Patent Application
20220287171
The present invention relates to the generation of high-intensity electromagnetic fields, with rapid rise times and which can be distributed on great volume extensions, obtained due to the fast charging of a material hit by a high-intensity and energy laser.
The generation of high-intensity electromagnetic fields, with features which can comprise stationarity over a certain time interval, creation and neutralization in short time, and application on large extensions of volume and area, is a research topic of considerable interest in the international scientific community and with wide possibilities of application.
High-intensity electric fields can be sustained only under vacuum, otherwise the ionization effects of air or other dielectrics create known breakdown phenomena, with the consequent neutralization of the fields which produced them.
Among the various possible applications, a classic use in a general sense of such fields is for the acceleration of charged particles by Coulomb's law.
Specifically, by using “capacitor” structures, i.e., in which the electric field region is delimited by parallel conductive surfaces, often replaced by conductive grids. These structures can be used in a typical acceleration/deceleration diagram of charged particles, where the field is parallel to the preferential direction of acceleration and therefore serves to increase/decrease the speed thereof (see
Such devices are classically applied to accelerated particle beams, whether they are continuous or pulsed, low or high energy.
The use of such structures as “deflectors” (or “Choppers”) is important in a particle accelerator in order to prevent the accelerated particle beam from hitting the target on command, instead directing it towards a “beam-dump”.
Both diagrams in
The diagram is obviously applicable only if the capacitor is already charged when the particle beam passes therethrough, and if it maintains the charge thereof for the entire time the beam passes between the capacitor plates.
This scenario is advantageous if the deflection process occurs statically, and therefore the capacitor can be charged even over long periods. If, on the other hand, the process concerns the consecutive passages of several beams, temporally for example in a periodic manner, there are known difficulties due to the capacitor charge/discharge process, which limit the applicability of the method only to a few cases with low repetition frequency.
Limiting the focus to the classic case of a DC voltage generator charging a capacitor for the moment, the problems are due to the following three factors.
1) Maximum electromotive force of the generator: in order to generate high electric fields E=v/d between the capacitor plates (with “E” electric field, “V” voltage applied and “d” distance between the plates), it is necessary to have generators with high output voltage “V”, with the same distance “d”; this often arises as a strong technological limit.
2) Time constant of the charge-discharge circuit: one of the most delicate parameters, often the bottleneck of the problem. If a Cload capacitor must be charged, it must be done through a suitable network formed for example by a cable, with known characteristic parameters; for example, a classic RG58-Belden cable, has as nominal distributed parameters Cc=77 pF/m, Lc=200 nH/m, Rc=10.8 ohm/km. One meter of cable is already sufficient to add an important charge impedance to the capacitor to be charged. It suffices to say that a classic capacitor with circular plates 10 cm in diameter placed 10 cm away from each other under vacuum, has a Cload capacity=0.7 pF, much lower than that of the cable. The equivalent capacitor seen from the generator is the parallel between the two, i.e., 77.7 pF. In practice, the problem of charging the small Cload capacitor becomes that of charging the large Cc+Cload capacitor. It is therefore necessary to provide a total charge equal to 100 times that which would be necessary to charge only the Cload taken individually, to ensure that the voltage applied thereto—and therefore the relative electric field—is that desired. Furthermore, this situation will only occur when fully operational, i.e., after the end of the transient phase, the duration of which depends on the features of the equivalent RLC model of the network.
3) Maximum current suppliable by the voltage generator. Although the circuit is optimized to overcome the second point, the technological limitation posed by the maximum current which the voltage generator can supply is very important when low charging times are required. This fact affects the application of the method in many cases. To try to overcome this problem, the diagram in
This charging and discharging process is limited by the impedances Z1 and Z2, by the capacitors C1 and C2, by the maximum voltage VCC and by the maximum current which can be supplied by the voltage generator. Currently, deflectors are used which operate with kHz frequency, with very complex circuits, as described in A. Caruso, F. Consoli, G. Gallo, D. Rifuggiato, E. Zappalà, A. Longhitano, M. Di Giacomo, “The LEBT Chopper for the SPIRAL2 Project”, Proceedings of the 2nd International Particle Accelerator Conference (IPAC 2011), 4-9 Sep. 2011, San Sebastian, Spain. ISBN 978-92-9083-366-6.
To solve these problems, especially when working with high-energy beams, advanced methodologies use voltages to be applied to the capacitor which are not constant but sinusoidal, or even with different time profiles. This is true both in the cases historically used for acceleration/deceleration and in the more modern cases of deflection. There are several examples in the sinusoidal accelerators, such as Cyclotrons, Linacs, etc. For Choppers which must operate at high energy, such as the Chopper 500, having a capacitance of 7 pF and present at the Southern National Laboratories of the INFN in Catania, sinusoidal driving signals are used and 170 nC of charge are sufficient to impress high energy, high mass and charge ions (typical energy of tens of MeV, masses even up to 58 amu and charges+19) transverse accelerations adequate for sufficient deflections, as explained in A. Caruso, et al, “Chopper 500 Status Report”, Proceedings of the 17th International conference on Cyclotrons and their Applications, 18-22 Oct. 2004, Tokyo, Japan.
The most performing deflecting structures for high energy ions are those which allow a pseudo-Gaussian voltage pulse to be propagated along a transmission line, with a phase velocity equal to the beta parameter of particle propagation, and perfectly synchronized in time with the passage of the beam. On the basis of this, in the propagation path thereof towards ground the associated charge wave generates, at the point of the transmission line section where it is at a certain instant, a normal electric field in the direction of the beam. This field deflects the beam during propagation, inside the deflecting section consisting of the transmission line itself, due to the time synchronism thereof and to the fact that they are both with the same speed, as explained in:
The above allows to understand the most important technological limitations in order to create an adequate deflecting field in the capacitor. The sudden creation and cancellation of a field in the capacitor requires the rapid charging and discharging thereof, which is difficult to accomplish with voltage generators or even capacitors as in the case in
To create an impulse which propagates along a transmission line as described in the previous documents to Di Giacomo and Consoli, very fast, high-power voltage generators must be used. In general, the fast generation of high electric fields in the desired area requires fast charge accumulation in the same area.
To solve some of these problems, pulsed power systems are used, described for example in:
They generally employ methodologies of several cascaded blocks and provide voltages around tens of kV, with currents of different kA and rise/fall times which are generally around milliseconds, as described in R. Péron, F Bordry, J P. Burnet, F. Boattini, “A 60 MW pulsed power supply for particle accelerator: preliminary test results”, Proceedings of the conference: EPE-PEMC 2010, Ohrid, Republic of Macedonia, September 2010, or even greater as described in the Maffia's document. In some cases, the values can also fall within the range between tens and hundreds of nanoseconds as described in:
However, they are generally very bulky structures as shown in Reisman and Downing, especially when they relate with high voltages and currents, and short times.
Regardless, the pulses generated have rising times which do not fall below ten nanoseconds, especially in terms of the generation of high electric fields.
As known, the most modern particle acceleration approaches employ high-intensity, high-energy pulsed lasers, and therefore the accelerated particles are naturally synchronized with such laser pulses. The post-acceleration and conditioning of these beams therefore requires the absolute synchronization of the previously discussed acceleration-deceleration-deflection apparatuses with the pulse of the same laser, and this is a technological limit which is difficult to solve for the devices used up to now.
It is known that the interaction of a high-intensity laser with a solid target generates a plasma and fast electrons associated therewith, which move away from the target in very short time, as described in Atzeni, S., Meyer-ter-Vehn, J., “The Physics of Inertial Fusion: Beam Plasma Interaction”, Hydrodynamics, Hot Dense Matter (Oxford University Press, 2009), and in Macchi, A., Borghesi, M., Passoni, M., “Ion acceleration by super intense laser-plasma interaction”, Rev. Mod. Phys. 85, 751 (2013).
These electrons create a high-intensity local electric field, capable of accelerating the ions in turn. These ions are much slower than electrons, and therefore globally the target—be it dielectric or conductor—shows a strong positive charge once hit by the laser, which can generally decrease over time.
It has been shown that the presence of such a sudden and high positive charge located at the point of laser-matter interaction can drive an electronic neutralization current through the target support, which is itself connected to the conductive vacuum chamber, as described in:
In the documents T. Toncian, et al “Ultrafast laser-driven microlens to focus and energy-select mega—electron volt protons” Science 312, 410 (2006) and T. Toncian, et al, “Properties of a plasma-based laser-triggered micro-lens”, AIP Adv. 1, 022142 (2011), it has been shown how this charge effect, applied to a cylindrical micro-target, can be used to create a focusing electric field in a structure which acts as a micro-lens for a particle beam accelerated by laser-matter interaction. A patent application has also been deposited on this diagram: M. Borghesi, T. Toncian, “Laser irradiated hollow cylinder serving as a lens for ion beams”, WO 2006/097252 A1.
The present invention relates to the generation of high-intensity electromagnetic fields. This phenomenon is caused by the extraction of electrons from material as a result of the laser-matter interaction, and allows a large amount of electric charge to be obtained thereon in very short time, comparable to the duration of the laser pulse used. This rapid mechanism can be used for the creation of high-intensity electric fields with very steep rising edges even on large volumes of space by exploiting structures similar to capacitors or transmission lines, even allowing to have high fields on structures of the type indicated in series. The connection of this structure to suitable RLC circuits allows to have oscillating fields with features which can be adjusted as needed, by intervening on the values of the circuit elements used. The solution suggested herein shows the versatility thereof for the generation of electromagnetic fields which are 1) stationary with a rapid rise time; 2) high-intensity sinusoidal; 3) traveling wave.
This means using the laser-matter interaction as a source for the generation of high-intensity microwave-radiofrequency electromagnetic fields, which can be used in a wide range of applications, in particular as regards the acceleration/deceleration/deflection/focusing/selection of accelerated charges.
The peculiar and important features of field generation produced by this technique allow the use of the same in a range of further applications which can be very wide and multidisciplinary. In particular, such high-intensity transient electric fields with a wide spatial extension can be used for biological and medical studies when applied to cells, or for the characterization of materials and devices subjected to high transient fields, for general electromagnetic compatibility studies as well as in evolved structures which generate radiations in terahertz.
The present invention relates to a method of generating electromagnetic fields comprising the step of using interaction between a laser source and a target, as the source for generating high-intensity electromagnetic fields, in which a strong positive charge is generated in the target hit by the laser. The target has a structure consisting of at least two discrete objects, of which at least one of the two is a conductor, and in which the target structure is used to obtain the acceleration or deceleration or deflection or focusing or selection of moving charges, or even the whole of more than one of the preceding actions.
In particular, in the method of generating electromagnetic fields according to the present invention, the beam of charged particles on which the electromagnetic fields act, has been accelerated by a laser-matter interaction, which is different from that used to generate the electromagnetic fields, or by methods of accelerating particles, which use principles other than the laser-matter interaction, and thus in which the two processes of pre-acceleration and subsequent processing of the particle beam are completely separate and therefore separately tunable and optimizable.
In particular, the electromagnetic fields generated are almost stationary and with microwave radiofrequency, and the material directly hit by the laser is a dielectric or a conductor.
In various embodiments, the step of introducing adjustable or tunable RLC networks is provided to allow obtaining high-intensity electromagnetic fields, which are stationary with a rapid rise time or with a periodic time trend, or with a traveling wave.
The high-intensity electromagnetic fields generated by the laser-matter interaction have very rapid rise times, and are obtained due to the fast charging of a material of the target hit by a high-intensity and energy laser beam and to the extraction of electrons from the material of the target following the laser-matter interaction.
Furthermore, in various embodiments, there is provided the step of using tunable capacitor or transmission line structures to have electromagnetic fields with uniform and non-uniform spatial distributions.
Furthermore, there is provided the step of using tunable connections with convenient RLC circuits in order to obtain electromagnetic fields, from the aforesaid structures, with adjustable time features by acting on the values of the circuital elements used in said RLC circuits.
In different embodiments, there is provided the step of using the aforesaid structures in cascade in order to obtain electromagnetic fields in each structure, which are synchronized with the other structures, but having an intensity and spatial profile which may be different.
Finally, in some embodiments, there is provided the step of using the fields generated for a set of applications belonging to other fields than those indicated in the preceding claims, such as medicine, biology, studies on materials and devices, electromagnetic compatibility, and generation of terahertz radiation.
Further features and advantages of the invention will become apparent from the following description provided by way of non-limiting example, with the aid of the Figures shown in the accompanying drawings, in which:
The parts according to the present description have been depicted in the drawings, where appropriate, with conventional symbols, showing only those specific details which are pertinent to the understanding of the embodiments of the present invention, so as not to highlight details which will be readily apparent to those skilled in the art, with reference to the description presented herein.
The solution suggested and described here differs from Borghesi's document and Toncian's publications for the reasons set out below.
In the case described in the present application, the structure used is in fact different and consists of at least two discrete elements, which makes it of the “multiply connected” type. In the present case, the structure can be employed in the deflection (instead of focusing, as indicated in the Kar's document) of a particle beam which has been accelerated by a completely separate process. This acceleration can occur by classical methods or by laser-matter interaction. The important thing is that these two processes—acceleration and subsequent deflection—are completely separate and therefore separately tunable and optimizable, unlike in the case of the Kar's publication for the focusing effect.
The deflection method caused by a traveling charge wave of a particle beam accelerated by classical accelerators has already been reported in the literature in the documents to Di Giacomo and Consoli, but in these cases the generation of the charge impulse is carried out by a solid-state voltage generator, with obvious limitations as regards the maximum charge which can be deposited, the duration of the pulse as well as the impossibility of absolute synchronization of the charge pulse with the accelerated particle beam, if the acceleration occurs by laser-matter interaction.
The fields of application of the solution suggested here are: acceleration, deceleration, deflection, focusing, selection of accelerated charges in accelerators and sources of charged particles for scientific-academic-medical purposes, and for all those ranges of medical, biological and study applications, processing and characterization of materials, in order to use them in the electronic, avionics, spatial field . . . . These generated electromagnetic fields can also be effectively used for direct application in the medical, biological field when applied to cells, or for the characterization of materials and devices subjected to high transient fields, for studies of electromagnetic compatibility in general as well as in advanced structures which generate terahertz radiation.
The solution of charging a target due to the interaction with a high-energy laser has already been documented in scientific literature. The generation of electromagnetic fields and the related use of this charging phenomenon in the ways, for the purposes and with the methodologies set out herein is instead completely new, and this makes use of a study carried out through theoretical analysis supported by accurate numerical simulations and experimentation carried out on the generation of high charges on a target hit by the nanosecond pulses of the ABC laser of ENEA in Frascati.
The above description requires experimentation in the laboratory in order to identify the optimal features of the devices described. The suggested method then requires the development of prototypes with suitable parameters, which allow to make the described charge accumulation devices efficient and to produce an easily buildable and low-cost version.
The solution described herein refers to a completely alternative method to that of providing the necessary charge by means of suitable voltage or current generators, or by means of the fast discharge of previously charged capacitors, as in the case in
It is known from the documents to Atzeni and Macchi that the interaction of a high-intensity laser with a solid target generates a plasma and fast electrons associated therewith, which move away from the target in very short time. These electrons create a high-intensity local electric field, capable of accelerating the ions in turn. These ions are much slower than the electrons, and therefore once hit by the laser, the target—be it dielectric or conductor—globally shows a strong positive charge, which can decrease over time in some cases. It has been shown that the presence of such a sudden and high positive charge located at the point of laser-matter interaction can drive an electronic neutralization current through the target support, which is itself connected to the conductive vacuum chamber, as described in the documents to Dubois and Poye. The currents engaged in these cases have also been measured in the order of several kA, as described in:
There have currently been attempts to use these currents to power solenoids, in order to create magnetic fields of around Gigagauss, as shown in Santos, Fujioka, Law, and Tickhonchuk.
Some diagrams consider that this current can be used in order to drive an electromagnetic wave which acts on the same beam of ions which are accelerated by the laser-matter interaction, in order to focus them as described in the Kar's document.
In other cases the electric field obtained from the charging of a target due to the rapid emission of electrons has been used to focus a beam of particles emitted by laser-matter interaction as described in the documents to Toncian and Borghesi.
The solution described herein is a completely complementary structure.
In the diagram in
A classic example of a short circuit of this plate on the conductive surface of the vacuum chamber occurs through the support thereof, which is generally conductive in many laser-matter interaction experiments. The aforementioned neutralization current is thus generated.
As occurs in a classic capacitor, the presence of the plate P2 in the immediate vicinity of the plate P1 causes an opposite-sign induced charge on P2 equal to that accumulated on the plate P1. The response speed of the system depends on the area of P1 and the distance between the two plates P1 and P2. This means that a current of electrons will still flow through the connection towards ground M of the plate P2. For this mechanism to be possible, the weight of the plate P1 must be supported with an adequate non-conductive support and P1 must be adequately far from ground M, with respect to the distance separating it from the plate P2. It is known that the charge accumulated on the plate P1 substantially depends on the features of the interaction between the laser and the plate P1 rather than on the shape thereof, and therefore on the overall conformation of the capacitor. Therefore, by changing the shape and distance of the two parallel plates P1 and P2, it is possible to have fields with profiles which are not necessarily spatially uniform. It is possible to obtain charges of around ten nC for laser pulses with 100 mJ of energy with Full Width Half Maximum (FWHM) of around ten femtoseconds, as described in the documents to Dubois and Poye. But high currents up to several kA have been found experimentally, which flow through the target support even in the case of laser pulses with FWHM of around 300 ps and with energies of several hundred joules, as evidenced in the documents to Krása, Cikhardt, Santos, Fujioka, Law, Tickhonchuk, and
which are the clear indication of a high charge accumulation even in these conditions.
Similar phenomena are at the basis of the generation of so-called “ElectroMagnetic Pulses” (EMPs), transient electromagnetic pulses of high intensity and duration up to hundreds of nanoseconds, which are known in all high-energy laser facilities, and are all the more important as the lasers used are of high energy and intensity, as explained in the documents to Dubois, Poye, and F. Consoli et al, “EMP characterization at PALS on solid target experiments”. This charge accumulation phenomenon is therefore directly correlated to the energy and intensity of the laser being used. Charges of around several μC have been demonstrated in some cases, as described in the documents to Krása and Cikhardt when the laser energies are several hundred joules.
The charge on the plate P1 is generated in times which can even be around hundreds of femtoseconds, depending on the type of laser used, thus guaranteeing very low system response times, which cannot be obtained with the classical methods described above. The same is distributed at high speed over the entire plate P1, and the induction of the charge on P2 is therefore also very fast. So as to verify the functioning of the system thus created, electromagnetic simulations have been developed using CST Particle Studio software.
The simulated structure is that shown in
The plates P1 and P2 are circular, with a thickness of 0.75 mm and a diameter D=2R of 20 cm, spaced apart from each other by a distance d=10 cm.
This structure is indicated as “Structure 1”.
The electron charge is emitted with a Gaussian time profile. In particular, the initial instant of the simulation coincides with the Gaussian maximum, and the mean value thereof is obtained at 0.5 ns, for a total charge of 10 nC. A bunch of electrons are considered with an average energy of 100 keV and an energy spread of 100%, emitted in a cone of 40 degrees, within which the angular emission is uniform. The first signal S1 shown in
In reality, the presence of a further resistive element R, depending on the construction features of the structure, will dampen these oscillations.
The signals S2 and S3 concern points placed more towards the end of the plate with coordinates Ex(−d/2;R;0) and Ex(−d/2;1.5R;0), and the field gradually decreases. It is worth noting that the signal S4 Ex(8d;1.1R;0), although obtained outside the capacitor, is very attenuated with respect to the signal S1, but not zero. This is due to the extended spacing of the plates, which does not allow to completely neutralize the effect of the charge deposited on the plate P1. The signal S5 Ey(0;1.1R;0), represents the electric field value in the direction y and in the coordinate position (0;110 mm;0). It is the component of the electric field parallel to the surface and close to the edge thereof (the plate has a diameter of 200 mm), thus having a much higher intensity than the signal S1: in fact, it is known that the value of the electric field depends on the charge density, which on the edge of the plate is very high. It is also observed that the signal is hardly affected by the oscillations seen for the signal S1. This confirms that once the charge has been deposited on P1 it is stable, while that on P2 is affected by periodic variations due to the fact that part returns to the vacuum chamber through the short circuit, in a set of continuous oscillations, due to the inductive connection with the vacuum chamber, as described above. The possible damping by means of suitable resistors, as previously discussed, will reduce this phenomenon to almost eliminate it.
In this case it is observed that the field is much more intense and uniform inside the capacitor, in the median plane, while it is very attenuated outside the capacitor. In particular, the signal S11 represents the signal in the coordinates Ex(−d/2;0;0), the signal S12 in the coordinates Ex(−d/2;R;0), the signal S13 in the coordinates Ex(−d/2;1.4R;0), the signal S14 in the coordinates Ex(8d;1.1R;0), and finally the signal S15 in the coordinates Ey(0;1.2R;0).
The proximity and extension between the plates P1 and P2 causes a compensation effect of the charges, which intensifies the internal field of the capacitor and reduces the external one. Furthermore, it is observed that the proximity of the two plates P1 and P2 causes the field to oscillate strongly even in the vicinity of the plate P1 (signal S15). Even in this case, the use of suitable resistive dissipators will allow the damping of these oscillations.
The charging times are very short, around 2 ns, and are linked to the conformation of the capacitor, but also to the emission duration of the electrons, considered in this case as an example equal to 0.5 ns.
For interactions with much shorter pulsed lasers (picoseconds or femtoseconds), the rise times are significantly reduced. Once the capacitor charge is obtained, it is possible to provide for the discharge in a simple manner by means of fast switches, which can be used to short-circuit the capacitor plates, using for example spark-gaps as described in the documents:
There are already very rapid spark-gap switches which have the ability to withstand currents of several tens of kA with voltages up to MV and response times of less than 100 ps, as shown by the three previous references. These switches can be activated by laser, which allows a very precise absolute synchronization with the initial laser pulse which had allowed the charge to be deposited on the capacitor. Thereby, on command, electric field pulses with fast rising and falling edges and the possibility of being periodic are obtained, using commercially available pulse train lasers for this purpose.
This method of creating electric fields on regions which can be of high area and volume, obtained by fast charging the plate P1 due to the ejection of electrons because of the laser-matter interaction, can be successfully applied to any type of accelerating-decelerating-deflecting structure of particle beams. As mentioned, this method allows the absolute synchronization of the post-acceleration and deflection process with that of the initial emission, if the latter is also obtained by laser-matter interaction. This synchronization is easily achieved by using the same laser seed to carry out both processes.
It is important to consider the case of a set of capacitors placed in series, the first of which is affected by the present sudden charge accumulation mechanism. In this configuration, once a certain charge is accumulated on the first capacitor, the same will be found in all those in series therewith. However, since the electric field depends on the charge density, according to the law:
E=Q/(S*ε) (1)
(with ε dielectric permittivity, Q accumulated charge and S plate area), it is possible to have, with a single laser shot on the plate of the first capacitor, a succession of structures the field of which has different intensity according to the different area of the plates (see
This methodology so far discussed and applied to the series of capacitors allows to solve a known and important problem. Now suppose we have two capacitors C1 and C2 in series, with capacitance C1>>C2.
If the capacitor C1 was isolated, to charge it with a charge Q1 it would be enough to use a generator which maintains a voltage V1=Q/C1. However, by connecting C2 in series to C1, the series of the two capacitors is in fact an equivalent capacitor with a capacitance Ceq very close to C2.
The voltage generator, applied to the ends of the series of the two capacitors, must charge them simultaneously. With the same charge Q deposited, the voltage Veq applied to the series C1-C2 must be Veq=Q/Ceq≈Q/C2>>V1, i.e., a much higher voltage than in the previous case.
This problem is naturally solved by the configuration in
High intensity laser-matter interaction is known to produce a wide range of radiation. For the described method to be effective, a considerable part of this radiation must not pass through the target being hit. To this end, it is possible that this target (represented here by the electrode P1) is also very thick, and made of a high-density material, such as lead. The most intense laser-matter interactions allow to obtain several hundred MeV of electrons and protons up to 100 MeV.
By properly choosing the material, thickness, and shape of the target P1, these particles can be stopped. The same can be said for X-rays, but it is possible that gamma rays (expected in scenarios with higher laser intensity, up to a few tens of MeV for the type of laser-matter interactions of interest for the project) could be difficult to attenuate or absorb. Since the X-gamma emission spectrum of the laser-matter interaction is strongly decreasing with the energy, the gamma rays energetic enough to pass the protection constituted by P1 will still be in very small numbers, and precisely because they are able to cross P1 they will interact very little with the rest of the structure. We therefore estimate that it is possible to provide an adequate screen for the whole series of capacitors represented by
This expedient allows the use of the method, for example in the biological field, for the application of these fields to live cells, or also to materials and devices, as stated below.
It is an interesting feature that these fields thus generated can be measured with relative ease by using intense electric field probes such as the D-Dot described in the document Edgel, W. R., “Primer on electromagnetic field measurements”, Prodyn Application note, PAN 895, 1-14, or electro-optical probes described in the document F. Consoli et al, “Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime”, Scientific Reports 6, 27889 (2016), and work patterns can be efficiently performed with existing or under-preparation high-powered repetitive lasers.
As previously described, if in the initial diagram in
Instead, the introduction of inductive elements only involves the presence of strong sinusoidal oscillations, in connection with shorter rise times however. The introduction of tunable elements in this connection towards ground therefore allows to obtain the rise time performance of the electrostatic fields or the amplitude and frequency of any sinusoidal oscillations which can be changed as needed.
Thereby, the structure can be used to supply an electrostatic field with rapid creation/destruction or can be a sinusoidal oscillator with a high amplitude and appropriate frequency, in a manageable manner with relative ease.
A further use diagram of the methodology concerns the creation of charge pulses with a short time duration, which propagate as waves along a suitable transmission line, as in the diagram in
The laser hits the plate P1, connected to a transmission line closed in the characteristic impedance thereof. Thereby, the bunch of charge Q1 which is created on the plate P1 propagates in the form of a pseudo-Gaussian pulse towards the end of the transmission line. At a certain instant, the bunch of charges Q1 will be in a particular point of the transmission line, and an associated electric field will be located there.
This is the principle of the advanced traveling wave deflection diagram of the High Energy Accelerated Particle Chopper, built for the Linac Spiral 2 in Ganil (France) and described in the documents Di Giacomo, Consoli “RF design of the power coupler for the SPIRAL2 Single Bunch Selector” and Consoli “Broadband electromagnetic characterization of a 100 ohm traveling-wave electrode by measuring scattering parameters”. In fact, if a second bunch of high-energy charged particles Q2 travels parallel to the transmission line (shown in
1) the transmission line is formed so as to have the phase velocity of the electromagnetic wave associated with the bunch P1 equal to the drift velocity of the bunch Q2, and
2) the two bunches are time synchronized,
then the field due to the bunch Q1 will be temporally synchronized with the bunch Q2 for the whole duration of the propagation of both along the transmission line. The field generated by Q1 will therefore affect Q2 for the entire crossing of the transmission line, deflecting Q2 in the meantime which moves therein. This technique is particularly efficient for high-energy Q2 bunches, where the classic capacitor deflector is not sufficiently effective. The difficulty, however, is to have bunches Q1 of high charge, short duration and periodically available. All features easily obtainable if this charge is obtained by the laser-matter interaction process described above.
Thereby, the described solution shows the versatility thereof for the generation of high-intensity electromagnetic fields which are
This means using the laser-matter interaction as a source for the generation of high-intensity microwave-radiofrequency electromagnetic fields.
As applications, in addition to the acceleration/deceleration/deflection of particles in accelerators, this methodology can also be used in electrostatic spectrometers, where capacitor structures are used for energy selection. This means being able to activate or not activate an electrostatic spectrometer on command and at very fast times, as well as in a repetitive manner. Furthermore, if the generated charge is sent to a classic electrostatic lens structure, it is possible to obtain the focusing of a beam of charged particles as described in Szilagyi, M. “Electron and ion optics” (Plenum Press, 1988).
The peculiar and important features of field generation produced by this technique allow the use of the same in a range of further applications which can be very wide and multidisciplinary. In particular, such high-intensity transient electric fields with a wide spatial extension can be used for biological and medical studies when applied to cells, as illustrated in the document Pakhomov, A. G., Miklavčič D., Markov M. S., edts., “Advanced electroporation techniques in biology and medicine” (CRC Press, 2017), or for the characterization of materials and devices subjected to high transient fields as described in
Of course, without prejudice to the principle of the invention, the construction details and the embodiments may widely vary with respect to the above description given by way of a mere example, without departing from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019000014385 | Aug 2019 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/057464 | 8/7/2020 | WO |
