FR2632804A1 - ELECTROSTATIC PARTICLE ACCELERATOR, OPERATING IN PULSE CONDITIONS - Google Patents

Abstract

The invention comprises means 16, 18 for producing particles, an accelerating electrode 8 brought to a high pulse voltage V relative to another electrode 2 pierced to allow the passage of particles accelerated due to the voltage V, and means to bring the accelerator electrode to voltage V, which have n + 1 superimposed conductive elements R1, ..., Rn + 1, isolated from each other, with n greater than 1. The accelerator electrode and the other electrode are respectively connected to the element of rank n + 1 and to the element of rank 1. Ferromagnetic cores F1, ..., Fn-1 are placed in the intervals defined by the elements of rank 1 to n. Coaxial cable windings on each core are designed to bring the element of rank n + 1 to voltage V from voltage V / n. Application to the acceleration of electrons.

Description

- 2632804

  ELECTROSTATIC PARTICLE ACCELERATOR, A

  IMPULSE RUNNING

DESCRIPTION

  The present invention relates to an electrostatic particle accelerator operating in pulse mode, that is to say an electrostatic accelerator whose accelerating voltage is established only. during a weak

  fraction of time, in the form of recurrent pulses.

  This fairly recent technique has the essential advantage of reducing the breakdown risk both in the voltage generator and in the acceleration gap (or "acceleration gap" according to English terminology) of such accelerators. The technique in question is currently used in accelerator injectors. induction, especially in the United States

  of America in the National Laboratory of Livermore.

  The accelerator which is the subject of the invention is part of the family of so-called "low energy" accelerators, that is to say accelerators capable of communicating to the particles that they accelerate energies included in a field ranging from about

100keV up to a few MeV.

  The present invention finds particular applications in various fields of research in physics, which require particles, electrons for example, accelerated to such energy, as well as in the fields of ion implantation and irradiation by electrons or X-rays, the latter being created by braking, in a target

  heavy, electrons accelerated by the invention.

  We already know accelerators

2 2632804

  electrostatics of charged particles, operating in pulse mode, in which the pulse voltage applied to the acceleration interval is obtained by means of a fractional-core transformer. The secondary circuit of this transformer has only one turn, is connected to the electrodes allowing acceleration of the particles and embraces the flow of nl ferromagnetic cores whose primary circuits, also comprising only one turn, are each attacked by a voltage pulse V1. In this way, the tension that we get

  across the secondary circuit is nlxV1.

  These known accelerators have a drawback l.a quantity of ferromagnetic material necessary for their realization is very large o high cost, significant magnetic losses and a

  excessive space for these accelerators.

  The object of the present invention is to remedy this drawback by proposing an electrostatic accelerator operating in impulse regime which, for equal performance, requires a lesser amount of ferromagnetic material than

  known accelerators mentioned above.

  Specifically, the subject of the present invention is an electrostatic accelerator of charged particles, operating in pulse mode, comprising: - means for producing said particles, - at least two electrodes which are provided for the acceleration of these particles, L one of the electrodes, called the accelerating electrode, being intended to be brought, with respect to the other electrode, to a high impulse voltage V capable of creating between the electrodes an electric field which accelerates the particles, said other electrode being pierced for allow the passage of accelerated particles, and - means for bringing the accelerating electrode to high pulse voltage, this accelerator being characterized in that the means for bringing the accelerating electrode to high pulse voltage include: - a set of n + l superimposed electrically conductive elements which are electrically isolated from each other, this assembly thus having in one end of an element of rank 1 -and- at its other end an element of rank n + 1, n being an integer at least equal to 2, the accelerating electrode being electrically connected to the element of rank n + 1 and said other electrode being electrically connected to the element - of rank 1, - at least n-1 ferromagnetic cores, the n-1 cores being respectively placed in the n-1 intervals defined by the elements of ranks I to n, and - at minus one-Electric line, said electric line comprising n-1 windings of N turns of coaxial cable in the same direction, respectively around said n-1 ferromagnetic cores and being designed to bring the element of rank n + l to high impulse voltage V by means of a starting impulse voltage equal to V / n, increasing by V / n this starting voltage at each of said n-1 intervals from the first of these, N being a number

greater than 1.

  The fact of using windings of N turns, N being a number greater than 1, allows the use of ferromagnetic cores of smaller cross section than that of the cores used in the known accelerators mentioned above, and

4 2632804

  therefore the use of a lesser amount of ferromagnetic material than in these known accelerators. In the present invention, this quantity can even be reduced by an important factor, of the order of 3 to 10, compared to that which would be necessary, to

  performance-equal, in these known accelerators.

  According to a first particular embodiment of the accelerator which is the subject of the invention, this accelerator comprises n electrical lines respectively constituted by n coaxial targets, for any integer p greater than or equal to 2 and less than or equal to n, the target of rank p makes said N turns on each nucleus of rank less than or equal to p-1, for any whole number k greater than or equal to 1 and less than or equal to n, the braid and the core of the target exit end coaxial of rank k are respectively electrically connected to the element of rank k and to the element of rank k + 1, the voltage V / n being applied between the core and the braid of the input end of each of these coaxial cables of rank k, each winding is electrically isolated from the elements between which it is placed and the length of each cable and the moment of application of the voltage V / n to each cable are such that the voltages V / n arrive

  simultaneously at the cable outlet ends.

  According to a second particular embodiment, which allows the reduction in the number of windings to be wound on the cores compared to the first particular embodiment, the power line is unique and comprises n sections of coaxial cable of the same length, the sections of rows 2 to n respectively have the n-1 windings, pou, any whole number p greater than or equal to 2 and less than or equal to n, the braid of the entry end of the section of row p is electrically connected to the braid se5 'a2632804 from the exit end of the section of rank p-1 as well as to the element of rank p-1 while the core of the entry end of the section of rank p is electrically connected - -the core of the outlet end of the section of rank p-1 as well as to the element of rank p, the voltage V / n is applied between the core and the braid of the inlet end of the section of row 1, The braid and the core of the outlet end of the section of row n

  are respectively electrically connected to the Element.

  of row n and to the element of row n + 1l and each winding is electrically isolated from the elements between

which ones it is placed.

  In a particular embodiment of the invention, the electrodes are located opposite L5 'element of rank 1 such that the accelerating electrode is included between the latter and said other electrode, the elements of ranks I to n respectively comprise n coaxial holes, Said other electrode is tightly connected around its periphery to the element of rank 1, each element is tightly connected to the element of rank immediately above by a waterproof and electrically insulating ring which surrounds the holes of these two elements and the accelerating electrode is electrically connected to the element of rank n + l by an electrical conductor which

cross the n holes.

  In a preferred embodiment of the invention, the elements of rank 1 to n respectively comprise n other coaxial holes provided for the passage of said line, the n-1 ferromagnetic cores are annular - and coaxial and the axis common to the cores and lfaxe common

  said other holes are confused.

  Preferably, the axis common to the nuclei and

  the axis common to said holes are parallel.

  In a particular realization of

6 2632804

  the accelerator object of the invention, it further comprises a ferromagnetic core in the range of rank n, between the elements of rows n and n + 1, and at least one other coaxial cable which includes a winding of N turns on each of the n cores and in the same direction as the windings of said power line, and which is designed to supply voltage to at least the means for producing particles, the winding of the Interval of rank n being electrically isolated elements between which it is found. In this case and when the preferred embodiment of the invention, mentioned above (elements respectively provided with said other coaxial holes) is used, the accelerator object of the invention can be produced so that the core located in the interval of row n is annular, that the n cores and said n other holes associated with them are coaxial and that each other coaxial cable passes through these

n other holes.

  The present invention will be better understood from

  reading the following description, examples of

  embodiment given for information only and in no way limitative, with reference to the accompanying drawings in which: - Figure 1 is a schematic view of a first particular embodiment of the accelerator object of the invention, - Figures 2A and 2B schematically illustrate the coaxial target windings used in this first particular embodiment, - Figure 3 schematically illustrates electronic circuits capable of generating impulse supply voltages for the accelerator shown in Figure 1, - Figure 4 is a graph showing the temporal evolution of these impulse supply voltages, S - FIG. 5 is a graph which illustrates the hysteresis cycle of the ferromagnetic material of which the nuclei formed by the accelerator represented in FIG. 1 are made, and - FIG. 6 is a schematic view of a second particular embodiment of

  the accelerator object of the invention.

  In Figure 1, there is shown schematically a first embodiment

  particular of the accelerator object of the invention.

  In this first particular embodiment, the accelerator comprises a set of n + 1 electrically conductive elements in the form of plates, called

  "equipotential distributors" R1, R2, ..., Rn, Rn + 1.

  The distributors R1 to Rn are superimposed and drilled respectively with n coaxial holes T1, T2, ..., Tn, of the same diameter. The distributor R1 is electrically and sealingly connected to a vacuum enclosure 2 in the form of a cover, electrically conductive and grounded, which surrounds the hole T1 and which is drilled opposite this hole T1 to allow the exit of the particles. accelerated as we will see later. The enclosure 2 is tightly connected to a tube 4 o is created The vacuum and in which the accelerated particles continue their path in

  direction of. place of their use.

  The n + 1 equipotential distributors are electrically insulated from each other by n identical, electrically insulating and coaxial rings A1, A2, An. These rings have an internal diameter which is greater than the diameter of the holes T1, ..., Tn and each desditSanneaux connects two distributors in a sealed manner and surrounds the two holes with which these two distributors are respectively provided, all of the n insulating rings having the appearance of a tube which is called "insulator tube" and whose axis is that of holes T1 to Tn. The insulating rings can be made of plastic, glass or ceramic and the n + 1 equipotential distributors can be made of a metal plate. The seal between the different insulating rings and the distributors can be obtained by means of non-O-rings.

represented or by collage.

  Pumping means 6 are provided to create a suitable vacuum in the vacuum enclosure 2 and in the insulating tube, that is to say in the zone which extends from the distributor R1 to the distributor Rn + 1 and which

  is limited by the different insulating rings.

  The accelerator shown in Figure 1 also includes an accelerator electrode 8 which is disposed in the enclosure 2 opposite the opening with which it is provided. This accelerating electrode 8 is supplied with high pulse voltage by means of an electrically conductive tubular support which extends in the insulating tube along the axis Xl common to the holes T1 to Tn, up to the distributor Rn + 1 to which it is connected electrically and tightly. This distributor Rn + 1 is drilled along the axis X1 common to the holes T1 to Tn so that the tubular support 10 is tightly connected to the distributor Rn + 1 on the periphery of the hole 12 thus obtained. This hole 12 allows the passage of one or more coaxial cables 14 in the tubular support up to the accelerating electrode 8. This or these coaxial cables 14 can be used for

9 2632804

  different power supplies required for

  operation of this accelerating electrode.

  Assuming for example that the accelerator shown in FIG. 1 is intended to accelerate electrons, the accelerating electrode 8 is hollow and comprises, opposite the hole with which the enclosure 2 is provided, an element 16 which is capable of emit electrons when heated. To this end, a filament 18 is placed inside the electrode 8 opposite and near this element 16. The filament 18 is connected, at one end, to the core of the coaxial cable 14 and by its 'tre'extrême à La braid de ce cable 14. As will be seen below, ce- cable 14, one end of which is thus connected to the filament 18, has different windings and, at its other end, a continuous electrical voltage, supplied by a suitable source -20, is applied between the core and the braid of this coaxial cable 14, this continuous tension being suitable for heating the filament 18. When this filament is heated, the element 16 is also heated and emits this made electrons. These electrons are then accelerated in the acceleration space between the accelerating electrode 8 and the hole

  which is provided with the enclosure 2 and pass through this hole.

  For the acceleration of electrons, the high electrical impulse voltage which is applied to the accelerating electrode is negative, the enclosure 2

being grounded.

  The equipotential distributors which are in the form of a plate, protrude widely on one side of the tube

  insulator mentioned above, on the left side of it

  Ci in FIG. 1. The accelerator represented in this FIG. I further comprises, on the said side, a set of n-1 annular ferromagnetic cores. and laminated F1, F2, ..., Fn-1. These nuclei are coaxial and their axis

2632804

  common X2 is parallel to the axis X1 common to the rings A1, ..., An so that the set of superimposed cores is parallel to the insulator tube, each core being between two equipotential distributors, namely F1 between R1 and R2 , F2 between R2

and R3, ..., Fn-1 between Rn-1 and Rn.

  Each ferromagnetic core has for example a toroidal shape of rectangular section and can be made of ferrite, of laminated sheet of Fe-Si or better, of an amorphous material of the type of that which is marketed under the name "VITROVAC" or that which

  is marketed under the name "METGLAS".

  The equipotential distributors Rl, R2, ..., Rn are also pierced respectively with n holes tl, t2, ..., tn which are coaxial, have a diameter less than the inside diameter of the ferromagnetic cores F1 to Fn and have an axis common confused

with the common axis of these nuclei.

  In the case where coaxial cable 14 is used, another ferromagnetic core Fn identical to the previous ones is also included between the distributors Rn and Rn + 1, the axis of the core Fn being the axis common to the other cores. A hole tn + l is then provided on the distributor Rn + l, the axis of the hole tn + 1 being the axis common to the holes tl to tn. This hole tn + l allows the passage of the coaxial cable 14, after it has undergone different windings on the cores as we will see later and before this coaxial cable 14 does

  enters the tubular support 10.

  The accelerator shown in FIG. 1 also includes n coaxial cables C1, C2, ..., Cn which all have the same length, as well as n electronic circuits CE1, CE2, ..., CEn which are respectively associated with the n cables coaxial Cl, ..., Cn and which will be described later. Each of the coaxial cables C1, ..., - Cn is connected by one end - or input end - to the electronic circuit which corresponds to it - then comprises a certain number of windings - except for The cable C1 which has no winding - after which its other end - or outlet end - is connected to certain distributors

  equipotenties, as will now be explained.

  At the outlet end of the cable Cl, the core of this cable Cl is electrically connected to the distributor R2 and its braid is electrically connected to the

distributor R1.

  From its entry end, the cable C2 passes through The hole tl, makes N turns on the core F1 and, at its exit end, its core is electrically connected to the distributor R3 and its braid to the

distributor R2.

  From its entry end, the cable G3 crosses tl, makes N turns on the core Fl1 crosses t2 then makes N turns on Lenoyau F2 and, at its --20 exit end, its core is electrically connected to the

  distributor R4 and its braid to distributor R3.

  More generally, from its input end, the cable Ci, i being an integer greater than 1 and less than or equal to n, makes these N turns on each of the cores 1, 2, ..., i-1 successively and, at its outlet end, its core is electrically connected to the distributor Rî + 1 and its

braid to distributor Ri.

  Thus, the cable Cn does the N turns on each of the cores F1, F2, .., Fn-1 successively and, at its output end, its core is connected to the distributor Rn + 1 and its braid to the distributor Rn ( see Figure 2A in which the cable 14 is not shown). The direction of the windings and the same on all

1 2 2632804

  the kernels concerned and for all the targets.

  The various electrical connections of the coaxial cables Cl, ..., Cn with the appropriate distributors R1 to Rn can be made, for the sake of simplicity, on the edges of the axis holes X2 corresponding to these distributors, these holes serving for the passage of cables of a stage (zone delimited by two

  distributors) to the other of the accelerator.

  Each of the electronic circuits CE1, ..., CEn is designed to supply at the output, in synchronism with the other electronic circuits, a pulse voltage v of sign suitable for

  particles to accelerate as we will see later.

  This voltage v is applied to the core of the input end of each cable Cl, ..., Cn, the braid of which is, at this end, grounded. Each coaxial cable 14, Cl,..., Cn is a high voltage coaxial cable, capable of supporting said voltage v, which is equal to 20 kV, for example, without an under-circuit. Furthermore, to avoid any short circuit between the distributors due to the coaxial cable windings which are placed between these distributors, each distributor R2, R3, ..., Rn is provided on its two faces, on the side of the insulator tube o are located the cores, of an electrically insulating coating 21 for example made of an electrically insulating plastic material capable of withstanding the voltage v. It is the same for the distributors R1 and Rn + 1 except that for the latter the coating 21 is simply placed on the respective internal faces of these distributors R1 and Rn + 1. The coaxial cables 14, Ci, ..., Cn can also be provided with an electrically insulating sheath. The coaxial cable 14 provided with the voltage source 20 at its input end, accomplishes the following path from this end: it crosses the hole tl, makes N turns on the core Fl, crosses the hole t2, makes N turns on the core F2, and so on to the core Fn on which it makes N turns then exits through the hole tn + 1 and passes into the tubular support 10 (see also FIG. 2B on which the cables Cl, ... , Cn are not shown). The direction of the windings of the cable 14 is the same as the direction of the windings of the cables Cl to Cn. The structure of the windings of the cables Cl to Cn, which we have just described, means that, on each stage, or zone delimited by two equipotential distributors, the imputation voltage v is increased by. The quantity v if v is positive, or on the contrary is reduced by The quantity v if v is negative (case of the acceleration of electrons for example). Consequently, since there are n-1 stages - respectively associated with the nuclei F1 to Fn-1, the high impulse voltage V which supplies the accelerating electrode 8 and which is in fact established in the space of acceleration is worth

v + (n-1) v = n.v.

  For example, for an accelerator of 400 keV, in Lequet the high impulse voltage V is equal to absolute value, 400 kV, and which comprises a total of 20 stages (n = 20), The impulse voltage v having to be applied to each of the cables Cl, ..., Cn

  is in absolute value equal to 20 kV.

  The number of turns N is determined in such a way that it is at least equal to: -1 vtS (DB) formula in which t represents the duration of a pulse, S represents the cross section of each toric nucleus and DB represents the variation

  admissible induction in this nucleus.

14 2Z632804

  If you use METGLAS 2605 Co cores, for which the quantity DB is equal to 3.4T and which have a cross-section of 55 cm, the number of turns N necessary for pulses of duration or width tI equal to 2.5 microseconds is equal to 3. I The windings of the coaxial target 14 allow it to transport, without breakdown, the voltage supplied to it by the source

, -up to the filament 18.

  In FIG. 3, the electronic circuits CE1, ..., CEn for supplying the coaxial targets C1, ..., Cn have been shown diagrammatically. These n electronic circuits are identical and the diagram of one of them them, namely CE1, is represented on

Figure 3.

  Each of these electronic circuits makes it possible to arrive at the impulse voltage v (equal to V / n) starting from a direct voltage which is successively established and interrupted at the desired rate thanks to a plurality of transistors which form a switch and which are controlled by pulses

  appropriate frequency.

  More specifically, each circuit such as CE1 comprises conventional means 22 which are capable of supplying a DC voltage of 300 volts per

  rectification of the voltage supplied by the sector.

  This direct voltage is available in one, referenced bl, of the two terminals of the means 22, the other

  terminal b2 of these means 22 being grounded.

  The circuit CE1 also includes a plurality of power MOS transistors 24 which are connected in parallel. The sources of these transistors are grounded. A generator 26 sends control pulses, of duration t, to the gates of the transistors 24, these gates being 'connected to each other at 1s5 2632804 others at a point referenced b3. This generator 26 sends the same control pulses, in synchronism, to all the circuits. CE1, ..., CE More precisely to all the grids of the transistors of these circuits. Returning to the circuit CE1, the direct voltage from the means 22 is applied to a terminal b4 of the primary circuit of a transformer 28 and the other terminal b5 of the primary circuit of this transformer 28 is connected to the drains of the transistors 24. These transistors 24 thus make it possible to generate a pulse of duration t and of amplitude 300 V. I At the input end of the coaxial target Cl, the braid of this cable is grounded while its core is connected to a terminal b6 of the secondary circuit of the transformer 28 and thus receives a pulse voltage intended to constitute the pulse voltage v. The other terminal b7 of the secondary circuit. of transformer 28 is connected to ground via an electrolytic capacitor 30 whose terminal - is connected to terminal b7 and which serves to

  demagnetize the different nuclei F1, F2, ..., Fn.

  To obtain a pulse voltage v of amplitude 20 kV, the transformer 28 must have

  a transformation ratio equal to '20000/300 or 66.

  Of course, this transformer 28 is mounted in such a way that a pulse voltage v (and therefore a high pulse voltage V) of suitable sign is obtained for the accelerated particles. In the case of electrons, the voltages v and V are negative as we have already

indicated above.

  The current supplied by the transistors 24 can be calculated from the average current I of the particle beam that one wishes to accelerate. For example,

16 2632804

  if we want I to be of the order of 100 mA and if the -

  pulse frequency is 4 kHz, the accelerated peak current should be of the order of 10A and the transistors 24 should provide a total of about 660A. However, we find in the trade transistors capable of providing

  A. We will therefore use 15 transistors in parallel.

  For a number n of circuits equal to 20, the accelerator control therefore requires 300 power MOS transistors. Each electronic circuit such as CE1 also includes an electrolytic capacitor 32 and a fast diode 34 connected in series between the terminals of the primary circuit of the transformer 28: The terminal - of the capacitor 32 is connected to the terminal b4 and its terminal + to the anode diode 34, the cathode of which is connected to terminal b5. A Zener diode 36 is mounted between the terminals of the capacitor 32: its anode is connected to the

  terminal b8 and its cathode at terminal b4.

  Another electrolytic capacitor 38 is connected to ground by its terminal - and to terminal b4 by its terminal +. The capacitor 32 has the function of absorbing the demagnetization current of the transformer 28 and the capacitor 38 has the function of filtering the

mains voltage rectified.

  The fast diode 34 and the Zener diode 36 are provided for adjusting a voltage v which ensures the demagnetization of the transformer 28. Of course, the sign of this voltage v is suitably chosen as a function of the charge of the particles to be accelerated. It 0 is positive in the case where these particles are electrons. If we take a voltage v of 30 volts, the demagnetization l takes about 25 microseconds. This voltage v is applied to terminal b7. An electrical resistor 40 is mounted between ground and point b3 and has the function of polarizing the gates of the transistors. In Figure 4, we have shown the variations of -v as a function of time t assuming negative v. The demagnetization of the nuclei F1 to Fn-1 is in principle ensured by the negative part of the curve of FIG. 4. The application of the voltage v contributes o

  also to this demagnetization.

  -The curve of figure'5 represents the hysteresis cycle of the material constituting the ferromagnetic nuclei F1, ..., Fn, this curve showing the variations of the magnetic induction B as a function of the magnetic field H. The point of the cycle corresponding to demagnetization is the point al for which L H is zero and B is -Br (remanent induction). An impulse corresponds to the course of the right branch of the cycle, from point al to. point a2 which corresponds to Bsat (saturation induction). The DB quantity mentioned above is such that:

DB = Br + Bsat.

  In the first particular embodiment, synchronous electronic circuits and cables C1 to Cn of the same length were used so that the voltage pulses v arrive simultaneously at the stages which correspond to them respectively and can be added to give the voltage V Alternatively, an accelerator can be designed in which the cables Cl, ..., Cn have different lengths and are respectively associated with electronic circuits. which supply pulses of voltage v having, relative to each other, time delays calculated as a function of the different lengths of the cables, so that the pulses of voltage v always arrive simultaneously at the stages which correspond to them respectively. In Figure 6, there is shown schematically a second particular embodiment of the accelerator object of the invention, which

18 2632804

  reduces the number of windings on the

  ferromagnetic nuclei F1 to Fn-1.

  This second embodiment differs from the first by the fact that the n coaxial cables C1, ..., Cn are replaced by a single circuit formed by n sections of high voltage coaxial targets of the same length cl, c2, ..., cn , able to support La

  impulse voltage v without breakdown.

  The sections c2, c3, ..., cn each make N turns in the same direction, respectively on the nuclei Fl, F2, ..., Fn-1. For all i, i being greater than or equal to 2 and less than or equal to n, the section ci has an inlet end situated on the side of the distributor Ri-1 and an outlet end situated on the side of the distributor Ri. For any pair of adjacent sections ci and cit1, taken from sections c2 to cn, the core of the outlet end of ci is electrically connected to the core of the inlet end of ci + l as well as to the distributor Ri + 1 as seen in Figure 6 and the braid of the outlet end of ci is electrically connected to the braid of the end

  input of ci + 1 as well as to the distributor Ri ..

  In addition, at the input end of the section cl, the voltage v generated by an electronic circuit of the kind shown in FIG. 3 is applied to the core of the cl while the braid of the latter is put to ground and, at the outlet end of cl, the core of the latter is connected to the core of the inlet end of c2 as well as to the distributor R2 while the braid of cl is connected to the braid of

  the input end of c2 as well as the distributor R1.

  Finally, at the outlet end of cn, the latter's core is electrically connected to the distributor Rn + 1

and its braid to the distributor Rn.

  The coaxial cable 14 is connected in the way

19 - 2632804

  shown in Description of Figure 1 and performs

  still N windings in the same direction as the windings of the sections c2 to cn, on each of the

nuclei F1 to Fn.

  The distributors R1 to Rn + l are also provided with electrically insulating coverings 21 as in the case of A

  explained in the description of Figure 11 to avoid

  short circuits between these distributors. In addition, the coaxial cables 14 and cl to cn can be provided

  an electrically insulating sheath.

2632804

Claims (8)

  1. Electrostatic accelerator of charged particles, operating in pulsed mode, comprising: - means (16, 18) for producing said particles, - at least two electrodes (2, 8) which are provided for the acceleration of these particles, one (8) of the electrodes, called the accelerating electrode, being intended to be brought, relative to the other electrode (2), to a high pulse voltage V capable of creating between the electrodes an electric field which accelerates the particles, said other electrode being pierced to allow the passage of accelerated particles, and - means for bringing the accelerating electrode to the high pulse voltage, this accelerator being characterized in that the means for bringing the accelerating electrode to the high pulse voltage include : - a set of n + 1 electrically conductive elements superimposed (R1, ..., Rn + 1) which are electrically isolated from each other, this set thus having at one end a element of rank 1 and at its other end an element of rank n + 1, n being an integer at least equal to 2, the accelerating electrode (8) being electrically connected to the element of rank n + 1 and said other electrode (2) being electrically connected to the element of rank 1, - at least n-1 ferromagnetic cores (F1, Fn-1), the n-1 cores being respectively placed in the n-1 intervals defined by the elements of rows I to n (R1, ..., Rn), and - at least one power line (C1, ..., Cn cl, ..., cn), Said power line comprising n-1 windings of N-turns : of coaxial target in the same direction; respectively around said n-1 ferromagnetic cores (F1, ..., Fn-1) - and being designed to bring the Element (Rn + l) of rank n + l to the high impulse voltage V by means of a impulse voltage equal starting point for Wine, by increasing this starting voltage by V / n at each of said n-1 intervals from the first of these, N being a number greater than 1.   2. Accelerator according to claim 1, characterized in that it comprises n electric lines respectively constituted by n coaxial cables (Cl, - Cn), in that, for any integer p greater than or equal to 2 and less than or equal to n, the cable of rank p, makes said N turns on each core of rank less than or equal to p-1, in that, for any whole number k greater than or equal to 1 and less than or equal to n, the braid and l of the output end of the coaxial cable of rank k are respectively electrically connected to the element of rank k and to the element of rank k + 1, the voltage V / n being applied between the core and the braid from the input end of each of the n coaxial cables, in that each winding is electrically isolated from the elements between which it is placed and in that the length of each cable and the moment of application of the voltage Vi / n at each cable are such that the Vin voltages arrive simultaneously   at the cable outlet ends.   3. Accelerator according to claim 1, characterized in that the electric line is unique and comprises n sections.cc1, ..., cn) of coaxial cable of the same length, in that the sections of rows 2 to n respectively include the n-1 windings, in that, for any whole number p greater than or equal t 2 and 22 2632804   less than or equal to n, the braid of the entry end of the section of row p is electrically connected to the braid of the exit end of the section of row p-1 as well as of the element of row p- 1 while the core of the entry end of the section of rank p is electrically connected to the core of the outlet end of the section of rank p-1 as well as of the element of rank p, in that the voltage V / n is applied between the core and the braid of the entry end of the section (cl) of rank 1, in that the braid and the core of the outlet end of the section of rank n are respectively electrically connected to the element of rank n and to the element of rank n + l and in that each winding is electrically isolated from the elements between which it is placed.   4. Accelerator according to any one of   claims 1 to 3, characterized in that the   electrodes (2, 8) are located opposite the element of rank 1 so that the accelerating electrode (8) is included between the latter and said other electrode (2), in that the elements (R1, ..., Rn) of rows 1 to n respectively have n coaxial holes (T1, ..., Tn), in that said other electrode (2) is tightly connected around its periphery to the element (R1) of rank 1, in that each element is tightly connected to the element of immediately superior rank by a sealed and electrically insulating ring (A1, ..., An) which surrounds the holes of these two elements and in that the accelerating electrode (8) is electrically connected to the element (Rn + l) of rank n + l by an electrical conductor (10) which passes through the n holes. 5. Accelerator according to any one of   claims 1 to 4, characterized in that the   elements (R1, ..., Rn) of rank 1 to n respectively comprise n other coaxial holes, (tl, ..., tn) provided for the passage of said line, in that the n-1 ferromagnetic cores (F1 , ..., Fn-1) are annular and coaxial and in that the axis- (X2) common to the cores and the axis common to said other holes are combined.   6. Accelerator according to claims 4 and   5, characterized in that the axis (X2) common to the cores (F1, .- .., Fn-1) and the axis (Xl) common to said holes- (T1, Tn) are parallel.   7. Accelerator according to any one of   Claims 1 to 6, characterized in that it comprises   10. additionally a ferromagnetic core (Fn) in the range of rank n, between the elements of ranks n and n + 1, and at least one other coaxial cable (14) which comprises a winding of Ntours on each of the n cores and in the same direction as the windings of said electric line, and which is designed to supply voltage to at least the means (16, 18) for producing particles, the winding of the range of row n being electrically isolated from the elements between which it is found.   8. Accelerator according to claims 5 and   7, characterized in that the core located in the range of rank n is annular, in that the n cores (F1, ..., Fn) and said n other holes (tl, tn) are coaxial and in that each other cable   coaxial (14) passes through these n other holes.