Patent Application
20070114380
A. Field of the Invention
Embodiments herein relate to the field of charged particle storage and transportation. More particularly, embodiments relate to apparatus and method of storing and transporting charged particles, as well as preparing, filling, and transporting a bottle capable of storing and transporting charged particles utilizing electrostatic containment. More specifically, the present invention addresses the collection and storage of antiprotons; and the transport of antiprotons.
B. Background of the Invention
Antiprotons are annihilated upon contacting matter, and containers (e.g., Penning traps) include: “Container for Transporting Antiprotons,” U.S. Pat. No. 5,977,554 issued to Gerald A. Smith, et al. on Nov. 2, 1999; “Container for Transporting Antiprotons,” U.S. Pat. No. 6,160,263 issued to Gerald A. Smith, et al. on Dec. 12, 2000. See also Smith et al's. related U.S. Pat. Nos. 6,414,331 and 6,576,916, all of which are incorporated by reference. U.S. Pat. No. 5,977,554, for example, teaches containing with “means for providing the necessary magnetic fields”; “cryogen or cold wall”; and antiprotons are trapped in a potential well formed between the first and second electric fields (italics added herein.)
While embodiments herein stand on their own, some embodiments reflect removal of that which has previously been considered necessary or otherwise contradict prior teachings.
Antiprotons can be generated and used in experimental studies typically performed by using large particle accelerators, such as the Tevatron at the Fermi National Accelerator Laboratory (Fermilab). The Fermilab accelerator complex includes various linear accelerators and synchrotrons to generate antiprotons, to accelerate these antiprotons to very high energies and momenta (typically to 1 TeV), and to collide these antiprotons together with protons. The results of the collisions can be analyzed to provide information regarding the structure and physical laws of the universe.
While these experimental studies of particle physics use antiprotons with very high energies and momenta, other uses of antiprotons, such as the medical use, have relatively small energies and momenta. If the existing sources of antiprotons at such accelerators are to be used as sources of antiprotons for these other fields, the antiprotons have to be decelerated (i.e., energy and momentum of the antiprotons will have to be reduced). Consider the use of the Main Injector at the Fermi National Accelerator Laboratory (FNAL) in Batavia, IL as a particle decelerator (instead of its nominal role as an accelerator), and incorporated by reference are U.S. Pat. Nos. 6,838,676 and 6,822,045. In addition, to provide antiprotons to locations that are off-site from the particle accelerators, the antiprotons have to be decelerated sufficiently to enable them to be stored in a portable synchrotron or cyclotron, or trapped in a bottle and transported to other locations.
One embodiment provides means for storing charged particles, such as antiprotons. The means for storing can include an electrostatic means, such as a bottle, and preferably the means for storing can be utilized as a means for transporting. The means for storing can facilitate applications: For example, the treatment of cancerous tissue, the generation of radioisotopes within the body (useful for imaging techniques and therapeutic treatment).
An electrostatic bottle can be comprised of one or more electrodes through which charged particles flow. Each electrode has applied to it a specific voltage. The combination of electrode spacing, voltage, and aperture diameter, coupled with the motion of the charged particles within the bottle, creates a focusing force which constrains the particles from striking any surfaces within the bottle.
As to the particle motion dynamics of the stored antiprotons, the design of charged particle storage rings can rely on the employment of piecewise uniform (and hence integrable) optical elements such as dipole and quadrupole magnets. By using such linear optical elements which have analytic solutions for particle trajectories and amplitude independent stability parameters, particle loss effects such as resonant extraction and dynamic aperture can be controlled or avoided at the design stage of the optical system. In some embodiments, it can be preferable to sharpen the edges of the discrete focusing and defocusing lenses, depending on the preferred integrable solution desired for predicting long-term storage.
By way of a prophetic teaching, a design can employ an optical system composed of tens or hundreds of electrodes. A representative design can be simulated to illustrate synthesis of piecewise integrable electrostatic optical systems. The choice of electrode voltages utilize an accelerator physics approach to storage ring design in which a piecewise integrable optical system can be used to minimize dynamical sources of particle loss.
By way of another prophetic teaching, the optical system can be comprised of axisymmetric electrodes. Alternatively, the optical system can be comprised of electrostatic quadrupoles, employing strong-focusing to generate a net focusing force on charged particles that are moving within the bottle. Also, the optical system can be comprised of both axisymmetric electrodes and electrostatic quadrupoles.
By way of another prophetic teaching, the geometry of the bottle can incorporate a linear array of electrodes, in which the charged particles oscillate across the bottle along the axis of the electrodes. Alternatively, the bottle can contain a ring of electrodes, in which the charged particles continuously circulated round the ring in toroidal geometry.
In order to maximize the storage life of the charged particles within the bottle, the voltage on the electrodes can be slowly modified. This modification can be based on measured properties of the stored charged particles, such as their oscillation frequencies within the focusing electric field.
A vacuum can be used to prevent the stored particles from being lost through chemical reactions, nuclear reactions, or particle-antiparticle annihilation. In order to keep the weight of the bottle low, the skin of the primary vacuum system can be quite thin. If exposed to air, which contains a hydrogen partial pressure of 1.4×10−4 Torr liter/cm3, this skin would allow diffusion of hydrogen into the ultra-high vacuum system and reduce the charged particle lifetime in the bottle. A representative solution is to surround a primary vacuum region with a second high vacuum system that is pumped, e.g., with a miniature sputter-ion pump. By reducing the concentration of hydrogen, e.g., nine orders of magnitude, the problem of hydrogen diffusion can be minimized or eliminated.
Near the charged particles, a highly aggressive method of removing residual gas molecules can be surface gettering. The electrodes and other conducting surfaces of the bottle can be comprised of titanium, which is a good getter material. Just before filling the bottle with the charged particles, the getter material can be heated to outgas the material and generate clean surfaces capable of adsorbing sufficient numbers of gas molecules to maintain the vacuum for weeks or months.
To fill bottles, the injection of charged particles can be accomplished by first attaching the bottle to an existing charged particle source, such as an ion source or a particle accelerator. A vacuum gate valve can be used to merge the bottle vacuum with the particle source vacuum. The charged particles are then directed toward the bottle. In order to hold the charged particles within the bottle, the electric field (which prevents stored charged particles from again exiting the bottle) can be briefly modified during the incoming passage of the injected charged particles. Briefly reducing the voltages on the electrodes near the bottle entrance can be a modification that enables charged particle injection.
Extraction of charge particles stored in the bottle can occur with a procedure inverse to that used for charged particle injection. Another embodiment is to slowly lower the electrode voltages near the bottle entrance, allowing the stored charged particles to slowly spill out. These extracted charged particles can be directed into a particle accelerator. The extracted charged particles can be used in medical therapies, for isotope detection, for isotope generation, for the induction of nuclear fission or fusion, for imaging, of for catalyzing chemical reactions.
In some embodiments, antiprotons are stored and transported in the bottle. However, there are applications wherein the antiprotons do not need to be extracted, but rather annihilated within the bottle itself. One way to accomplish such annihilation is by injecting a gas into the bottle. The gas can be hydrogen. Byproducts of this antiproton annihilation are secondary particles and rays. Embodiments herein can use these secondary particles in interrogating a shielded container for nuclear materials.
When a source of electrons is added, the properties of the bottle can be improved. First, an ion-sputter pump functionality is created by ionizing the residual air molecules in the vacuum chamber. Second, the electrons cool the charged particles in order to overcome the intrabeam scattering. Third, the electrons create a space-charge counter-force which allows more charged particles to be stored in the electrostatic bottle.
In addition to the use of electrons to control the temperature of the stored charged particles, changes to select electrode voltages based on measured charged particle positions and velocities can also be used to reduce and maintain the temperature of the stored charged particles.
Power can be used to maintain the electrode voltages, maintain the vacuum within the bottle, and implement technologies for maintaining the temperature of the stored charged particles. Batteries can be used to provide sufficient power to operate the bottle without external power. Under some conditions the operational power level can be less than ten Watts.
The apparatus can be used for transporting charged particles, again herein exemplified as including antiprotons. Because vibrations can occur when transporting on a vehicle or a person, steps can be taken to minimize the relative motion of electrodes within the bottle. This minimization of structural deflections is useful at the oscillatory frequencies of the stored charged particles. The vehicles used for transport can include automobiles, trains, aircraft, and rockets.
Representatively, one way of viewing the teachings herein is as an apparatus used in storing and transporting charged particles. The apparatus can include: an electric field within the apparatus capable of preventing or controlling the charged particles from striking a surface within the apparatus; and a means for maintaining a vacuum within the apparatus in the region of the charged particles. In another way of viewing the teachings herein, there can be a method of storing and transporting charged particles. The method can include generating an electric field within a bottle capable of preventing or controlling the charged particles from striking a surface within the bottle; and maintaining a vacuum within the bottle in the region of the charged particles.
Another embodiment can be phrased as an apparatus for storing (and in some cases transporting) antiprotons. The apparatus can include an electric field within the apparatus capable of preventing or limiting the antiprotons from striking the surface within the apparatus;
and a means for maintaining a vacuum within the apparatus in the region of the antiprotons. Yet another embodiment can be articulated as a method of storing and transporting antiprotons, including: generating an electric field within a bottle capable of preventing the antiprotons from striking a surface within the bottle; and maintaining a vacuum within the bottle in the region of the antiprotons.
Representatively, another way of viewing the teachings herein is as an apparatus and/or method of storing charged particles that is devoid of a controllable magnetic field or need therefore. Compare this view with “Container for Transporting Antiprotons,” U.S. Pat. No. 5,977,554 issued to Gerald A. Smith, et al. on Nov. 2, 1999 and “Container for Transporting Antiprotons,” U.S. Pat. No. 6,160,263 issued to Gerald A. Smith, et al. on Dec. 12, 2000. The realization that the magnetic field used in Penning traps is not required leads to important improvements in container weight and size.
Representatively, yet another way of viewing the teachings herein is an apparatus and/or method of storing charged particles that is devoid of a cryogenic temperature, and/or a container with a cold wall, (and associated thermally conductive supports in thermal connection with said cold wall), and/or dewar associated with the container or need therefore. Compare this view with “Container for Transporting Antiprotons,” U.S. Pat. No. 5,977,554 issued to Gerald A. Smith, et al. on Nov. 2, 1999 and “Container for Transporting Antiprotons,” U.S. Pat. No. 6,160,263 issued to Gerald A. Smith, et al. on Dec. 12, 2000. In the teachings herein a vacuum is maintained through any of a number of means, including gettering, ion-sputter pumping, and the employment of an envelope vacuum. The realization that cold walls and cryogenic temperatures used in Penning traps are not required leads to important improvements in container weight and size.
Representatively, yet another way of viewing the teachings herein is as an apparatus and/or method of storing charged particles that is devoid of multiple electric fields or need therefore. Compare this view with “Container for Transporting Antiprotons,” U.S. Pat. No. 5,977,554 issued to Gerald A. Smith, et al. on Nov. 2, 1999 and “Container for Transporting Antiprotons,” U.S. Pat. No. 6,160,263 issued to Gerald A. Smith, et al. on Dec. 12, 2000. In the teachings herein a single electric field, generated by multiple electrodes, can be handled as a single integrated field. The realization that the cryogenic temperatures used in Penning traps is not required leads to important improvements in container weight and size.
Another embodiment can be phrased as an apparatus and/or method of storing and/or transporting antiprotons. These antiprotons are generated when high energy ions strike a target, colliding the ions against the atoms in the target. These collisions cause fragmentation of the ions and atoms, which sometimes re-coalesce in the form of antiprotons. Because of the radiation levels, energy difference between the incident protons and exiting antiprotons, and system complexity of the antiproton capture system, this target is not found within a synchrotron (see, e.g., U.S. Pat. Nos. 5,977,554, 6,160,263, etc.) but rather a separate location within the accelerator complex. These antiprotons can then be decelerated and injected into a portable container. As a prophetic teaching, this portable container with injected antiprotons can be used to generated biomedically useful radioisotopes at the bedside of a patient. Compare this teaching with “Container for Transporting Antiprotons,” U.S. Pat. No. 5,977,554 issued to Gerald A. Smith, et al. on Nov. 2, 1999 and “Container for Transporting Antiprotons,” U.S. Pat. No. 6,160,263 issued to Gerald A. Smith, et al. on Dec. 12, 2000.
If the charged particles 102 that are stored in the bottle come into contact with residual gas molecules within the vacuum maintained in the bottle, they can be lost through chemical, nuclear, or annihilation reactions. In this embodiment a second vacuum system 306 that acts as a protective envelope around the central primary vacuum system 308 can be implemented. This envelope vacuum system 306 prevents atmospheric hydrogen and other gases from inducing charged particle losses. A gate valve 310 can be used to separate these two vacuum systems. The envelope vacuum can be maintained using a miniature ion-sputter pump 312. The high voltage needed to operate the ion-sputter pump 312 can be generated by a high voltage power source 314, which in turn can draw the electrical power it needs from a battery 304. In order to inject or extract charged particles from the bottle, the internal gate valve 310 and an external gate valve 316 can be opened to allow passage of the charged particles. In this embodiment of the invention, the methods of injection and extraction can take place with these gate valve(s) cycling open and closed just long enough to allow passage of the charged particles. Within this embodiment, the apparatus can include a gate valve(s) that are fast acting.
The primary vacuum 308 can be maintained by constructing the electrodes 100 and primary vacuum vessel 318 from a material that getters residual gas molecules. In this embodiment, the material is titanium.
In this embodiment, the bottle is protected from extreme temperature fluctuations and physical shock by an external shield 320 that can be comprised of soft, thermally insulating material. The electrodes should also be mounted such that they are insulated from external vibrations.
In one embodiment, the radial focusing of the charged particles is generated by axisymmetric radial electric fields 400 that are a direct result of a voltage gradient along the axis of the electrodes 100.
The stored charged particles 102 oscillate within the electric field that constrains their motion, such that there are well defined resonant frequencies associated with this motion. Mechanical and electric vibrations and modulations with a non-zero power spectrum near these resonant frequencies can cause these charged particle oscillations to increase in amplitude, which is described as an increase in the charged particle temperature. Different approaches can be used to limit or reverse this temperature rise. In one embodiment, the stored charged particles 102 include electrons which interact with the other stored particles. By continuously replacing hot electrons and allowing thermodynamic interactions between all stored charged particles via Coulomb scattering, the temperature of the stored charged particles can be controlled. In another embodiment, measurement of the oscillatory particle signal on one or more electrodes can be electrically amplified and applied to one or more electrodes to reduce that signal. Continuous application of this procedure can reduce the temperature of stored charged particles, and is called stochastic cooling.
In some embodiments, stored antiprotons 600 are not extracted, but rather annihilated within the bottle itself. One way to accomplish such annihilation is by injecting a gas into the bottle. The gas can be hydrogen. As illustrated in
A container 300 storing charged particles 302 can be used for many applications. Because the charged particle 302 have very low velocities, it is often necessary to extract them from the container 300 and accelerate them in a particle accelerator 700. A preferred embodiment of this invention is to store and transport antiprotons 600 for use in these many applications. As illustrated in
The container 300 storing charged particles can be transported in many ways. As illustrated in
Note that the foregoing is a prophetic teaching and although only a few exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate from this teaching that many modifications are possible, based on the exemplary embodiments and without materially departing from the novel teachings and advantages herein. Accordingly, all such modifications are intended to be included within the scope of the defined by claims. In the claims, means-plus-function claims are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment fastening wooden parts, a nail and a screw may be equivalent structures.
This patent application is a continuation, claiming priority from, and incorporating by reference, the following patent application: “Electrostatic Bottle for Charged Particle Storage,” Ser. No. 60/731,971, filed Oct. 31, 2005.
| Number | Date | Country | |
|---|---|---|---|
| 60731971 | Oct 2005 | US |
