US3278745A

US3278745A - Radio-frequency particle separator

Info

Publication number: US3278745A
Application number: US332318A
Authority: US
Inventors: Gregory A Loew
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-12-20
Filing date: 1963-12-20
Publication date: 1966-10-11
Anticipated expiration: 1983-10-11

Description

Oct. 11, 1966 V G. A. LOEW RADIO-FREQUENCY PARTICLE SEPARATOR Filed Dec. 20, 1963 POWER SOURCE 3O UTILZATION DEVICE |O PARTICLE SEPARATOR V COUPLER DEVICE TUBE ACCELERATOR TARGET INVENTOR GREGORY A. L05 w ATTORNEY United States Patent Atomic Energy Commission Filed Dec. 20, 1963, Ser. No. 332,318 2 Claims. (Cl. 250--41.9)

The present invention relates to a radio-frequency particle separator capable of physically separating high energy charged particles such as electrons, protons, pi mesons, etc., moving at slightly different velocities in a charged particle beam. The invention is generally utilized in conjunction with a bubble chamber or counter and is disposed to accept a particle beam generated by bombarding a target with, for example, a beam accelerated by a linear accelerator. The resulting desired portion of the particle beam emerging from the invention is thus available for further physics research.

Various devices are presently available for providing the desired separation of particles in a high energy beam having energies greater than, for example, 1 billion electron volts (BEV). Such devices include for example, electrostatic separators, standing wave cavity separators, and traveling wave separators using various slow wave structures.

The present invention provides an extremely simple and straightforward structure which exhibits stronger defecting properties for a given amount of radio-frequency in put power than do the above-mentioned devices. When dealing with particle beam energies of the order of, for example, 20 BEV and higher, such efliciency in the use of input power to the separator is extremely advantageous.

The invention utilizes generally a cylindrical, periodically disk-loaded Waveguide with nonconcentric apertures formed in the disks through which the charged particles to be separated are made to drift. Unlike magnetic particle separators the invention causes a deflection of- Wanted and unwanted particles in accordance with the difference in their velocities and their entrance phase and not due to the difference of momenta. The electromagnetic wave which is propagated through the guide is of the TM type. The transverse deflecting property of the device is caused not by the choice of the TM mode of propagation as. in conventional radio-frequemcy separators, but by off-centering the disk apertures,

and causing the propagation of radio-frequency energy in the separator in the same basic mode as used in a related linear electron accelerator tube. The transverse deflecting property of the device is caused by the asymmetry obtained by off-centering the disk aperture. Thus, the particle separator of the present invention by means of its construction and related mode of electromagnetic wave propogation exerts a transversely deflecting force on charged particles synchronized with the propagated wave. Hence, if microwave power is made to propagate along such structure, particles which are synchronized with the wave at the correct phase will undergo a cumulative transverse deflection whereas particles traveling at a dif ferent velocity will, on the average, undergo no deflection. With a bunched beam and a short structure, if particles of different velocities are caused to drift with respect to each other by half a wavelength prior to their injection into the separator, they will be deflected in diverging directions and thereby be physically separated into two distinct beams.

Accordingly it is an object of the present invention to provide a simple device capable of separating particles in a very high energy particle beam at a particular frequency, wherein the particles are moving at slightly different velocities.

It is another object of the present invention to provide a particle se'parartor which utilizes a TM type mode propagated therein to realize the desired deflection of particles passing therethrough.

It is still another object of the present invention to provide a travelling wave particle separating device of relatively high shunt impedance and a corresponding, inherent, high deflecting efficiency.

Yet another object of the present invention is to provide a radio-frequency particle separator wherein the transverse deflecting property of the device is provided by cit-centering the disk apertures and causing the propagation of radio-frequency energy therein in the TM mode which is the same mode as that in the accelerator tube.

Another object of the present invention is to provide a radio-frequency particle separator which reduces the possibility of mode rotation in the structure, which rotation generally exists in separators using the TM mode, wherein the reduction is due to the inherent asymmetry of the structure of the device.

Other objects and advantages will be apparent in the following description and claims considered together with the accompanying drawing, in which:

FIGURE 1a is a perspective partially broken-out schematic view of the radio-frequency patricle separator of the present invention.

FIGURE 1b is a graph of the electric field generated within the separator of FIGURE 1a as a function of the radial distance along a line defined by the central axes of a disk and its aperture.

FIGURE 2 is a block diagram of a portion of an accelerator system in which known elements are shown combined with the particle separator of the present invention.

Referring more particularly to the drawing, there is shown a radio-frequency particle separator 10 in accordance with the present invention, comprising substantially a cylindrical disk-loaded waveguide. More particularly, an elongated cylindrical waveguide 12 having an inside radius b and a centrally extending geometrical axis lying along the z-coordinate, has disposed concentrically within and along the length thereof a series of equally spaced disks 14. Each of disks 14 has an aperture 16 formed therein in nonconcentric relation to the cylindrical waveguide 12. That is, apertures 16 in disks 14 are disposed in off-axis relation to the centrally extending geometrical axis of the waveguide 12. Apertures 16, however, are arranged in alignment along a common longitudinal axis thereof which axis is parallel to and spaced from the axis of waveguide 12. Thus, a particle beam 18 containing high energy charged particles moving at different velocities, and which is generated by bombarding a target with a suitable high energy particle beam, is injected into the separator 10 along the apertures 16 therein. Such beam 18 is separated into the desired number or configurations of distinct beams, e.g., 20, 22 and 24. If the apertures 16 are disposed off-axis in a horizontal direction with respect to the axis of the Waveguide 12, as shown in FIG. 1a, then the direction of deflection of the emerging beams 20, 22 and 24 is along the same horizontal plane.

In operation, an electromagnetic wave of the TM type is supplied to the cylindrical waveguide 12 from an exterior radio-frequency power source 30 (FIGURE 2) by means of a suitable coupler device 31 which is coaxially secured at the input end of the separator. The coupler is, in essence, a cavity of suitable dimensions and operates to convert the incoming radio-frequency power from the TE mode of the rectangular waveguide to the TM mode of the circular separator. Since coupling of power to waveguides by means of couplers is known standard practice, no further discussion thereof is believed necessary. The transverse deflecting property of the separator 10 is supplied not by the TM mode propagated through the guide as in most traveling wave separators, but by the asymmetry of the propagating field which in turn, is obtained by off-centering the disk apertures 16 in accordance with the invention. The longitudinal electric field E along the z or axial direction, which would normally be constant over the respective disk apertures if same were centered along the axis of the waveguides 12, is seen in FIGURE 1b to undergo a variation as a function of the distance across the disks. The phase shift per cavity defined between successive disks 14, and hence, the phase velocity of the wave propagated therein at the given frequency, may be determined by the choice of the axially extending distance d between disks 14 and the inside radius b of the cylindrical waveguide 12. A typical applicable phase shift is 1r/2 or 21r/3 per cavity. The cross sectional dimensions, a and b, of the device are determined by the choice of the frequency of the microwave power source to be used. Thus, in accordance with the invention, the apertured disks are spaced apart a distance substantially equal to XO/n, where A is the free space wavelength, and n is the desired number of disks per wavelength. Further, the inside diameter of the cylindrical waveguide 12, i.e., the outside diameter of the disks 14 is approximately equal to AO/ 1.305, the diameters of the apertures 16 are approximately equal to kO/S, and are formed in the disks 14 with their respective centers disposed a distance approximately equal to AO/S from the axis of the cylindrical waveguide 12 and along a common axis. The length and number of cavities of the device depends on the energy of the particles to be separated, the desired angle of separation and the magnitude of the available microwave power. A typical power source for introducing the desired driving radiofrequency power to the separator by way of the coupler would be a high power klystron.

While the invention has been disclosed herein with respect to a single preferred embodiment, it will be apparent to those skilled in the art that numerous modifications and variations are possible within the spirit and scope of the invention, and thus it is not intended to limit the invention except by the terms of the following claims.

What is claimed is:

1. A particle separator for separating high-energy particles having different velocities, comprising:

(a) a radio-frequency power source for generating electromagnetic waves of a preselected frequency;

(b) a cylindrical waveguide, the inner diameter of said waveguide being substantially equal to Ml/ 1.305, Where A0 is the free space wavelength of said electromagnetic waves;

(c) means for coupling said radio-frequency power source to said cylindrical waveguide in the TM mode; and

(d) a plurality of disks concentrically mounted within said waveguide, said disks being spaced apart a distance substantially equal to AO/n, where n is the desired number of disks per wavelength of said electromagnetic wave, said disks having apertures of a diameter substantially equal to AO/S, which apertures are aligned along an axis which is disposed substantially AO/S from the axis of said waveguide.

2. A particle separator according to claim 1, further including means for generating a high-energy particle beam, 2. target in the path of the beam upon which the beam impinges to generate a high-energy secondary beam which includes charged particles of at least two different velocities, said target being arranged to direct said secondary beam through said coupling means to enter along the axis of said apertures, and wherein said coupling means is of a length causing the particles of different velocities in the secondary beam to spatially separate therealong by approximately half a wavelength of the electromagnetic waves generated by said source.

References Cited by the Examiner UNITED STATES PATENTS 2,818,507 12/1957 Britten 25041.9 2,911,532 11/1959 Tipotsch 250-4l.9 3,093,733 6/1963 Blewe'tt et al 250-419 RALPH G. NILSON, Primary Examiner.

W. F. LINDQUIST, Assistant Examiner.

Claims

1. A PARTICLE SEPARATOR FOR SEPARATING HIGH-ENERGY PARTICLES HAVING DIFFERENT VELOCITIES, COMPRISING: (A) A RADIO-FREQUENCY POWER SOURCE FOR GENERATING ELECTROMAGNETIC WAVES OF A PRESELECTED FREQUENCY; (B) A CYLINDRICAL WAVEGUIDE, THE INNER DIAMETER OF SAID WAVEGUIDE BEING SUBSTANTIALLY EQUAL TO $0/1.305, WHERE $0 IS THE FREE SPACE WAVELENGTH OF SAID ELECTROMAGNETIC WAVES; (C) MEANS FOR COUPLING SAID RADIO-FREQUENCY POWER SOURCE TO SAID CYLINDRICAL WAVEGUIDE IN THE TM01 MODE; AND (D) A PLURALITY OF DISKS CONCENTRICALLY MOUNTED WITHIN SAID WAVEGUIDE, SAID DISKS BEING SPACED APART A DISTANCE SUBSTANTIALLY EQUAL TO $0/N, WHERE N IS THE DESIRED NUMBER OF DISKS PER WAVELENGTH OF SAID ELEC-