US2829249A - Apparatus for accelerating charged particles - Google Patents

Description

April l, 1958 H. R. KRA-rz 2,829,249

APPARATUS Fon AccELERATING CHARGED PARTICLES Filed Aug. 21. 1952 :s sheets-sheet 1 l Inventor:

Howard R. Kvatz, 2 b5 His .tctowvxey` April 1, 1958 H. R. KRATz 2,829,249

APPARATUS FOR ACCELERATING CHARGED PARTIcLEs Filed Aug. 21, 1952 f i s sheets-smet 2 "Env l 0075/? WM/@wss Flg. E? I l x x fk f 0 (l TER WIND/NGS wenas/M; r Y y www wmp/mas ITV GTTCCDP: Z Howard R. Kratz,

by. A His Attorneg.

Apil 1, 1958 H. R. KRA-rz 2,829,249

APPARATUS Fox ACCEL'ERATING HARGEn PAR'ncLEs Filed Aug. 21, 1952 3 Sheets-Sheet 3 rig. 44.

8574590 SBII 008/7' Pf6/0N P ra mamme o la 4r ans/fa Par/l Inventor* t Howard R. Kratz 'United States Patent() PPRATUS FOR ACCELERATING CHARGED PARTICLES Howard R. Kratz, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 21, 1952, Serial No. 305,613

9 Claims. (Cl. Z50-27) The present invention relates to apparatus for imparting high energy to charged particles, particularly electrons. .This invention relates particularly to and is an improvement over apparatus of the type disclosed in Patent 2,622,194, granted December 16, 1952, upony an application of James L. Lawson, Howard R. Kratz and George L. Ragan, Serial No. 196,482, filed November 18, 1950, and assigned to the assignee of the present application.

Itis now well known that energy of the order of several million electron volts or higher may be imparted to charged particles such as electrons by accelerating the particles in a generally circular path or orbit with magnetic induction effects. For example, apparatus for producing this result is disclosed inV U. S. Patent 2,394,071, granted February 5, 1946, to Willem F. Westendorp and assigned to the assignee of the present invention. Such apparatus yis commonly referred to in the art as a betatron, and itcomprises field generating means for providing a time-varying magnetic flux which links the orbital path to accelerate the particles and a time-varying magnetic guide field which traverses the locus of the orbital path for constraining they particles thereto.

It is also known that further energy may be imparted to charged particles such as electrons by subjecting them to the repetitive action of a localized cyclically-varyingv electric field after they have been accelerated to a desired energy level by the above-mentioned betatron apparatus. Suitable apparatus for achieving this purpose is disclosed in U. S. Patent 2,485,409, granted October 18, 1949, to Herbert C. Pollock and Willem F. Westendorp and also assigned to the assignee of this invention. This latter apparatus can be referred to as synchrotron apparatus utilizing betatron start. It generally comprises means such as a high frequency resonator coupled to the charged particle orbital path for applying a localized cyclicallyvarying electric field to accelerate the particles after they have been pre-accelerated by betatron action, and means for producing a time-varying magnetic guide field traversing the locus of the orbital path for constraining the particles thereto during the application of the electric field.

Both of the forms of accelerator apparatus disclosed in the above-mentioned patents employ Yanl iron core for the production of the proper magnetic fields andy fiuxes. cause such an iron core must be laminated'to minimize the generation of eddy currents and has great weight, fabrication and handling present major problems. vMoreover, it is very difficult to eliminate azimuthal field asymmetries, and the limitations upon magnetic inductionimposed by saturation of the iron necessitate large amounts of stored energy in the accelerator apparatus. The aforementioned Lawson et al. Patent 2,622,194 showsthat thedisadvantages represented by theiron core may be obviated by the expedient of producing the desired magnetic fields and fluxes with non-ferromagnetic field generating means. f Y

In the aforementioned Patent 2,622,194 there Vvis disclosed non-ferromagnetic .charged particle accelerating 'apparatus which comprises non-ferromagnetic field generating means enclosed by a metal tank adapted for internal evacuation. Within the metal tank is disposed a nonferromagnetic liner which has the same general shape as the tank and also encloses the field generating means.

The field generating means includes two sets of windings,

one of which provides the requisite time-Varying magnetic liux and guide field for initially applying betatron acceleration to charged particles suitably introduced into the tank, and the other of which provides the time-varying magnetic guide field which is required during the subsequent period of synchrotron acceleration. This construction allows the placement of the synchrotron guide field windings in a region closely adjacent the stable orbitaly satisfactory, it has been found that the set of betatron As shown and described in the aforesaid patent, the set lof windings expends morey power than is desirable.

betatron windings comprises four individual coils or windings suitably coupled with the charged particle orbital p'ath to produce the betatron field and flux. For obtaining a stable region surrounding the orbital pathY of suiiciently great cross-sectional area to permit fully successful acceleration of charged particles, it has been found necessary to locate the individual betatron windings farther from the orbital path than was anticipated. This has two undesirable effects: (l) the coupling to the orbital path s less, thus reducing the efficiency of the windings; and (2) the windings, being nearer the non-ferromagnetic liner,

cause more power to be wastefully dissipated in the liner by currents generated therein. j

It is a principal object of the present invention to provide a means for reducing the power Yconsumption of nonferromagnetic betatron field and ux generating windings.

' f According to one aspect of the present invention, there is provided improved non-ferromagnetic charged particle yaccelerating apparatus which comprises four betatron windings for a given extent of the stable region of acceleration surrounding the orbital path, there is provided an auxiliary winding located in the plane of the orbital path. The auxiliary winding is energized such that it carries a current fiowing in a predetermined direction with respect to the current in the remaining four betatron field and flux generating windings, whereby the net field of the four Abetatron windings is modified ina manner which' permits their location more closely adjacent `the' orbitalv path for a given desired extent of the stable orbital region. Following initial acceleration of the charged particles with the five-winding geometry of the invention, synchrotron acceleration of the charged particles to higher energy'.Y

levels can be accomplished, if desired, by the provision'of synchrotron guide field windings and a cyclically-varyingelectric field coupled to the electric path.

Other objects and advantages of this invention willbe apparent from the following description taken in ,connection with'the accompanying drawings in which Fig.` 1 is a sectionalized elevation of non-ferromagneticsynchrotron apparatus suitablyembodying the invention and taken along line 1-1 ofk Fig. 2; Fig. 2 isa sectionalized view Patented Apr. 1, 1958 graphical representations useful in explaining the invention; Fig. is a schematic diagram showing exemplary circuit connections for energizing the apparatus of Figs. 1 and 2;.and Fig. 6 is another graphical representation useful` in explaining the invention.`

Referring now to Figs. l and 2, there is shown nonferromagnetic charged particle. accelerating apparatus according to the invention comprising an air-tight tank 1 which may` befevacuated, through a `suitable connection 2 attached `to the baseplate `3 of tank 1. Base plate 3 and a cover plate 4 may be retained in air-tight relation with respect to a cylinder. 5 by means of a plurality of peripherally spaced screws inserted through circular gaskets 7, which may consist of a suitable synthetic rubber material. Basle` plate, cover plate 4, and cylinder 5, which dene chamber 5', must beA of `sufficient thickness to withstand internal evacuation without` serious deformation and, therefore, should consist of a high tensile strength materiaLsuchas steel or iron. p

. Supported from base plate 3 by means of circular dielectricmspacer` members 8 and 9 is a liner l0, the function of which will be more fullyv described hereinafter. Liner 10 preferably consists of a highly, conductive non-ferromagnetic material `such as copper and comprises a base plate 11,'a, cover plate 12 and a hollow cylinder 13. Base plate 11 and cover plate12rare attached to cylinder 13 by means of alplurality o f peripherally spaced screws 14, and

an`orit`1ce-15 is provided in base plate 11 to permit inter-- nal evacuation of` liner 10 through connection 2. For the sake.- of` symmetry,an orifice 15' is situated in cover- Plate 12..

`In order'to` provide for the injection of charged particles suchas electronstfor accelerationwithin liner 10, there is, showna` source assembly 16 which may comprise an electron gun 17 `having altilamentary cathode (not shown) suitable for injecting, in responseto intermittent energiza-A tion, aburst of electrons` into` the charged particle orbital.

path indicated at;` point x. Structural details for gun 17, whicbrmaybe `advantageously employed in connection with thepresent invention, are disclosed and claimed in U. S. Patent 2,499,192,` granted February 28, 1950, to James M. Lafferty and assigned to the assignee of the present invention.w Guni17 maybe supported within a hollow tubel of ahw-conductivity, non-ferromagnetic t materialrsuch` as .stainless steel andenergized through conductors. (not shown) insulatingly introduced through tubel. y A slot lisprovidedin the lower end of tube 18to permit theegressof electrons from gun 17. Tube 18x is ared outwardly at its upper end to receive in' hermetierclationship an insulator 19 and is also hermetically sealed adjacent its upper end to a base member 20.

An apertured. plate 214 Ais helduY bymeans.. of screws 22` gun 17 is maintained by meansof a stud 29 and-nuts 3G,v

thelattenof which may-tbe" screwed `up or down to adjust bellows 25. ASeveralstuds 29,' along with nuts 30, may

beflocated `around the periphery of `base member to insure desired positioning of gun'17.'

Aslhasbeen mentioned heretofore, the present inventin; contemplates the Y betatron acceleration` Aof injected charged particles with non-ferromagnetic field` generatingr means capable of supplying both a time-varying magnetic flux ywhich linksthe orbital path of the charged particles* to impart acceleration theretoy andga time-varying mag neticlguide teldwhich traverses the-orbital pathfor` the` purpose `of constraining the charged particles thereto. Ac-

cordingly, beta'tron windingsl, 32,133Jand-34 are-shown' potliti'oned` adiacentithe orbital'ipath `indicated at point x;-

of voltage (not shown) such that the current through all the windings ows in the same direction for a purpose to be more fully described hereinafter. Conductors 36 are hermetically sealed within tank 1 by means of insulators 37, apertured plates 38, screws 39v and packing material 40. To prevent a conductive connection to liner 10, conductors 36 are inserted therein through apertures 41. Windings 31, 32', 33 and 34 are respectively supported from base plate 11 of liner 10 by means of dielectric spacers 42, coil supports 43, 44, 45 and 45, cylindricallyshaped spacer members 47 and-48 and dielectric shimming members 49, 50," 51 and 52.

To assure the retention of `proper positioning of field generating windingsl, 32, 33 and 34, as well as of other components of the accelerating apparatus, during operational periods when tremendous forces are exerted thereupon due to the magnetic fields and fluxes which are generated, various support members are provided. These members include dielectric spokes 53fwhich bear attheir outer` ends againstanged hollow cylindrical members 55. Outward radial thrust may be imparted to spokes 53 by means of spreaders 56. Spreaders 56 comprise lower beveled cylindricalldielectric blocks 57 having studs 58 extending therefrom. Upper dielectric cylindrical beveled blocks 59 are apertured to permit the extension therethrough of studs 58 and block members 57 and 59 may be drawn together to exert outward radial thrust against cylindrical members 55. by means of dielectric nuts 60 which threadably engage stud 58. Notched circular dielectric spacer 61. is provided, as shown, to assure proper separation of members 47 and 48. To exert radial thrust between cylinder 13 of liner 10 and flanged cylindrical members 62, cylindrical spacer members 63 and 64 are employed in'connection with spreader members 65, which are similar to the above described spreader members 56 l and compriseupperand lower blocks 66 and 67, studs 68, and nuts 69. Y i

The Ndielectric `materials-utilized to form the various above-mentionedY supports -must be able to withstand the tremendous-forcestwhich areexertedltherreupon when the accelerating apparatusis `in operation; Furthermore, the

" by winding glass cloth,which has been impregnated with a suitable organic resin,4 around a steel mandrel having a desired shape. Afterthe desired form has been obtained in this manner, the support may be cured and stripped from the mandrel in amanner well known to those skilled in the. art. Subsequently, the supportmay be machined tothedesirecl dimensions. A suitable organic resin may consist of.-diallyl phthalate anddiethylene glycol maleate alongwith a` polyvinyl. formal resin obtained by the partial .hydrolysisolf polyvinyl acetate and the reaction ofjhefpartially hydrolized` product with formaldehyde.

It willnow appear. that, if the betatron field and flux producing windings.31--34areenergized from a source of time-varying. voltagein. a manner to be more fully dscribedher'einaftemacceleration in-an orbital Pahf charged. particleslinjected fromv gun 17. may be obtained, providingtthb ,well known betatron flux and iield consider ations `are satised.` Thebetatron relationships which` they time atrwhichthe magnetic induction' B' is aero, ro

. (1 where'lnpisthe total changein tlux linking the orbit from agsaaatn is the radius of the o'rbit, and Bo is the magnetic vinduction at the orbit; and

where n is an exponent having a value between O and 1, B is the magnetic induction at a position under consideration and r is the radius of such a position. Equation 1 represents the ux-field condition which must be complied with to secure successful acceleration, and Equation 2 represents a stability condition which must be fulfilled before the charged particles will execute stable oscillations along and in the vicinity of the orbital path. In

order to satisfy Equation 1, which need be met only along the stable orbit x, with two windings outside and two winding inside stable orbit x as shown, it is necessary to have the current liowing in all the windings in the same direction, whereupon the flux linking the orbital path is then in the same direction from both inner and outer windings while the field traversing the orbital path from the inner windings is opposite that from the outer windings. With the proper ratio of the number of turns in the outer windings to the number of turns in the inner winding, Equation 1 can be fulfilled. Equation 2 requires a nearly'uniform field which falls off in proportion to l/rn in the region along and adjacent orbital path x. In order to fulfill Equation 2, it is necessary to match the shape of the magnetic induction curves of inner windings 31, 34 and outer windings 32, 33 such that the net magnetic induction falls off at the proper rate with the radius in the orbital region. In Fig. 3, curves of magnetic induction B in the orbital plane versus radiusV r are shown for both inner windings 31 and 34 and outer windings 32 and 33. It will be observed from Fig. 3 that the desired falling off of magnetic induction with radius to give a value of n lying between and 1 can be obtained at or near the field maxima of both inner and outer windings. This is more clearly shown in Figs. 3a which can be considered as an enlarged View of the righthand portion of Fig. 3.

It has been found in practice, however, that the proper positioning of windings 31-34, to secure a stable region surrounding the orbital path in accordance with Equation 2 of sufiicient extent to permit fully successful acceleration of the charged particles, requires the location of, these windings at relatively great distances from the orbital path. This reduces the coupling to the orbital path and hence reduces the efficiency of windings 31-34.`

And since it is desirable to keep the dimensions of liner l@ as small as possible to reduce the volume which must be evacuated, the positioning of windings farther from the orbital path places them nearer liner 10, thereby iucreasing wasteful power dissipation from eddy or image currents generated in the liner as la result of the timevaryin.'J currents flowing in the windings. y

When the net magnetic induction of vthe windings StL-34 is plotted as a function of radius for various planes above and below the plane of the orbit, it is observed that the exponentvn, which is proportional to the absolute magnitude of the slope of the magnetic induction versus radius curves, decreases in moving vertically (or in the Z direction parallel to the axis of the windings) from the orbital plane. It is this decrease in n that limits the vertical or Z direction extent of the stable orbital region. As the windings 31-34 are placed nearer the orbit, n decreases more rapidly and the stable region surrounding the orbit becomes smaller. According to the invention, this decrease in n in the vertical or Z direction is made less rapid by positioning an auxiliary winding 69 in the plane of the orbital path as illustrated;

in Figs. 1 Yand 2. Winding 69 has a radius smaller than that of the orbit andis connected, as will be more fully described` hereinafter, in series with windings 31-34 so that itlcarries a current flowing in the s ame direction as the currentrin windings 31-34. VAlthough Winding 69' is shown as comprising only one turn, it can have addi`i tional turns depending upon the number of ampere-turns that are necessary to produce the desired compensation for the decrease in the n of the windings 31--34.

The magnetic induction yof winding 69 alone, plottedA netic induction of windings 31-34 in the orbital plane;

hence the n value of net magnetic induction of the entire combination of windings 31--34 and 69 decreases more t slowly with Z than does the magnetic induction of windings 31--34 alone. This is readily understood from the fact that the magnetic induction of winding 69 decreases the n value of the net magnetic induction of windings 31-34 more in the orbital plane than above or below it. Since the n'value of the entire combination of windings 31--34 and 69 decreases more slowly with Z, it thus becornes possible to locate windings 31-34 nearer the orbit without decreasing the extent of the stable orbital region in the vertical or Z direction.

s, The utilization of auxiliary winding 69 also affects# the n value of windings 31-34 in the radial direction.

The magnetic induction of winding 69 decreases the` value of n in the orbital plane, but thisV effect is more pronounced at radii smaller than the orbit since the n value of the magnetic induction of winding 69 (which subtracts from the n of windingsv31-34) increases asy the winding itself is approached. As the winding 69 -is approached from the orbit, the n value for the entirecombination of windings 31-34, 69 actually decreases Y' to zero and becomes negative. The radius atpwhich n becomes zero is determined by the radius of winding 69' and the magnitude of the magnetic induction from wind` ing 69' as compared withV the magnetic induction from windings B11- 34. By a proper choice of the radius and number of turns of winding 69', the extent of the stable region can be extended to smaller radii without much affecting the radius outside the orbit at which the field becomes unstable. 69' can increase the total extent of the stable region in the radial direction as well as in the vertical or Z` Of course, the magnitude of the magnetic direction. induction which can be supplied from winding 69 yis ultimately limited by its effect upon the magnetic induction outside the orbit.

Although it is preferred to position winding 69 in the plane of the orbital path and with a radius smaller than the path, it can also be employed in the plane of the orbit with a radius larger than the path. In such event,v

the energization of winding 69' can be by a series connection with windings 31-34, but the current in winding 69' must flow in a direction opposite to that in wind-v l ings 251-34.

in the inner section must be in the same direction as the current in windings 31--34 and the current flow inthe outer section must be in the opposite direction.

While it is known that the above-stated Equations 1 and 2 both must be fulfilled to obtain betatron acceleration of the charged particles, it has proved impractical to` I calculate accurately the field configurations resulting fromv windings 31-34 and 69' because of the difficulty of con-4 sidering the effect of liner 10. Liner 10 is employed,.

in conjunction with tank 1, as a shield for the field generating windings and `for external apparatus. YLiner 10,. however, reducesvthe field at the orbit and the flux linking` the orbit'and alsov changes the phases'of the field 4and' 'flux In this' way the addition of winding with respectto the current in windings 31--34, 69'.` Consequently, the most effective procedure for locating` whichsatises Equatioirl along orbital path x and` also` produces a satisfactory `field `variation in `bothlsadial and vertical directions over the desired stable' region in lthe vicinity of the orbital path as `required by Equation 2. After windings 31m-34,` 69' have been installed within liner 10, vertical `adjustment to correct for field discrep ancies may be obtained :by Imeans of shirns49--52. With the above-described winding .configuration a stable region of relatively large extent adjacent the orbital path `can be obtained, the shape `of suchfa `region `being indicated by the solid `line representation of Fig, 4.

After'thechargedparticles have been accelerated to the desired energy level byrneans of betatron flux and field producing windings 31-34 and 69", further energy can be imparted to the particles by means of a cyclicallyvarying `electric field produced by a high frequency circuit including a resonator 7 0i Resonator 70 isof the opencircuited coaxial line type in which a portion of an electrostatic shield 71, whose general functions will be more fullydescribed hereinafter, serves as the `outer conductor and a lplurality of vertical conductors 72 serve as the inner conductor. Both electrostaticshield 71 and inner conductors 72are` constructed of a plurality of separate wires of a non-ferromagnetic conductive material such as copper depending from cover `plate .12 of liner 10 as shown, the individual wires being` secured together by means of a desired `insulating organic resin, such as the abovementioned diallyl phthalate and diethylene glycol maleate.

This form of construction serves to minimize the generation of disturbing eddy Lcurrentsgwhen the accelerating apparatus is'in operation. Withinconductors 72 a similar pluralitycf conductors 73 are provided, which, along with conductors `72, may subtend an arc of about 60 adjacent orbital path x. Conductors 72tand 73 areV bent outward at their upper ends and soldered at 74 to a circular lplate 75 of a nou-ferromagnetic conductive material such Ias copper which is secured, along with shield 71, to `cover plate 12 by means of right angle' circular clamping members 76 and bolts 77 constructed from a non-ferromagnetic conductive material such as copper. Arcuate dielectric member 78 is positioned within conductors 73 `to provide rigidity for theyconductor assembly comprising conductors 72 and 73. Each of the;wires of`shield71` and each of the conductors 72 Aand 73 may be provided, respectively, with circumferential slots 79, 80 and 81 `to interrupt continuous current'paths for unwanted eddy currents.

It will `now be observed that, if resonator 70 is excited with an energized concentric line `i12 hermetically introduced through cover plate 4 by means of a vacuum-tight bushing 83 and inductively coupled into resonator 70 at 84, a cyclically-varying electric field will be produced between outer conductor 71 and inner` conductor 72, such a field fringing out atthe ends of resonator 70 tocouple with the orbital path x. lf this electric field is of the proper frequency, energy may be imparted to charged particles during each revolution within orbital path x. Assuming that the `charged particles are electrons and have been accelerated to approximately the velocity of light within orbital path x by betatron flux and field generating `windings 31-34, their approximate :frequency j" will be given `by the followingrelation:

where `c lrepresents thevelocity of light. Consequently, thejfrequency of excitation of resonatorf70 maybe arranged at a constant value such that energy is imparted to the charged particles upon each revolution.

According to the present invention, conductors 72 areprovided with extensions extending downwardly and about the charged particle orbital path x while conductors 73 terminate vertical extension, above the path as indicated. This Yprovides an R. F. field-free region 85 throughout .the vcircumferential extension of conductors 72 and 73, `such field-free region serving to shield the .charged `particles ,from the` R. E, fields within resonator n, while they are within region S5'. Therefore, if the frequency of excitation of resonator 7i) is equal to or a multiple of `the frequency given a Equation 3 for electrons, energy may be imparted` to the electrons a function ofthe timeatwhich they enter and leave resonator 7G.

Of course, charged particles moving along orbital path x are affected by any electric held which couples thereto. In order to prevent deleterious results, therefore, it is necessary to shield the orbital path from unwanted electric fields, e. g. those resulting from the clcctric potentials upon `the various windings within the accelerator apparatus and those derived from charges collecting upon partsof the apparatus `(especially insulators). Elec trostatic shield 71, described hereinbefore, acts to perform this function. Shield 71 may be constructed of hollow wires and water-cooledit excessive overheating is encountered. Slots 79, as well as slots 39 and 81, may not be necessary, providing the respective conductors lie within close limits in planes passing through the axis of the accelerator apparatus.

In order to provide a time-varying magnetic guide field to constrain the charged particles to orbital path x as energy is being imparted thereto by resonator '70 in accordance with the .principles hercinbcfore discussed, windings 86,87, S8 and G9 are disposed adjacent orbital path xdwithin circumferential slots in cylindrical spacer members 47 and 48 as shown. windings i3d-89 may comprise a plurality of tubes through which a suitable coolant such aswater may be circulated and to which energy may be supplied through hermetically sealed conductors (not shown) introduced through tank 1 in a manner similar' to conductors 36. The magnetic field provided by windings 36-39 must meet the requirements of Equation l2 in that the magnetic guide field within the region surrounding orbit x must have the desired inverse slope with increasing radius; but the flux generated by windings 86-89 need not meet the requirements of Equation 1 since, Vduring the period of energization of windings 86-89, energy is imparted to the charged particles by means of resonator 70 and not by means of a time-varying magnetic flux linking the orbit, as is the case during betatron acceleration. To produce a field complying with Equation 2 alone, a more efcient field producing arrangement may be employed, viz. windings 86-89 may be connected in series to a suitable source of time-varying voltage (not shown) such that the current in the two inner windings 86 and 89 flows in the opposite direction to the current flowing in the two outer windings 87 and 83, the direction vof current flow in the outer windings being the same as the current flow in betatron windings 31-34 and 69. This results in a greater guide field intensity for a given winding current because the fields are 4additive within the stable orbit region. The value of the exponent n in Equation 2 in this instance depends upon the relative vertical spacings of the outer windings 87 and S8 compared to the relative vertical spacings of the inner windings 86 and 89, and the desired value may be obtained with the outer windings slightly farther apart vertically than the inner windings. The crossesectional area of the orbital stable region will have dependent dimensons, i. e. the vertical extent may be increased by moving the windings farther apart vertically (without altering relative vertical spacings) but the horizontal extent will be decreased simultaneously and however, they cannot be in too close proximity because, v

matterfthe cross-sectional -A even though the amplitude of the charged particle osci1 lations has been damped during the betatron start period,

the charged particles still undergo some oscillation about orbital path x. Moreover, even though the charged parl ticles are electrons and have been accelerated to nearly i the velocity of` light during the betatron start period,

there is a slight increase in radius vof orbital path x as ar result of relatively small velocity increase during chrotron acceleration to high energylevels.

Referring now to the exemplary circuitry of Figs. 5

syn-

.and 6,4 the following sequenceof events takes place afterv switch 100 of Fig. 5 is closed. As will be observed, betatron flux and lield generating windings 31-34 and 69', which may be series resonated with capacitors 101, are connected to be energized in series by a time-varying alone. If it is found that the region surrounding the"` orbital path can not be evacuated suiiiciently, electrostatic shield 71 in conjunction with the cover plate 4 of Y tank 1 can be formed into a separate hermetically sealed without actually departing from the invention. I therefore aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters 4 Patent of the United States is:

source of voltage, such as alternating current source 102 pulse in its secondary circuit as the current through windings 31-34, 69' and the flux generated thereby goes through zero. In a few microseconds thereafter when the magnetic induction at the orbital path x has reached particles can be accelerated along an orbital path; means for injecting said charged particles for acceleration within Asaid chamber; a setof windings for accelerating said particles along said orbital path including an outer pair of windings having aY diameter greater than said orbital path, an inner pair of windings having a diameter less than said orbital path and a winding positioned essentially in the plane of .said orbital path adjacent and substantially non-coplanar to said inner and outer windings, said windings in said inner Aand outer pairs being connected together for current ilow therethrough in the same direction, each winding in each of said inner and outer pairs of windings being disposed on the opposite side of the a value which causes charged particles of several kilovolts energy to be constrained thereto, such as the point a of Fig. 6 wherein the net magnetic induction B inthe orbital plane is plotted versus time, gun 17 is energized by means of pulse generator 104, the initiation of which is deter,- mined by delay device 105. The charged particles which are thus introducedinto orbital path x are accelerated by the betatron ilux and field generating windings 31--34 and 69until they have reached a desired energy level, at` which time delay device 106 causes highV frequency. gen.

erator 107 to energize resonator 70. Within close proximity thereto, delay device 108 causes pulse generator 109 to energize synchrotron guide field windings 556-89. This latter sequence may be arranged to occur at point b as indicated on Fig. 6. After the charged particles have been accelerated further or desired additional energy has been imparted thereto by synchrotron guide field windings 86-39 and resonator 70, delay device 111 may be rendered effective to deenergize high frequency generator 107 at point c whereby the charged particles spiral inwardly from orbital path x from impingement upon a suitable target (not shown). Alternatively, delay device 111 can be rendered operative after the magnetic induction peak d has been traversed, e. g. the point e on Fig. 6, whereby the charged particles spiral outwardly and may be directed to a suitable target 112 (Fig. 2) for the production of desired effects. If the charged particles are electrons, high energy X-rays may be generated in this manner and extracted from tank 1 through a circumferential groove 113 (Fig. l) within cylindrical member 48, a slot 113 in shield 71 (Fig. 2), and a port 114 (Fig. 2).

It will be understood by those well skilled inthe art that various forms of delay devices, pulse generators, and high frequency generators may be employed to secure the above mentioned purposes. It will'also be understood that windings 31--34, 69 and capacitors 101 can be energized in parallel by means of source 102 and transformer 103, although the above described series connection is to be preferred because harmonics in supply voltage are ltered and short-circuits in windings 31-34, 69 are current-limited. From the foregoing description, it is apparent that windings 31-34 and V69 can be advantageously employed without the associated synchrotron windings and circuitry for the purpose Vof accelerating charged particles to high energy levels by betatron etects planey of said orbital path in relation to the remaining winding of each respective pair and all ofV said windings enclosing a space which is substantially free of ferromagnetic material; and means for simultaneously energizing all of said windings including a source of time-varying voltage connected thereto.

2. Apparatus for accelerating Vcharged particles comprising means providing a chamber within which charged particles can be accelerated along an orbital path; means for injecting said charged particles for acceleration within said chamber; a set of windings for accelerating said particles along said'orbital path including 'an outer pair of windings having a diameter greater than said orbital path, an inner pair of windings having a diameter less than said orbital path and a winding positioned essentially in the plane of said orbital path adjacent said inner and outer windings, said windings in said inner and outer pairs being connected together for current flow therethrough in the same direction, each winding in each of said inner and outer pairs of windings being disposed on the opposite side of the plane of said orbital path in relation to the remaining winding of each respective pair and all of said windings enclosing a space which is substantially free of ferromagnetic material; and electric conducting means connected to and interconnecting all of said windings for simultaneously supplying a time-varying voltage thereto to produce coincidentally both a time-varying magnetic flux which links said orbital path to accelerate said charged particles and a time-varying magnetic guide lield which traverses said orbital path to constrain said particles to follow said orbital path within a relatively large radially and axially extending stable region surrounding said oroital path.

3. Apparatus as in claim 2 in lwhich said winding positioned essentially in the plane of said orbital path has a diameter less than the diameter of said orbital path and is wound and connected relative to the remainder of said y windings so that when energized it carries a current flow- ,owing in a direction opposite to that flowing Ain the` remainder of said windings.

5. Apparatus as in claim 2 in which said Windinglpositioned essentially inthe plane of said orbital Vpath includes two sections, one of said sections having a diameter greater than that of said orbital path and the other of said sections having a diameter `less than that of said orbital path, said one section being wound and connected relative to the remainder of said windings so that when energized it carries a current owing in a direction opposite to that oiving in the remainder of said windings and said other section being wound and connected relative to the remainder of said windings so that when energized it carries a current tiowing in the same direction as that flowing in the remainder of said windings.

6. In non-ferromagnetic accelerating apparatus wherein charged particles are accelerated along an orbital path by means of a set of non-ferromagnetic cored windings connected together for currenttlow in the same direction to supply a time-varying magnetic ux that links the orbital path to accelerate the charged particles and'a time-varying magnetic guide eld that traverses the orbital path to constrain the particles thereto, the improvement which comprises means for increasing the stable region within which charged particles `can be accelerated along the orbital path including a non-ferromagnetic cored winding positioned essentiallyv in the plane of the orbital path and Iconnected for simultaneous energization with said set of windings to supply magnetic ux and tield supplementary to the magnetic ux and eld supplied by the set of windings.

7. In non-ferromagnetic accelerating apparatus wherein charged particles are accelerated along an orbital path by means ofa set of non-ferromagnetic cored windings connected together for current flow in the same direction to supply a timevarying magnetic flux that links the orbital path to accelerate the charged particles and a time-varying magnetic guide field that traverses the orbital path to constrain the particles thereto, the improvement which comprises means for increasing the stable region within which charged particles can be accelerated along the orbital path including a non-ferromagnetic cored,

winding positioned essentially in the plane of the orbital path and connected in series with the set of windings to` supply magnetic flux and iield supplementary to the 5magnetic, ux and held supplied by they set of windings.

8L ln a non-ferromagnetic synchrotron having a set of betatron windings connected together for current ow in the same direction for initially accelerating charged particlesalong an orbital path and electrieeld producing means for continuing the charged particle acceleration,

the improvement which comprises means for increasing the stable region within which `charged particles can be accelerated along the orbital path including a non-ferromagnetic cored winding positioned essentially in the plane of the orbital path and connected for simultaneous encrgization with said betatron windings to supply magpath and connected for simultaneous energization with` said betatron windings to supply magnetic ux and iields supplementary to the magnetic flux and fields supplied by said betatron windings.

References Cited in the file of `this patent UNITED STATES PATENTS 2,465,786 Blewett Mar. 29, 1949 2,473,477 Smith June l4, 1949 2,533,859 Wideroe Dec. 12, 1950 2,622,194 Lawson et al. Dec. 16, 1952 2,736,799 Christotilos Feb. 28, 1956`

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