reasonable to ask what the associated figure of merit is for the Fleischmann-Pons experiment, or the Szpak experiment. If the observed dependence of the heat effect is in fact due to a requirement for excitation to D2 states as we have conjectured, then the D2 concentration may be as large as a few times 1019 cm−3. The deuteron-deuteron separation is unknown at present. If we assume an optimistic separation of 0.85 Å, then the resulting figure of merit will be on the general order of 10−8.
The problem of reaction dynamics is in general complicated but quite interesting. Our purpose in this section is to discuss a simple way of looking at the problem which may allow us to enhance our understanding. We begin by looking at the different functions which are required. In the most basic view, there are three issues at hand:
In what follows, we will separate the population dynamics from the coupling of the energy to the condensed matter. This will be a tremendously helpful separation conceptually.
To obtain an accelerated tunneling rate, we want a coherent enhancement as was discussed in papers presented at ICCF10 (P. L. Hagelstein, “Unified phonon-coupled SU(N) models for anomalies in metal deuterides,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press) and P. L. Hagelstein, “Resonant tunneling and resonant excitation transfer,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press)). Such an enhancement, can be achieved using a collection of two-level systems that make a downward transition, with equal coupling to a common oscillator (or other extended quantum system), and a second collection of two-level systems that make an upward transition through coupling to the same common oscillator.
Given this approach, the question arises as to what equivalent two-level systems we should consider. For the initial set, we take the molecular D2 states embedded in condensed matter as the upper state, and 4He as the ground state. For the second set, other systems can be considered. We have considered two general kinds of states for the second set. In one case, excitation from 4He to n+3He compact states is a reasonably natural choice, as it is possible to have angular-momentum stabilized compact states in the general vicinity of the D2 energy.
The second kind of states which may accept the excitation are similar states in other nuclei within the condensed matter. For example, in the case of PdD experiments, there are analogous transitions in Pd which are expected to show a similar behavior. In this case, one or more neutrons are removed from a Pd nucleus to form a high angular momentum compact state, with a similar mechanism used to transfer angular momentum from the compact state.
The many-site problem that comes out of the lattice resonating group method is very complicated, and we have sought to simplify the picture. In this paper, we propose a quite drastic simplification which may be useful. On the one hand, there is excitation transfer from the D2 molecular state to excited states of other nuclei. On the other hand, there is coupling to a highly excited low energy mode, which exchanges nuclear energy for phononic energy, or energy in other modes. Both occur at the same time, which makes the problem quite complicated. As discussed here we simply separate the two functions, and look at each individually.
We consider here the transfer of excitation from the D2 states to resonant compact states composed of a daughter nucleus with a neutral partner with high angular momentum. We do not expect a precise resonance to occur, so we imagine that either through some phonon exchange or other routes that a suitable response of the lattice and nuclear system occurs at a matched frequency, that we can think about in terms of an equivalent matched two-level Dicke system. We analyzed the dynamics of this kind of system previously in the case of matched populations. [P. L. Hagelstein, “Unified phonon-coupled SU(N) models for anomalies in metal deuterides,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press); P. L. Hagelstein, “Resonant tunneling and resonant excitation transfer,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press).] Here, we are interested in what happens when the populations are not matched. In this case, we assume that there occur appropriate resonant states in the host lattice, and that there are many more nuclei of whichever isotope has the best match than there are D2 molecules. In this case, we have an unbalanced coherent Dicke transfer. Resonant excitation transfer occurs in this system much the same as in the case of the matched case we reported on earlier. Results for a representative calculation are shown in
One sees in this calculation that the population stays localized in the initial state for some time, and then a rapid transition of the excitation from one two-level system to the other occurs. In the matched system, the excitation stayed for a significant time in the other two-level. In the unmatched system, the population returns rather quickly back to the initial state. This is quite interesting. From the results of many calculations, this behavior is repeated with essentially only a change in scale factor. We find that
The associated transition rate as a function of time is illustrated in
The second part of the simplification discussed in the previous section involved the coupling of energy between the nuclear system and other lower-energy degrees of freedom. Here we will focus on coupling to a highly excited phonon mode. Qualities of the highly excited phonon mode appear to be different for the initial excitation transfer as discussed above (where a single mode interacting with all nuclei is best) and for energy transfer (where more localized modes may be useful since the coupling is much stronger). The lattice generalization of the resonating group method leads to a picture in which excitation is transferred rapidly from on site to another, with a small amount of phonon exchange occurring with every site change. We examined a model for the associated energy exchange previously using a quantum flow calculation, which suggested that this mechanism for energy exchange between the two quantum systems is very efficient. Here, we are interested in another model for energy exchange.
Suppose that the phonon mode in question has regions where the vibrational motion is locally large, and other regions in which the vibrational motion is much less. Suppose also that the hopping of excitation from site to site is effective, so that the excitation is able to move between the two regions over an oscillation cycle. In this case, we have the possibility of using classical estimates to determine the maximum rate at which net energy exchange occurs. The natural associated classical picture that is suggested is that where excitation is present, the excited nuclei look lighter to the condensed matter (since neutral particles are effectively decoupled). If the excitation oscillates between regions of high vibrational amplitude and low vibrational amplitude, then this can produce net energy gain in the condensed matter. We can estimate how much in the case of lattice vibrations through the following calculation
The maximum power increase is obtained with when the mass decreases during maximum kinetic energy, which can occur with mass modulation at twice the mode frequency. In this case, an estimate for the maximum power is
where ƒ* is the fraction of nuclei that are excited,
is the fractional mass difference due to the presence of excitation, ω0 is the oscillation frequency, and where E0 is the mode energy.
This result motivates us to think further about the associated dynamics. If we were to match the number of D2 molecules involved substantially to the number of nuclei that can accept the excitation, then we would end up with an inverted two-level system which we now imagine is to dump its excitation to the phonon mode. In this case, we would expect the associated dynamics to resemble that of laser dynamics, in that net gain should be present for all highly excited modes such that ƒ*Δm/4M is greater than the Q of the mode. Net gain should be present transiently also if the number of accepting nuclei is less than the number of D2 molecules, or greater by less than 2. In either case, one would expect that the nuclei would make use of the above mechanism to dump energy, and that phonon amplification should occur. If the initial and final sets are not well matched such that there are more nuclei accepting excitation, then the dynamics presented above indicates that a significant compact state excitation will be present, but no inversion and no gain. Under these conditions, the excited nuclei would couple incoherently as a very hot source, with an associated power transfer rate that would depend on the strength of excitation of the modes.
Thus, it can be desirable to substantially match the number of D2 molecules in condensed matter to the number of nuclei that can accept the excitation. If we assume that carbon and other low mass nuclei are not well-matched at 24 MeV, then it may become possible to take advantage of isotopic dihydrogen compounds for this purpose. An isotopic transition metal dihydrogen compound can have one metal atom per D2 molecule, which leads to matched populations. In the case of fullerene-based systems, it would be possible to match the concentration of encapsulated D2 with the concentration of encapsulated heavy atoms that can accept the excitation (for example, Kr or Xe in the case of noble gases). Alternatively, in fullerene polymers, it is possible to include heavier atoms interstitially so that the number of such atoms is matched to the number of buckyballs, which satisfies the gain condition if D2 is encapsulated in some fraction of the buckyballs. Of course, it is not necessary to exactly match the number of D2 molecules in condensed matter to the number of nuclei that can accept the excitation. But an inversion can be achieved more easily, efficiently and quickly if the number of molecules of D2 (or HD) with the closer the match to the number of atoms of the species of atom capable of accepting excitation from the reactions, e.g., such that the number of molecules of D2 (or HD) is within 70-130%, 80-120%, 90-110%, 95-105%, 98-102% or 100% of the number of atoms of the species of atom capable of accepting excitation from the reactions.
Armed with the results in the previous sections, it seem reasonable to revisit the heat pulse calculation that we presented in P. L. Hagelstein, “Unified phonon-coupled SU(N) models for anomalies in metal deuterides,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press). To proceed, we require an estimate for the tunneling factor e−G. It is possible to make use published results for the molecular D2 problem. We may write
where vmol is the volume associated with the molecule. It is possible to develop an estimate for |ψ(0)|2 from calculations of γDD, combined with the reaction constant
γDD=A|ψ(0)|2 (15)
where A is 1.5×10−16 cm3/sec. This gives |ψ(0)|2 to be 2.0×10−48 cm3. If we take vmol to be 1.4×10−24 cm3, we conclude that
e
−G=1.7×10−36
for free molecular D2. To be consistent with this way of looking at things, we revise our rate formula to read
where U is the effective interaction strength for the coupled reactions measured on a nuclear volume vnuc.
For a heat pulse that lasting 5 hours, the maximum reaction rate of 1012 sec−1 produced 5.65×1016 final state 4He nuclei. We can analyze the reaction rate formula for self-consistency as follows. The deuteron-deuteron separation distance d is not well known in the experiment, so we will adopt it as a parameter. We also do not know whether all of the host nuclei participate, or whether only a few matched isotopes participate. Hence we determine the number needed as a function of the separation distance, matching the peak reaction rate
The result of such a computation is illustrated in
Other systems of interest include the Kasagi 3-body accelerator experiment [J. Kasagi, T. Ohtsuki, K. Ishu and M. Hiraga, Phys. Soc. Japan 64, 777 (1995)], the fast alpha emission experiments [A. G. Lipson, G. H. Miley, A. S. Roussetski, and E. I. Saunin, “Phenomenon of energetic charged particle emission from hydrogen/deuterium loaded metals,” Proceedings of the 10th International Conference on Cold Fusion, Cambridge, Mass., August 2003; (in press)], the search for 3He, and in experiments that involve lattice excitation mechanisms.
It should be emphasized that although illustrative embodiments have been described herein in detail, that the description and drawings have been provided for purposes of illustration only and other variations both in form and detail can be added thereupon with departing from the spirit and scope of the invention. The terms and expressions herein have been used as terms of description and not terms of limitation. There is no limitation to use the terms or expressions to exclude any equivalents of features shown and described or portions thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11/137659 | May 2005 | US | national |
The present application claims the benefit of U.S. patent application Ser. No. 11/137,659 filed May 26, 2005, U.S. Provisional Patent Application No. 60/623,772 filed Nov. 1, 2004, and U.S. Provisional Patent Application No. 60/714,263 filed Sep. 7, 2005, the entire contents of each of which are incorporated herein by reference. U.S. patent application Ser. No. 11/137,659 is a continuation-in-part of U.S. patent application Ser. No. 10/440,426 filed May 19, 2003, which is a continuation of U.S. patent application Ser. No. 10/441,891 filed May 17, 2003, which claims priority to U.S. Provisional Application No. 60/449,247 filed on Feb. 14, 2003 and U.S. Provisional Application No. 60/381,863 filed on May 18, 2002.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/40134 | 11/1/2005 | WO | 00 | 12/10/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60623772 | Nov 2004 | US | |
| 60714263 | Sep 2005 | US |
