US3155593A

US3155593A - Apparatus for producing neutrons by collisions between ions

Info

Publication number: US3155593A
Application number: US3361A
Authority: US
Inventors: Robert R Warnecke; Leboutet Hubert
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1959-02-02
Filing date: 1960-01-19
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03
Also published as: FR1226493A

Description

1964 R. R. WARNECKE ETAL 3,155,593

APPARATUS FOR PRODUCING NEUTRONS BY COLLISIONS BETWEEN IONS Filed Jan. 19, 1960 2 Sheets-Sheet 1 IIIMII I INVENTORS Ruben R. wARMe'c/rE'e/ (\I H- LE'BOUTET.v BY Z7 flaw ATTORNEY 1964 R. R. WARNECKE ETAL 3,155,593

APPARATUS FOR PRODUCING NEUTRONS BY COLLISIONS BETWEEN IONS Robe/1 R- WAR/VFCKE e/ H- LEBUUTET BY 9 W ATTORNEY rates The present invention relates to an apparatus for producing neutrons, and more particularly relates to an apparatus operative to produce an intense and continuous flow of neutrons by fusion of atoms of suitable ion particles within an evacuated enclosure or vessel in which impacts or collisions of the ion particles are rigorously controlled to enhance the probability of nuclear fusion.

It is known that upon the occurrence of an impact or collision between two ions of relatively light-weight elements having appropriate energies, there exists the probability of nuclear fusion accompanied by the emission of a flow of neutrons. Reactions of this type are likely to takeplace in particular between the deutons or the tritons, or between two deutons with the production of tritons in an intermediate reaction. This principle has been utilized primarily in devices in which the collisions between ions have been produced within the center of a plasma, that is, within an electrically neutral environment composed of ions and free electrons. However, energy considerations have shown that the presence of electrons is harmful in this case to the conservation as well of the total energy as of the ions within the interaction zone. Consequently, the devices in question of the prior art had only a slight probability of reaction and a very weak output.

It has already been proposed to obtain neutrons by collisions of two ion beams, i.e., by collisions between ions within an ionic surrounding or environment as pure as possible which contains electrons only in relatively reduced quantity such that the effect of the impacts on the electrons is at the most of the same order of magnitude as the effect of the impacts on the ions. posal has failed in the prior art devices, principally because it has been noted that the ion density within the beams in collision was much too weak to provide densities of a power offering a practical interest.

The principal object of the present invention is a device for producing neutrons by collision of ions in an ionic surrounding in which the probability of reaction, and, therefore, the continuous flow of neutrons is increased as compared to the known prior art devices both by'an increase of the ion density within the interaction zone as by an increase of the duration of the stay or presence of the ions within this zone with a predetermined energy.

The increase in ion density is obtained according to the present invention by making the ion beam circulate in the form of a chaplet of bunches.

The increase of the duration of stay of the ions within the interaction space is obtained according to the present invention by imparting to the bunches a to and fro movement in such a manner that there are periodic encounters between the bunches going in opposite directions in one or several fixed predetermined zones of collision.

Preferably, a single ion source is utilized in the present invention in such a manner that the bunches, after having traversed the initial trajectory, constitute themselves the bunches of the return trajectory upon appropriate reflection thereof.

The forming or grouping of the ions into bunches may be eifectuated in accordance with the present invention either already at the ion source itself or within the opera- However, this pro- Patented Nov. 3, i964 EQQ tive portion of the apparatus by means analogous to those used in velocity-modulated tubes, or in the further alternative, by combining these two aforementioned arrangements in one apparatus.

Consequently, the device according to the present invention is constituted essentially by an evacuated enclosure or vessel, by suitable means for injecting into this enclosure ions of a relatively light-Weight element or elements, and by means to group these ions into bunches, the enclosure or vessel itself including a space devoid of any electric field, to be referred to hereinafter as drift space, in which the bunches of ions move with a constant velocity along substantially the same path or trajectory, and a reflector space located at each of the two ends of the drift space in which exists a high electric field, each of these reflector spaces being defined or limited by an electric mirror carried at a potential very much higher than that of the drift space, the ion bunches are thereby subjected to a constant acceleration within these reflector spaces which initially brakes the same until they attain zero speed, thereupon forces the same to change direction, reaccelerates the same until they have the same energy as they possessed previously within the drift space, and thereafter reinjects the same into the drift space.

The device according to the present invention is additionally characterized by the fact that an axial magnetic field of predetermined intensity is applied to the space of circulation of the ions, and that the various elements of the system, included therein the energy of the ions, the parameters of the bunch-forming means, the voltages and the distances of the electrodes of the system are chosen as a function of the ionic current density and of the output of the desired neutrons in such a predetermined manner that the ion beam is maintained in a stable manner near the axis of the system notwithstanding the significant spacecharge forces, and that each particle the speed of which or position of which has been changed in the course of an impact is returned toward its normal trajectory if the deviation suifered by the particular particle with respect to phase and speed is not too great.

The apparatus dimensioned in such a manner according to the present invention exhibits the property that each given dimension corresponds to one and only one level of energy of the ions which thereby find themselves in a stable state of beam effectuating a continuously identical to and fro movement; it follows therefrom that to the extent the injection of the gas proceeds, there accumulates within the system an ever increasing number of charges which acquire the energy in question, and that it is with this well determined energy that the particles remain within the enclosure or vessel during a relatively very long time.

Accordingly, it is an object of the present invention to provide a simple apparatus for producing a relatively large amount of neutrons in a reliable and continuous manner.

Another object of the present invention is the provision of a neutron producing device which is relatively simple in structure, reliable in operation and which obviates the disadvantages encountered in the prior art devices.

Still another object of the present invention resides in the provision of a neutron source in which the ions are formed into a chaplet of ion bunches continuously moving to and fro within a predetermined space thereby increasing the ion density and therewith the probability of a nuclear fusion.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, two embodiments in accordance with the present invention and wherein:

FIGURE 1 is a longitudinal, axial cross-sectional view through a first embodiment of a neutron producing device in accordance with the present invention utilizing velocitymodulation and drift for grouping the ions into bunches, and

FIGURE 2 is a longitudinal, axial cross-sectional view through a modified embodiment of a neutron source in accordance with the present invention in which the ions are cutup into bunches right at the ion source thereof.

Referring now the the drawing wherein like reference numerals are used throughout the two views to designate corresponding parts, and more particularly to FIGURE 1, the apparatus indicated therein in axial cross-sectional view includes a metallic cylinder 1 forming the drift space. The drift space formed within metallic cylinder 1 is located between two capacitive spaces 13 and 14 of which the axial dimensionis assumed to be negligible. The distance between these spaces is indicated in the drawing by dimension L. The space 13 is in communication through an aperture 29 with a space 30 in which is disposed an electrode 10 of any suitable construction, analogous to a reflector electrode in a reflex klystron and carried at a relatively high positive potential V for example, at 50 or 100 kv. which may also be adjustable in any suitable manner with respect to the potential of the metallic cylinder 1. The potential V is provided by a power supply or voltage source 12. The evacuated enclosure or vessel is limited by vacuum-tight windows in the form of insulating cylinders 5, and by an insulating cover 26 through which passes a tubular member connected permanently to a vacuum pump 2 of suitable construction and capable of maintaining a vacuum of the order of torr.

On the opposite side of the device, the space 14 is in communication through an aperture 31 with a space 32 in which is located the discharge orifice of an ion injector, carried by means of source 12 essentially at the same voltage as the reflector 10. A cylindrical electrode 11 carried at a positive voltage with respect to the orifice 15 is also located within the space 32 for the purpose of providing and forming ahead of the orifice 15 an equipotential surface 33. The voltages and the geometry of the electrodes described hereinabove are such that the surface 33 has the same distance from the transverse plane of symmetry 8 of the device as the surface 42 corresponding to the same potential as the surface 33 and formed in front of the reflector 10. The distance between the capacitive space 13 and the reflector 10, on the one hand, and the distance between the space 14 andthe surface 33 is indicated by dimension D. The evacuated enclosure or vessel is completed at the right hand end thereof, as viewed in FIGURE 1, by an insulating disk 34 and by a glass part 25.

A high-frequency electric field of frequency f, suitably chosen in accordance with the laws and formulae to be indicated hereinafter, is excited at the ends of the spaces 13 and 14. The excitation of this high-frequency field f may be obtained by any suitable means, however; I

in the embodiment of FIGURE 1, rhumb'at'ron-type sayities 3 and 4 are used for that purpose .of-which the capacitive spaces are combined with the spaces 13 and 14. At the interior thereof, the cavities 3 and 4 are each loaded by means of an assembly of annular ferrite mernbers 24, forming a core in which the magnetic flux is.

energized by a respective primary winding 27 or 27'. The two windings27 and 27 of the cavities 3 and 4 are energizedin phase opposition by means of. connections 28 from the same high frequency generator 6.

The ion source may be of any known type, however, for purposes of illustration thereof for use with the present invention, a high-frequency ionization device has been illustrated as a representative example. This field is provided from a generator 16 energizing a winding 1'7 disposed about the glass portion 25. The gas, for example, deuterium, is supplied through a tubular member 18,

and a slight pressure, of the order of 10- torr, is maintained on the inside of the glass portion 25 by means of any suitable vacuum pump (not illustrated herein) connected therewith through the tubular member 35. Means for adjusting the discharge are provided at 19. The tubular member 18, disposed coaxial with the axis of the enclosure or vessel 1, discharges into the glass portion 25 and supports thereon an electrode 20, carried by means of source 21 at a suitable but positive potential, for example, of the order of 2 kv., with respect to the electrode of the orifice 15. A diaphragm 23 is also disposed within the orifice 15 which is intended to constrict the intercommunication between the space under low pressure within the glass portion 25 and the space within the remainder of the enclosure or vessel maintained under a higher vacuum.

An axial magnetic field B, of which the intensity is suitably calculated, is established on the inside of the enclosure 1 by means of electromagnetic windings 7 surrounding the enclosure 1. In the embodiment illustrated in FIGURE 1, there are only two windings 7 disposed to provide within the region of the plane of symmetry 8 a free space 9 which serves for the exploitation of the neutron beam.

Operation The operation of the device illustrated in FIGURE 1 is as follows:

The deuterium gas, supplied through the tube 18 is ionized under the influence of the high-frequency field produced by the windings 17, and the electrode 20 captures the free electrons whereas it repels the ions which are extracted through the diaphragm 23 and the orifice 15. The ion beam which entersthe enclosure orvessel 1 effectuates, under certain given conditions of the various dimensions which will be explained more fully hereinafter, a to and fro movement which is both stable and continuous by traversing at first the space of length D between the surface 33 and the capacitive space 14, referred to hereinafter as the reflector space, thereupon the high-frequency field within the space 14, thereupon the space of length L between the spaces 14 and 13, to be referred to hereinafter as drift space, thereupon the highfrequency field of the space 13, and thereafter by entering into the reflector space between the capacitive space 13 and the electrode 10. Prior to arriving at the electrode 10, the ions are repelled as a result of the positive potential thereof and, therefore, resume their original path in the opposite direction, traversing again the capacitive space 13, the drift space, and the capacitive space 14, and thereafter entering the reflector space between space 14 and equipotential surface 33. Prior to reaching the equipotential surface 33, the ions are repelled and thereby returned upon themselves as by electrode 10 and, as a result thereof, resume the original path in the'opposite direction whereby the movement of the ion beam recommences cyclically in the manner described hereinabove.

' At the end of repeated passages through the high-frequency fields in spaces 13 and 14, the ion beam will be,

cut up into bunches. For an appropriate dimension of the system, the bunches of the ion beam which move in one direction and those of the beam which return in the opposite direction meet periodically always at the same points of the space, these points corresponding to the region of the plane of symmetry 8 and eventually to the region of one or several planes equidistantly situated on either side of the plane of symmetry 8. These encounters lead to impacts or collisions between deutons which in turn give rise to a flow of neutrons and protons intermixed according to the reactions of fusion well known in nuclear physics. The neutrons traverse easily the walls of the enclosure or vessel 1 if they are liberated or freed within the neighborhood of the regions of collisions or impacts. In contrast thereto, protons are captured by the walls maintained at a negative potential with respect to the potential indicative of the energy thereof. The residual helium ions obtained in these reactions are evacuated by the pump 2 which thereby makes room for the admission of a beam of fresh deutons furnished by the gun.

The equations and laws for the dimensions established according to calculations of applicants which satisfy the conditions of stability of the ion beam and the generic subordination of the energy level to this dimension will now be set forth in detail:

By taking a desired energy level of ions, expressed by the voltage V which is as high as possible but has to be slightly less than the voltage V one may select the density of the ion current I and thereafter calculate the magnetic field B, or vice versa, by utilizing the following equation:

in which a is the effective section of fusion of two deutons,

e is the elementary charge of an electron or proton, and p is the number of planes of encounters of bunches.

For the arrangement of the embodiment of FIGURE 1, it has been assumed that 17:1.

The length of the drift space L may be calculated, if the values for V and f are known, from the following equation:

[2e W em. l

in which V is in units corresponding to those of the system in which the values of eand M are expressed,

f is in cycles/ second,

M is the mass of a deuton=2 1836 the mass of an electron, and

k is an integer number:

Zvhich in the embodiment of FIGURE 1 means p=1, Tlie length of the reflector space D is then given by the following equation:

L V cm.' 1

in which k is a second integer number; in the embodiment of FIGURE 1, it has been assumed that k 1: k p. I

The particular selection k1=k implies in fact the existence of a single bunch along the initial trajectory or to movement of the beam and also of a single bunch only along the return trajectory or fro movement of the beam, and, only a single encounter of the bunches within the plane of symmetry 8 of the device. However, it may be readily verified that the relations indicated hereinabove between L, D and f correspond to the choice of frequency 7 equal to a multiple of the inverse of the time of a simple trajectory or path of a bunch from one end to the other of the system.

The means for cutting the ion beam into bunches, constituted in FIGURE 1 by the means comprising the generator 6, the cavities 3 and 4 and the capacitive spaces 13 and 14 have only been illustrated in connection with this embodiment for exemplary purposes. However, it is understood that any other suitable means may be provided in their place, particularly including means to cut-up the ion beam into bunches already at the source thereof.

FIGURE 2 illustrates a modified embodiment in accordance with the present invention which utilizes such a variation. At the same time, it has been assumed in this embodiment that the dimensions selected therefor are such that no longer a single plane exists but that instead, for example, five equidistant planes exist including therein the plane of symmetry 8 of FIGURE 1 which are intended for the encounters of the bunches. Consequently, in the embodiment of FIGURE 2 it has been assumed that p=5 and k '=3.

FIGURE 2, in which the same reference numerals are used to designate corresponding parts, differs essentially from FIGURE 1 in that the capacitive spaces 13 and 14 of FIGURE 1 are omitted in FIGURE 2 and that the drift space disposed in the inside of cylinder 1 which, in the embodiment of FIGURE 2, is made, for example, of insulatingmaterial having

metallic pieces

36 and 37 secured thereto at the ends thereof, is disposed directly between the

refiector spaces

30 and 32. The electrode 10 is disposed in FIGURE 2 within a glass portion 38. The ion source 15, together with the tubular inlet member 18 for the gas and the tubular member 35 for the pump may be of any suitable type and construction as known in the prior art. Only, for purposes of cutting the ion beam into bunches, a diaphragm member 39 is located in front of the diaphragm 23, the latter playing the same role in FIGURE 2 as in FIGURE 1; the diagraphm member 39 is thereby normally held at a positive voltage with respect to the electrode 15 by means of voltage source 41 but is also adapted to be polarized from a source of pulses 49. The diaphragm member 39 thereby normally blocks the passage of ions but permits the passage of a bunch of ions when a negative pulse applied thereto from pulse source 40 temporarily brings the same to the potential of the electrode 15. The repetition frequency of the pulses of the source 40 is chosen in accordance with the same rules and laws as applicable to the frequency of generator 6 of FIGURE 1, that is, it must be a multiple of the inverse of time of a simple trajectory of an ion bunch from one end to the other of the system.

The cylinder 11 plays the same role in FIGURE 2 as played in FIGURE 1, namely to form .an equipotential surface 33 intended to reflect the ions when they return toward the source after having effectuated a to and fro trajectory.

Having assumed p=5, not only two but six energizing windings 7 are shown in FIGURE 2 which are disposed on either side of each of the equidistant planes including the plane of symmetry 8 and the supplementary planes of symmetry b. Consequently, there are created by this arrangement five regions 9 for the escape of neutrons as indicated in FIGURE 2.

It should also be noted that there are no differences between FIGURES 1 and 2 from the point of view of functioning nor from the point of view of rules of dimensioning which all conform to the relations and equations of general nature indicated hereinabove.

It is also understood that in the case in which it is desirable to produce impacts between ions of two different gases, for example, deuterium and tritium, the left hand reflector as seen in FIGURES 1 and 2 may be replaced by a second injector analogous to that of the right hand side thereof, provided appropriate modifications in the dimensions of the electrical and geometric dimensions of the system are also made.

The ion gun represented schematically in FIGURE 2 may be of any suitable known construction utilizing any known principle such as, for example, ionization by an electron beam, by an electric arc, by cold emission and the like. It is also understood that all of these different types of ion guns may also be used in connection with FIGURE 1 without departing from the spirit of the pres ent invention. Similarly, the actual construction of ion mirrors, either actual or virtual, is susceptible, with respect to the constructions indicated hereinabove of numerous modifications which do not affect the essence of the present invention. The means described for forming the bunches may be replaced by any other equivalent means known in the prior art, and the system of energizing the high frequency field may be realized in any appropriate form, depending on the order of magnitude of the frequencies utilized.

While we have shown and described two specific embodiments in accordance with the present invention, it is understood that the present invention is not limited thereto but is susceptible of many changes and modifications within the spirit and scope of the present invention. This is true of all the auxiliary devices utilized to bring about the desired results which have been described hereinabove only for purposes of illustration of the present invention though the broad principles of the present invention may be realized by any suitable means other than those specifically indicated hereinabove. Consequently, while we have shown only two specific embodiments of the present invention, it is understood that the same is not to be considered limited thereto but includes all those changes and modifications, without departing from the spirit and scope of the present invention, as are within the scope of a person skilled in the art, and we, therefore, do not wish to be limited to the particular embodiments described and illustrated herein but intend to cover all such changes and modifications thereof as are encompassed by the scope of the appended claims.

We claim:

1. A particle producing apparatus for producing neutrons by the impact of ions within an evacuated enclosure, comprising means for effectively producing a continuous to and fro movement of ion beams within said enclosure including means for bunching and effectively reflecting said ion beams in such a manner that periodic encounters between bunches moving in opposite directions are established within at least one predetermined zone, and means for enabling the escape of neutrons produced by impacts between ions of respective bunches moving in opposite directions.

2. A particle generating device for producing neutrons by the impact of ions within an essentially ionic surrounding provided within an evacuated enclosure, comprising means for effectively producing a flow of ion beams within said enclosure in the form of a chaplet of ion bunches, means for imparting to said bunches a to and fro movement in such a manner that periodic encounters between bunches moving in opposite directions are produced within at least one predetermined zone including reflecting means for reflecting said ion bunches in said to and fro movements, and means for enabling the escape of neutrons produced by impacts between ions of bunches moving in opposite directions.

3. A particle generating device for producing neutrons according to claim 2, wherein said means for effectively producing a flow of ion beams within said enclosure in the form of a chaplet of ion bunches includes means for velocity-modulating the ion beam to produce said bunches.

4. A particle gene-rating device for producing neutrons according to claim 2, wherein said means for effectively producing a flow of ion beams within said enclosure in the form of a chaplet of ion bunches includes means for cutting the ion beam into bunches at the ion source of said device.

5. A particle generating device according to claim 4, wherein said means for effectively producing a flow of ion beams within said enclosure in the form of a chaplet of 5 ion bunches includes means for cutting the ion beam at the ion source thereof and means for velocity-modulating the ion beam within said enclosure.

6. A particle generating device for producing neutrons according to claim 2, wherein a plurality of said zones are established within said enclosure.

7. A particle generating device according to claim 2, wherein said first-mentioned means includes a single ion source cooperating with said reflecting means in such a manner that the ion bunches after having effected the initial to movement thereof constitute the ion bunches of the fro movement after reflection by said reflecting means.

8. An apparatus for producing neutrons by the impacts of ions within an evacuated enclosure, comprising means for injecting into said evacuated enclosure ions of at least one relatively light element including means for bunching said ions, said evacuated enclosure including a drift space portion essentially devoid of any elec tric field in which .the ion bunches move with an essentially constant speed along essentially the same path, means for imparting to said bunches a to and fro movement in such a manner that there are produced periodic encounters between bunches moving in opposite direc, tions within at least one predetermined zone, a reflector space portion at each end of said drift space portion, means for establishing a relatively high electric field in each of said reflector space portions, and means for enabling the escape of neutrons produced by impacts between ions of bunches moving in opposite directions.

9. An apparatus for producing neutrons according to claim 8, wherein each of said reflector space portions includes electric mirror means effectively delimiting a respective reflector space portion and carried at a much higher potential than that of said drift space portion.

10. An apparatus for producing neutrons according to claim 9, further comprising means for producing an axial magnetic field for focusing said ion bunches in the to and fro movements thereof.

11. An apparatus for producing neutrons according to claim 10, wherein the ion energy V, the ion current density I, and the axial magnetic field B essentially satisfy the equation of em. 1M T l where V is expressed in units corresponding to the system used with e and M, f is in cycles per second, M is the mass of the ion particle, and k is an integer equal to p being the number of said encounters.

13. An apparatus for producing neutrons according to claim 12, wherein the length D of each reflector space portion essentially satisfies the equation of -2 n kl where k is also an integer and V is the potenial of said mirror means.

14. An apparatus for producing neutrons according to claim 13, wherein the value of f is chosen in accordance with the equation where a is the efiective fusion section of two ion particles, e is the elementary charge of one of the two consisting of electron and proton, p is the number of planes of encounters of bunches, and N is the number of neutrons produced per second and per cm.

15. A devicefor producing an intense neutron flow by fusion of atoms of particles within an evacuated enclosure in which the impacts of said particles take place within an essentially ionic environment, comprising means for producing a flow of ion beams within said enclosure in the form of bunches, means for imparting to said bunches a to and fro movement in such a manner that there are established periodic encounters between bunches moving in opposite directions within at least one predetermined zone including means for producing equipotential reflecting surfaces at the ends of said to and fro movements to thereby reflect said ion bunches, and means for enabling the escape of neutrons produced by impacts between ions of bunches moving in opposite directions.

16. A device according to claim 15, wherein said means for producing a flow of ion beams within said enclosure in the form of bunches includes an ion source, and means at said source for cutting the ion beam into bunches.

17. A device according to claim 15, wherein said enclosure includes a drift space, and wherein said mean-s for producing a flow of ion beams within said enclosure in the form of bunches includes means for velocity-modulating the ion beams.

18. A device according to claim 17, wherein said ion 10 source is a single ion source supplying the ions for both said to and fro movements in said device.

19. A particle-producing apparatus for producing neutrons by the impact of ions within an evacuated enclosure, comprising means for efiectively producing a continuous to and fro movement of ion beams within said enclosure including means for bunching said ion beams in such a manner that periodic encounters between bunches moving in opposite directions are estab lished within at least one predetermined zone, and means for enabling the escape of neutrons produced by impacts between ions of respective bunches moving in opposite directions, the relationship between the ion energy V, the ion current density I and the magnetic field B forming part of said first-mentioned means substantially satisfying the equation of where V is in kilovolts, I in amperes/crn. and B in webers/rrfl.

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