US2683216A

US2683216A - Apparatus for accelerating charged particles by causing them to pass through periodically reversing potential fields

Info

Publication number: US2683216A
Application number: US766698A
Authority: US
Inventors: Wideroe Rolf
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1946-01-31
Filing date: 1947-08-06
Publication date: 1954-07-06
Anticipated expiration: 1971-07-06
Also published as: FR931083A; CH253582A; NL93309C; DE847318C; GB663816A; NL72891C; BE467090A

Description

July 6, 1954 R. WIDEROE APPARATUS FOR ACCELERATING CHARGED PARTICLES BY CAUSING THEM TO PASS THROUGH PERIODICALLY REVERSING POTENTIAL FIELDS F i-led Aug. 6, 1947 2 Sheets-Sheet l a, +5 W My MAG/V5770 F7620 62/?55 ENVELOPE JNVENTOR:

July 6, 1954 R. WIDEROE 2,683,216

APPARATUS FOR ACCELERATING CHARGED PARTICLES BY CAUSING THEM TO PASS THROUGH PERIODICALLY REVERSING POTENTIAL FIELDS Filed Aug. 6, 1947 FIG. 6

2 Sheets-Sheet 2 JNVENTOR:

Patented July 6, 1954 APPARATUS FORv AC CELERATING CHARGED 'PARTIGLES'BY CAUSING THEM TO PASS THROUGH PERIODICALLY REVERSING POTENTIAL FIELDS Rolf Wideroaposlo Norway, assignor to Aktiengesellschaft Brown, Bove'ri & Cic, Baden, Switzerland, afjoint-stock company Application August 6, 1947', SerialNo. 766,698 In Norway January 31, 1946 Section 1,'P.ublic Law 690, August 8, 1946 "Patent expires January 31, 1966' 7 Claims.

1 This invention-relates to apparatus for accelerating charged particles such" as electrons, ions,

and the like to highvelocities, and in particular In Fig. 1 which illustrates 'the already known principlesinvolved, the "field's are established electrostatica'lly' by a row of tubes -T, T1, T2, T3, T4 etc. Alternate -tubes in thisrow, i. e. T1, T3,..Ta andTz, T4 are-connected to-thesame terminal of analternatingcurrent, source and preferably one having. a'high frequencycharacteristic, the oddnumbered tubes Ti etc.; being. connected to' terminal P and the even numbered tubes. Tz' etc. connected to. "terminal" P... If an electron for ex.- ample is inside of'tube T1 which happens to be charged negative at the instant assumed, it will not only find a' free path ahead of 'it but will also be accelerated in the direction of the-nextadjacent positivelychargedgtube T2 and drawn into thelatter... After entering -thei tube T2, the polarity of the field intubev Tachanges to negative and the polarity of the following tube T3 becomes positive during the time interval when the electron traverses the tube T2 and consequently 'a iurther accelerationof the electron is obtained. This step-by-step method of increasing the" velocity of the particles continues throughout the wholerowof tubes. As 'thefrequency at which the fields of the tube are reversed is maintained constant, and the passage 01"- the particles-fromone tube to another must be properly timed with the-change in polarity of the tube 'fields; it Wl11"b -evidentthat because of the continually increasing speed. of the particles,

successive tubes in the-row must be of increas ing length.

If-veryhighterminal Velocities of the particles is desired and high frequencies-are used'fo'r reversing the accelerating field's, it will" be obvious that extremely long tubes will be required; The

long-tubes notonly present spaceproblems but 2 also obviously require a high charging current which of course necessitates correspondingly large high frequency generator apparatus. These drawbacks limit the practical range of operation of the apparatus to voltages of a few million volts which hereinafter isshortened to MV, and restricts its use to the more heavier oi the ions.

The object of the present invention-is'to provide an improved construction for charged particle accelerators of the type described which overcomes the disadvantages inherent in the prior known structures,;-the objective being attained by an apparatus for the acceleration of charged particlessuch as electrons, ions, etc., comprising an evacuated chamber, an" electrode system of spaced-tubes and 'a source of high frequency alternating current for energizing the electrodes of said system to establish potential fields of alternate polarity in thespacings between said tubes, 'said'particles passing through said potential fields and'being-accelerated in accordance with periodic reversals of said fields, andthe improvement wherein said electrodes constitute a part of a high frequency transmi sion line of the coaxial cable or Lecherwires type and have a spacing corresponding to a fourth part, or a multiple thereof, of the wave length of the standing voltage waves in said transmissionline, said electrodes being so arranged that as to each electrode the particles move therein between points that at the same time possess diiferent potentials.

Fig. 2 illustrates one embodiment of an accelerating device constructed inaccordance with the invention. The two high frequencyconductors establishing the transmission line-are formed by the'hollowcylinders 01, be, as, 194, and the rods bi, cabs, a4, and the charge particles travel through the potential fields at I, II, III and IV in succession. The frequency of'thestanding voltage waves is selected so that the electrons or-ions pass between the ends of successive hollow cylinders in exactly one-half cycle (or a multiple of the same) 'of the high frequency current. The potential between the conductors will therefore beequal for example as shown in Fig; 2 where the-full drawn line b1b1b2b2b3b3b4b4 indicates the potential of the one conductor and the dotted line maiazazasasarar indicates-thepotential of the other conductor) each time the charged particles pass through 'a potential field, and they are therefore accelerated each time with the entire high frequency'current.

Since the velocityof the'particles increases with increasing particle'voltage, the cylinders are made successively longer in accordance with the following mathematical relationship wi en]; Q

where c=speed of light v=speed of the particle m =inertia of the particles at rest e=charge of the particle U=kinetic energy of the particles measured in units of electron-voltage.

The wave lengths of the standing waves of the transmission line shall consequently be made longer.

In order for the aforesaid condition of resonance to be met and at the same time the electrons accelerated with the maximum alternating current, the wave length and the length of the standing waves (\51. should meet the requirement %i.t=%qi-=l where Z=distance between the electrodes, (p) and (q) are whole numbers that indicate the number of standing waves there are between the electrodes, and how often (q) the applied high frequency alternating current changes between the passage of the particles through the length of a tube.

Since he will always be smaller than (p) and (q) are selected so that'the best values for and Z are obtained. If, for example, electrons whose speed is about equal of the speed of light are to be accelerated, it will be best to choose (1)):3, and (q)=1, and then the following is obtained:

When the speed of the particles is smaller than half the speed of light, (p) =(q):l can be selected and the following is obtained:

This latter corresponds to the apparatus illustrated in Fig. 2.

The wave length for the standing waves can be adjusted as shown in Fig. 2a by the insertion of materials between the conductors, these materials having a dielectric constant, or permeability, greater than one. In order to obtain especially short wave lengths, it is preferable to insert material is with high dielectric constant in the neighborhood of the points of voltage maximums (voltage anti-nodes) while material 16 with high permeability should be placed preferably in the neighborhood of the points of zero voltage (voltage nodes). These materials should likewise have small alternating current loss characteristics. This latter should also be true for the transmission line itself. The wave lengths of the standing waves can also be adjusted with the aid of inductances 6i and capacitances 62 connected in series and parallel, respectively as shown in Fig. 2. To prevent absorption losses by the charged particles due to collision with the gas molecules, their acceleration should preferably take place in a high vacuum, which may be accomplished by enclosing the tubes in a container (as shown in Fig. 5 and 6) and evacuating the same.

The apparatus illustrated in Fig. 2 is especially suitable for the acceleration of relatively slow particles such as for example, ions below 10 MV, since with great speeds of the particles, long cylinders and very high frequencies are then necessary.

Fig. 3 illustrates an embodiment of the invention which is particularly suitable for the acceleration of very rapid particles with about the speed of light. This drawing also shows in the same way as Fig. 2 transmission line systems of Lecherwires consisting of alternating short hollow cylinders (03) and rods (b) in succession. In this case, the acceleration cylinders are made sufficiently short that the amplitude of the applied high frequency voltage changes but only a little in the time required for the electrons to move through the cylinders. If, for example, the cylinder is made cm. long and \-=6 m. is chosen, five acceleration tubes can be used in which the electrons are passed during the time that the amplitude of the high frequency voltage changes by no more than COS i30:86.7%

After the electrons have travelled through the first five tubes, they can then be further accelerated in another set of five tubes by another high frequency voltage wave displaced in phase from the wave associated with the first five tubes; and then still further accelerated in a third set of five tubes to which is applied a third voltage wave displaced 60 in phase from the wave associated with the second set of tubes. In this manner, the electrons can be accelerated in an uninterrupted series with the aid of a three-phase high frequency voltage supply source, the phases being designated on the drawing by UR, Us and UT.

In order to attain the highest possible voltage on the particles for a given overall length of the accelerating tube system, the accelerating tubes are to be made short. If the frequency of the applied alternating voltage is not to be too high, the relation is to be made high, i. e. materials with very high dielectric constant and permeability are to be used. The relation can be brought up to'above 15 (,M 225) and possible even up to about 35-40. It should be possible therefore to make the acceleration tubes about 10 cm. long, and to attain an acceleration of from 1 to 2 MV per meter.

If the speed of the particles is much lower than the speed of light, the apparatus illustrated in Fig. 3 can be used, but with the same values for the two wave lengths, a correspondingly smaller number of cylinders per phase must be used. If v=0.2.c., only one acceleration tube per phase is obtained. If the speed of the charged particles is lower still, the acceleration voltage diminishes. If v=0.133.c., then with one acceleration tube per phase, and a two-phase system, an acceleration voltage that amounts to cos. 145 of the maximum alternating voltage) is obtained.

accepts -Fromthis,; it. is seen-a that therange. of ense: of 13116 s! the particles can be given a--=circular motion by magnetic control field's and thereby made to pass through one or more acceleration tubes over and over again until" the desired high final velocity and voltage is attained 'for'the particles. Since the number of revolutions ofthe particles can be made very great, the initial acceleration voltage can be made much lower, for example about kv., than that required for the straight-line tube arrangements of Figs. 2 and 3'.

Fig. 4 illustrates, in somewhat diagrammatic form, an accelerating device for charged particles embodying the principles of the invention and wherein the particles are accelerated along a circular path. The device functions in accordance with the principles shown in Fig. 2 and is comprised of two symmetrically arranged transmission lines of concentric form. One line consists of an outer conductor '6 and aninner conductor 2 connected with the feed lines hand I respectively; the other line consists of an outer conductor 1 and an inner conductor 3 connected with the feed lines't and 3, respectively. Since the speed of the particles will be'greater than .5 0., as previously stated, 'Xsi can be selected equalto fi of the circumference 21iR. Two'voltage nodes are. then obtained, these being at It "and HM, where the electrodes can be shortcircuited. The ends i! and 52 have voltages displaced in phase by 180; and at these places are located the high frequency voltage convexities'.

The hollow cylinder ttbetween points It and lira past [his at earth'potential and the cylinder is cut apart at point. it'i'n order to preventedd-y currents from. being setup by the magneticfield l5. The two energy electrodes 'could'more over be disconnected at the nodes is and its,

an'd'thewhole intermediate se'ction'of the acceleration tube (that "can-be -isolated from-the energy: conducting electrodes) placedat ground potential.

In Fig. 4, twoenergy conducting electrodeunits are utilized andfthese are displaced 180 in. phase. In. lieu of the illustrated construction, the two electrode units .couldbe replaced with 'a single electrode unit, in which of the wave length of the standing wave forms a part of "tlie'accelen ati'on tube while the other portion of the accel eration'tube from the node of the wave rtothe potential field can be-grounded and isolated electrically from the high frequency alternating voltage.

Such an arrangement is illustrated in" Fig.. 5 where there is 'a vacuum vessel 23; 2 2 with a lateral projection 2t forthe electron gun 25, "as well as an acceleration system. The transmission-line consists of a single-electrode unit comprising two tubes is and 2%] which at the point Iii (where a'voltage node would form) are joined together, whiist'the other end "of the transmission line lSJCODIlECiJGd-lldfihd high-frequency gen erator 2 1. At theapoint ll :whereuthe parti'cl-es are accelerated. there is a high. potential .between the electrodes; there is a voltage antinode here. Along thepath E8 to. I! (over 2'!) the circular orbit 280i .'.the particles lies within an earthed' tube '22, and the particles which are brought through the. opening 2'1 into the acceler ation path cannot be influenced here by the acceleration voltage.

The acceleration. frequency has thus to-be made equal to the frequency of circulation of the particles, or equal to a multiple of this frequency, so that'the'. particles areaccelerated during each revolution by the potential field existing at the point of entrance I! to tube 20. The magnetic control field, which compels the particles-to follow a circular path, flows perpendicular to the plane of the drawing, Fig. 5, in the form of an annulus, the'inner and outer boundaries of which are defined by'the inner and outer diameters of the control field poles 29, 3Eshown in Fig. 6. To simplify illustration, the boundaries only of this control field are shown in Fig. 5 and are designated by thebroken lines 55'. The-circular tube 22, is is interrupted at the entrance I"! in order that the magnetic field should not cause any short-circuit currents.

In Fig. 4, the electrodes 2 and 3 within which the electrons are accelerated are shown connected through transformer 1'3 to a source M of high frequency current. Electrodes 2 and 3 together form a toroidal tube'that i'sopen between the electrodes II and t2, the tube being split lengthwise or formed'by parallel insulated conductors. In order tonulliiy centrifugal forces; the magnetic field i'i'apreviously' referred to, is set up in a plane perpendicular to the plane-of the drawing, and the Lorenz forces produced thereby serve to guide-the accelerating electrons along 'a'circular path within the electrode tube. The circling electrons may be stabilized *in both radial and axial directions by reducing the strength of the-magnetic held in a radially outward direction, but at a rate less than proportional to 3- If the voltage of the. electrons increases, their mass will likewise increase and the magnetic field'must the'reforeincrease in order toannul the increased centrifugal force. The field "i can therefore be producedfrom an alternating current source at a comparatively low frequency; for example cycles, in' order to control the path of the electrons. In" order that the electrons shall always follow approximately the same circular path of radius R, the relation between the control field I51 which'can bed-esignated B, and the electron voltage U should be-as follows:

. B= /U +2Ue- (WhenU e) 5 From Equation"5',.-it can b'e-seen 'thatt'he control: field :B; is accordingly to increase substantially proportional to the electron voltage. This equation further indicates that "the high frequency electron accelerating voltage applied to the electronsmust duringthe' course of the electron acceleration change in proportion to i. e. the'voltage is to diminish proportional to cos wtgwhen thecontrol field B increases proportional-to sin. wt. If. at thebeginningoi the elec-- tron acceleration, the accelerating" voltage is made somewhat too high; the above change can be oneittcdi.anda' constantihigh;frequency'voltage employed. If the magnetic field 13 increases more slowly than proportional to time, the electrons, due to the constant acceleration voltage, will receive too high a voltage and the radius of the electron path will increase. Since the speed increases less than does the circumference of the circle, the electrons will reach the electrodes too late. This phase lag will increase with each revolution of the electrons and cause the electron voltage to diminish. Such action will continue until the electron path is balanced exactly at the correct acceleration voltage, that corresponds to In this manner, a stable equilibrium state for the radius of the electron path is obtained.

When the electrons enter the accelerator with an initial voltage of 460 kv., for example, they have about 85% of the speed of light. The speed will increase subsequently to the speed of light (at MV, the difference is only about 9.23%). In order that the time of revolution shall be one high frequency period in all cases, the radii of the electron. paths, or else the frequency must i be changed during the acceleration period. If the former is selected, the control field B and the acceleration tube must be enlarged in the radial direction sufficiently to permit the necessary enlargement of the electron paths, (for example from 0.85 to 1). In view of the fact that it is advantageous from a constructional point of view to have as narrow a magnetic control field as possible, the initial voltage of the electrons should be as high as possible. fore of advantage constructionally to arrange the electron gun by which the electrons are produced outside of the acceleration tube as shown in Fig. 5. With such construction, the electrons can then be introduced with somewhat too great a voltage, so that they must pass along the inner wall oi the acceleration tube. A few short and thin retarding foils 40 applied there will slow down the entering electrons so that the latter receive exactly the voltage that corresponds to the innermost electron path. With increasing voltage, the radius of the path increases and the electrons are no longer disturbed by the retarding foils. Since the electrons can be introduced only during a short portion of a period of the high frequency field applied to the accelerating electrodes, the electrons are to be accelerated even in the electron gun with high frequency fields of the acceleration frequency, and are emitted only during a certain part of the period. The electrons can be introduced preferably at parts of the orbit corresponding to the nodes of the acceleration voltage, i. e. where the energ conductor is not present.

The rotating electron charge limited in the azimuth sense will induce a weak alternating current when it passes through a condenser 4| that is placed in the vacuum tube at places where the acceleration tubes are on earth potential. This alternating voltage can be amplified in an amplifier 42 and used for the control of the high frequency generator 2! in known manner as described for example in Radio Engineers Handbook by Terman published 1942, at pages 510 516. This is especially important when it is desired to change the frequency of the generator during the acceleration period, in order to meet the condition of resonance. In the latter case, the constants of the transmission line are to be likewise changed so that the generator will work It is there" ample one-half of it, the induced opposed Voltin resonance. This can be accomplished for example by using an inductive winding M connected between the leads from generator 2! and which is wound upon one leg of a rectangular iron core 45. Wound upon another leg of the core is a premagnetizing winding 46 energized from a source of direct current 47 through a potentiometer 48 by which the permeability of the core 45 can be adjusted.

For controlling potentiometer 48 automatically, use can be made of a discriminator which supplies a control voltage according to the variation in frequency of generator 2|, the control voltage in turn being applied to a servomotor 51 which then adjusts the setting of the potentiometer in one direction or the other dependent upon the sense of the frequency variation. A suitable discriminator circuit for this purpose can be found described on pages 654ff of the above mentioned handbook.

The tubes forming the circular path in Fig. 5 can also be slotted longitudinally at a plurality of places around the tubes as shown by slots 55, if desired.

An important constructional advantage is obtained if the magnetic control field B is closed through the surfaces inside the paths of the electrons and to apply the magnetizing winding around the iron core formed thereby as shown in Fig. 6. The result of this however will be that the varying core field will produce an electrical swirling field that tends to slow down the movement of the electrons. Since the core field will fill up only a part of the circular surface, for exage will be for example only one-fourth of the increase in voltage that corresponds to the increase in control field. The accelerator voltage in this case is to be made to agree, i. e. 25 greater than without the swirling field.

6 shows a section through the central axis 34-34 of an accelerating device of the kind illustrated in Fig. 5. The vacuum vessel is indi cated by the reference numerals 25, whilst 22 is the earthed tube extending from is through 21 to point 11, and the IS and 25 are the two electrodes of the transmission line. The flux of the magnetic field for guiding the particles is indicated by the dotted line 32, whilst 35 is the iron core. The magnet poles of the magnetic guide field are indicated by 29, 3t and 33 is the winding for exciting the magnetic field, the winding 33 being energized from a source of alternating current 33'.

When the electrons have attained the desired voltage, they can be withdrawn from the acceleration chamber by suddenly switching in an additional magnetic field (positive or negative that is superposed upon the control field. This can be effected through the instrumentaiity of a transformer 49, the secondary lsa of which is connected in the energizing circuit of winding 33 and the primary 4% of which is energized at the proper instant from a voltage source 5c.

In the same manner as in the case of a betatron constructional elements in the vacuum chamber that. might hinder their circulation.

Finally it should be mentioned, by way. ofexample, that with a radius .of the electron path of 1.5 meters, and a;maximum control fieldinduction of about 11,000 gauss; a maximum'kinetic energy of about 500. MV for theelectronsxcan be attained. The acceleration frequency should .be about .32 'megascycl'es (wave length ..7l.-.=.9.4 meters) whereby a frequency. .of about. 5.0: cycles for .the control .field .-'(accelera.tion. timeemax. l sec.) would :make possible an. acceleration voltage of about. kv... maximum.

.If it is desired to accelerate ions according to the principle-employed.inthe Fig.= 4 or licenstruction, the speed interval for the-particles will be so great that theresonance conditionxican not be met with a. constant accelerationfrequencyby changing the radii of thezpath. .Great disfiiculties will also be met with in changing theacceleration frequency and .the constants of the energy conductor within the required-range. In this .case, where in Equation 2 is small, a corresponding great value for q can be selectedand thusthe revolution frequency of the ions synchronized witha fraction of the acceleration frequency. If the speed of the ionsincreases, asmentioned'earlier, the radius of'the-path will increase and-the ions will automatically meet the resonance-condition and hold fast to -this below-synchron-ism .movement. If the magnetic control field diminishes according to the equation where 0 K 1, the Voltage of the ions U and B and .Bo :is'the magnetic :iriduction for the'radii B, respectively 130, path radius R, speed-.vand the revolution frequency 11 are determined by the following Equations 7 to "10, that hold true for For protons 6:930 MV and for deuterons 1860 MV. When the revolution frequency 1/ is to'be constantly equal to the following:

this gives the following equations .between the magnetic field Bo .(thatvarieslonly with time) and the path radiusR and the voltage Urespectively:

2 2 2 B z/K U 2 e o 13 With the aid of Equation 13, when B0;=,B0+ dt t scribed :later.

10 it is "easy to calculate the acceleration voltage necessaryfor synchronism to bB:fiS' fQ11 OWSZ When the-path radiusasaresultof increase in voltage, approaches the: greatest value that is possible constructively, theions are to .he brought outof .synchronism by means that will be de- With asychronous movement, the iens in the middle are-not accelerated and, as a result of the .increaseain the control field, the path radius therefore will-diminish. This continues until the ions, whose speed of circulation constantly increases, attain .a higher subsynchronousfrequency (q-z .q1) and synchronize withalnew fraction .of the acceleration voltage frequency, sosthat they-can be accelerated again.

In- .this way, the operation is continued until the ions have attained their maximum voltage. The acceleration frequency is .to vbe selected .so high that a relative 'diiference between the last two sub-synchronous frequencies is smaller than the dilference between. the greatest and smallest path radius. If deuterons with MV are to be accelerated, the maximum speed will be about 0.315 c. If the magnetic control field maximum is about ILOOO-gauss, the greatestpath radius will-beabout 1 .9 m. The smallestmultiple of q=5isselected -to agreewith an acceleration frequency "of .39.5 in. cycles or A-=7..6 .m. If 7\st is .made to equal 7\- (i. e. s,u=1), the spacing between. two voltage maxima (-p=13) will-be 11.4 m.- and.the maximum voltage will hereby lie almost. exactly. at the acceleration electrodes of the acceleration tube. The smallest path radius will be 20% smaller than the greatest, e..-abou.t 1.58m. When-the frequency of the control field is 50 cycles and -K= the maximum synchronousvoltage will be 14:11.8 kv.

:lfn order to tbring the ions out of synchonism, when the frequencyehange istooccur, various r methods can be used. The acceleration frequency coul-d be.-.changed somewhat, in the known w y, at definite times. It is also possible to change the acceleration voltage in the known way and to permit its value to descend below the previously calculated synchronous value (Equation 1.4). The modulating frequency introduced into generatorll by-the modulator 43 would int-his case need to diminish about according to an c function and'the synchronous and asynchronous time intervals (that will be approximately equal in size) wouldhave to be adjusted so that the :path radii would not exceed the permissible limits. Synchronism could also be =.-an-nuled by increasing the necessary synchronous'vol-tage u above the acceleration voltage present, that is assumed as being varied proportionalito i. e. proportional to cos wt. This can be accomplished for instance by; changing the control field through use of a modulator 5| connected in the circuit of energizing winding 33, the modulator being supplied from a relatively low frequency. alternating current source 52, and thus periodically increasing n "dt but without changing the acceleration voltage to agree. A simpler solution would be to change the form of the poles of the control field so that the control field diminishes less greatly (i. e. K becomes smaller) when the greatest path radius is reached. One suitable arrangement is illustrated in Fig. 6 where it will be noted that the outer edges of the upper and lower confronting pole faces 29, 39 terminate in annular protuberances 53. By reducing K from A, to /3 for instance, the synchronous voltage will rise to the double value, this being suflicient to eliminate synchronism. The same thing could likewise be attained by giving the acceleration electrodes a form such that the direction of the potential field changes and the longitudinal field component becomes smaller with the greatest path radius. In this way the acceleration voltage can be made smaller and can be brought below the synchronous value, so that synchronism is eliminated. In order that these geometrically conditioned solutions can be employed (which could likewise be used simultaneously) the acceleration voltage normally must not exceed the synchronous voltage more than 30% for instance and therefore must be varied proportional to dB dt as mentioned earlier.

The methods mentioned here could of course be used likewise for the acceleration of electrons when the original speed is so small, that the increase in speed exceeds the expanse of the control field in radial direction.

In conclusion, a gigator according to this invention for 100 MV deuterons with a greatest path radius of about 1.9 m. will weigh less than 130 tons and would therefore be much cheaper to construct than a corresponding cyclotron with a weight of over 5000 tons. It has likewise been shown that the gigator can accelerate ions likewise to considerably higher voltages than the apparatuses disclosed heretofore.

I claim:

1. In an apparatus for accelerating charged particles, a two-wire transmission line comprising a series of inner tubular electrodes arranged in spaced end-to-end relation and a conductor r individual. to each electrode, each said conductor extending longitudinally of and spaced outwardly from the electrode associated therewith, one end of each said conductor being connected with the adjacent end of the electrode preceding the electrode with which that conductor is associated and the other end of each said conductor being connected with the adjacent end of the electrode following the electrode with which that conductor is associated, and means for connecting said series of tubes and conductors to a source of high frequency alternating current to establish potential fields of alternate polarity in the spacings between the ends of adjacent tubes effective to accelerate said charged particles introduced into said series of electrodes at one end thereof, the spacing between electrodes in the electrode series corresponding to a fourth part, or a multiple 12 thereof of the wave length of the standing voltage waves produced in said transmission line.

2. Apparatus for accelerating charged particles as defined in claim 1 and which further includes capacitances arranged in parallel in said line between said conductors and electrodes and inductances arranged in series with said conductors.

3. Apparatus for accelerating charged particles as defined in claim 1 and which further includes dielectric material disposed at voltage anti-nodes in said line and high permeability material disposed at voltage nodes in said line.

4. Apparatus for accelerating charged particles as defined in claim 1 wherein said series of tubular electrodes are arranged rectilinearly.

5. Apparatus for accelerating charged particles as defined in claim 1 wherein the spacing between potential fields equals approximately half the length of the standing voltage waves in said transmission line, and wherein the wavelength of the high frequency alternating current is relatively much greater than that of the standing voltage waves whereby the amplitude of the voltage wave changes only slightly during the time required for the particles to pass between two or more potential fields.

6. Apparatus for accelerating charged particles as defined in claim 5 wherein said potential fields are established in groups of at least two and said groups of fields are energized respectively by separate phases of a symmetrical source of high frequency alternating current.

7. Apparatus for accelerating charged particles as defined in claim 1 and wherein a source of alternating current having the same frequency as that which establishes said potential fields is utilized for injecting said charged particles into said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,157,855 Koch May 9, 1939 2,222,902 Hahn Nov. 26, 1940 2,233,779 Fritz Mar. 4, 1941 2,242,888 Hollmann 11 May 20, 1941 2,245,670 Hollmann June 17, 1941 2,276,247 Hahn Mar. 10, 1942 2,280,824 Hansen Apr. 28, 1942 2,286,428 Mehler June 16, 1942 2,297,305 Kerst Sept. 29, 1942 2,398,162 Sloan Apr. 9, 1946 2,424,959 Alford Aug. 5, 1947 2,480,169 Westendorp Aug. 30, 1949 2,520,447 Wideroe Aug. 29, 1950 FOREIGN PATENTS Number Country Date 695,129 Germany Aug. 17, 1940 OTHER REFERENCES Production of Particle Energies beyond 200 M. E. V., Review of Scientific Instruments, vol. 17, No. 1, January 1946, pages 6-14.

Ein Neves Prinzip Zur Herstellung Hoher Spannungen, Wideroe, Band XXI, 1928, page 391, Archives fur Electrotechnik.