DE1117794B - Electron accelerator working with traveling field linear acceleration - Google Patents

Description

GERMAN

PATENT OFFICE

P 17634 Vmc / 21g

REGISTRATION DATE: DECEMBER 15, 1956

NOTIFICATION OF REGISTRATION AND ISSUE OF
EDITORIAL: NOVEMBER 23, 1961

The invention relates to an electron accelerator operating with traveling field linear acceleration, from an electron source in the form of a speed-modulating electron tube, which supplies a focused, density-modulated electron beam 5, and from a traveling-field linear accelerator as well as a coupling device bringing these two parts into cooperation.

The usual traveling-field electron accelerators that use a waveguide spaced apart Walls, which essentially delimit successive resonance cavities, will have normally excited by a high frequency vacuum tube such as a speed modulated one Electron tube that uses an electron beam source that introduces an electron beam into the waveguide Is provided.

The object of the invention is to create a device for exciting an acceleration waveguide and for pushing high voltage electrons in a single operation.

This is achieved according to the invention in that the coupling device uses both high-frequency energy as well as electrons of high energy are generated, with the high frequency energy as a voltage converter wave brings about further accelerations of the electrons in the traveling field linear accelerator.

The invention is illustrated by means of exemplary embodiments in the drawing. It shows:

1 shows a schematic representation of a preferred embodiment of the electron accelerating device according to the invention,

2 shows a schematic representation of a collecting electrode coupling device,

Fig. 3 is a section along the line 3-3 of Fig. 2 and

4 shows another embodiment of the collecting electrode coupler.

A focused electron beam is generated. These electrons can continuously from one suitable electron generator, for example a heating wire, are emitted. The electrons will accelerated by suitable electric fields to a relatively high potential and to a Beam parallelized. This electron beam is then speed-modulated, for example by Change in electric fields to create a clumped or collimated electron beam which has periodic electron density changes. The bundled electron beam is then used to generate electromagnetic energy, for example in such a way that the beam moves in-with Traveling field linear acceleration of working electron accelerators

Applicant:

Richard F. Post,

Walnut Creek, Calif. (V. St. A.)

Representative:

Dr.-Ing. H. Ruschke, Berlin-Friedenau, Lauterstr. 37,

and Dipl.-Ing. K. Grentzenberg,

Munich 27, patent attorneys

Richard F. Post, Walnut Creek, Calif. (V. St. Α.), Has been named as the inventor

other is sent through one or more trapping resonance cavities, thereby exciting them will. The electromagnetic radiation is used to deflect a small part of the collimated beam to accelerate and bring back energy to it, so that a resulting high-voltage electron beam is produced.

In the first parts of the above process a stress doubling effect is created, whereby determined relatively few electrons in the collimated beam, essentially twice the speed or voltage of the remaining electrons by passing them through the collecting cavity 180 ° out of phase with the phase of the vibrations driven in the cavity get lost. These voltage doubling electrons are used for post-acceleration chosen. After the electromagnetic energy is generated by the bundled beam, the The beam is influenced in such a way that its beam flow cross-section is significantly reduced. Since the main part of the Tries to unbundle itself in the process of producing electromagnetic energy, distinguishes the collimation of the beam in favor of the voltage-doubled electrons.

Besides parallelizing the beam, the electromagnetic energy waves are along the beam path directed to bring energy back to the ray. So that the beam from the electromagnetic Waves is accelerated, becomes their phase

103 740/464

with reference to the voltage-doubled electron electron generator 16 and anode 17 placed that the beam pulses changed or vice versa, being negative in electron generator with respect to the anode this connection is certain of various kinds. Made by accelerating electrons driving steps are possible. A continuous electron tigen is used to achieve the righteous generator Phase relationship can either be the phase of the 5 ray formed. This ray passes through the electromagnetic waves against the beam impulses anode opening and thus through a pre-or lag behind. Advancing the phase of the bulging or bundling cavity 18 associated with the Magnetic waves can be achieved by aligning generators and, for example, for excitation that the energy waves and the electron beam through an externally applied time-varying high one Hollow line can be sent, the wave frequency voltage being suitable. The electron beam speed is substantially equal to or greater by this tension in the bundling cavity is the speed of light, while the Elekraum 18 modulates the speed in the usual way, electron beam speed is much smaller, so that in so that the electron beam after traversing a a predetermined distance a desired distance beyond the cavity 18 relatively Phase lead is reached. The lag of the 15 field-free space with periodic changes in the Energy wave phase can be achieved by bundling electron density. Behind the Bündedie Energy waves and the beam through a corrugation cavity 18 is followed by a second cavity 21, the deceleration device be steered, in which the first by an elongated through-shaft speed is connected to less than the beam path 19 through which the electron beam speed is reduced and in which one runs 20. The second cavity 21 is designed so that Orbit Distance adjusted the relative phase to that that it was in at the frequency of the collimated beam desired relationship shifts. Although both resonate, so that in the usual way a Resoobigen Possibilities can be carried out, there is an exchange of energy within the cavity 21 a smallest path length of the beam and the wave takes place, whereby electromagnetic energy in it either from slow wave propagation or 25 arises.

the propagation of the wave at a speed. The elements described above and the working

speed greater than the speed of light, as there are wise in such tubes as a klystron

in both cases a common practice brought to the maximum, but the electron beam is common

speed difference between the shaft and through a collecting electrode beyond the output

the beam is reached. Around this process- 30 hollow space 21 collected, the inside of the tube

step, it is necessary that one developed high frequency energy other devices,

makes use of the achievement of the minimum distance. for example by coupling loops or the like., for

There are still certain advantages here. Use in these is fed. The establishment

The acceleration of the voltage-doubled according to the invention transports the electron beam

Part of the bundled beam is thereby reached, 35 and the high-frequency energy from the tube and

that traveling voltage waves through the originally has a collecting electrode for this purpose

electromagnetic wave coupler 22 generated by the beam in axial alignment with tube 11

are produced and the beam this in a suitable manner, which is connected to the output cavity 21 in connection

Phase goes through. The appropriate phase relationship is in place. The collecting electrode coupler 22 includes the

is generated in the above-mentioned manner so that the 40 cylinders 14 and an inner member 23, which as

produced tension waves the tension doubling cylinder or solid body of revolution shown

accelerate the electrons of the beam. which, as shown, has an axial passage,

With the above procedure, a high voltage becomes similar to an inverted venturi, with a

Electron beam with periodically changing diameter, which changes with distance

Generated electron density. The 45 of the cavity 21 reduced in the process and an enlarged

The original electron beam used has a large opening at its exit. The element 23

small part of the energy actually supplied in order to, as shown in Fig. 1, for example by

to drive them to a high voltage. This will be a pair of quarter wave stubs 24 within the

by generating electromagnetic energy from cylinder 14 to ensure the insulation

the beam and then by returning them to 50 problems as much as possible. One

reaches a selected part of the beam. small opening through it serves to catch

Various structural arrangements can and collect a large part of the electron tube 11 coming from the electron tube used to carry out the described method. Getting inside; In Fig. 1, a preferred device half of the tube 11 experiences a certain small part is shown. A velocity-modulating electrode 55 of the electrons in the beam of an additional electron tube 11 is axially aligned with the waveguide of a traveling acceleration on essentially the double chip field linear accelerator 13 and is connected to the rest of the beam electrons, namely through an intermediate cylinder because their phase is such that they are related to the. The electron tube 11 can be accelerated out of the output cavity 21 and not hesitated with a conventional high-frequency electron beam tube 60. These electrons are made up of a klystron, for example, and are called an elec- tron with double speed. The particle electron beam system 16 with a filament and a voltage-doubled electrons will preferably have heating devices for this in order to generate free electrons for additional acceleration, since electrons are shown inside the tube. The elec- tron can be that an enlargement of the push-on tron from the electron generator 16 is accelerated by voltage the efficiency of the traveling field accelerator anode 17, which increases as a transverse tube wall and simplifies its structure,
is formed with an opening for the passage of electrons from within the collecting electrode coupler 22 according to. There will be such a voltage between Fig. 1, the radio frequency energy migrates from the

Tube 11 with the speed of light between the solving the relationship (1) for L , then results

Cylinder 14 and element 23, while even:

Electrons at double the speed driven by χ d. η

run the axial passage of the element 23, L = -. (2)

have a much slower speed so that the 5 2 B _g - B _e

Energy waves lead in phase with respect to the clustered electrons of the beam. The phase velocity of the wave is essentially the same as the speed of light in free space when given by the collecting electrode coupler. By suitable choice of the coupling wave so that B _g = 1; in a typical case of the energy waves rushing in phase exactly around the io 300,000 electron volts, B _e = 0.8, so that from the appropriate value with reference to the above relationship it follows that L = 2 A ₀ ; in a typical clusters of voltage-doubled electrons, velocity-modulating electron tube, as set out below. Inside the accelerator - a klystron, in which the wavelength is 10.5 cm waveguide 13 is a number of transverse partition walls 26, which openings on the waveguide 15 L = 21 cm. axis and limit a loaded waveguide, which consists of a number of successive Although the above determined length of the collecting cavities 27 of suitable dimensions is not undesirably large around the electrode coupler, an electromagnetic wave can be reduced with the exact same construction, phase velocity to propagate and on this 20 as shown in Fig. 2 and 3 is shown. Way to accelerate the pressed electrons with the frequency. The modified embodiment according to FIG. 2 of the energy, which is transferred to it by the and 3 illustrates a collecting electrode coupling tube 11 via the collecting electrode coupler 22 and 31, which has a cylinder 14 to which the coupling is coupled . In this way, a traveling wave is produced in the acceleration between the output cavity 21 of a niger 12, which its tube 11 and the waveguide 12 of the niger absorbs energy from the tube 11 and produces energy at gers 13. Coaxially within this cylinder 14 emits electrons, a cylindrical element 23 is arranged in a suitable phase relationship, which extends through it. As noted above, structure denoted by the same reference number corresponds to the appropriate choice of the length of the collecting element in FIG. 1, but being shorter, electrode coupler 22 having electrons with double 30 as discussed below. In this embodiment, a coaxial fundamental mode of oscillation at each cavity is excited so that only clusters of electrons at the end of the coupler due to a special waveguide voltage doubled electrons are reversed in the middle part of the coupler. The collecting electrode coupler 22 acts in a shaping manner. Thus, at each end of the coupler 31, and thus for part of the electrons as trapping 35, the surrounding cylinder 14 are symmetrical, so that the element in the tube 11, while at the same time allowing the electric field of the emitted electromagnetic passage of part of the beam and also table waves radially outward from the coupler coupling the tube energy into the waveguide 13 in order to excite the cavities 27 thereof axially and uniformly across the element 23. will. This coaxial mode of operation of the transmission is the part of the 40 accelerated in the waveguide 12 due to its axial symmetry for coupling out of the electron beam outside the device into the cavity 21 and coupling into the acceleration by creating a window 28 on the lower 13 particularly useful. The middle part of the closed end of the waveguide at its axis coupler 31 will be used by a wall or a sink. The window seals in spite of its right element carried (as in Fig. 2 and 3 represents the permeability for the accelerated electron 45), which radiates parallel to the axis and below the system vacuum-tight, which for the ar- the waves between the cylinder 14 and the EIebeitweise is necessary. ment 23 runs. This wall 32 actually comprises, with respect to the phase change of the electrical part of the coupler 31 formed by the cylinder 14, magnetic waves and the electrons with double element 23 and the wall 32, insopelter velocity of the beam it is in the prior 50, as the transmitted electromagnetic waves direction of the type described above are desired that are affected, since the fundamental mode of the phase of the energy waves is changed by 180 ° (π radians) with wave transmission so that reference to the phase of the Electrons with double this takes place at the circumference, whereby the wave speed is shifted. With the above speed the speed of light exceeds. Small written coaxial collecting electrode couplers according to 55 vertical bolts or rods 33 are on the Zy-Fig. 1, which has a length L , the following relation applies below the element 23 at each end for 180 ° phase shift: its wall 32 for impedance matching between the

coaxial fundamental mode and the waveguide

-Z ^. = π. (1) vibration type arranged and are usually

Be A ₀ Bg A ₀ 6o referred to as adapter bolt. Although the adapt

bolts serve an embodiment of the invention

A ₀ = wavelength of vibration generated in the manure, those skilled in the art will free space at operating frequency various other means of achieving the same

B _e = speed of the electron beam, results must be familiar.

drew on the speed of light (c) in the 65 In the embodiment of Figs. 2 and 3, in the

free space the wave speed in the middle section

Bg = phase velocity of the wave, related to coupler which exceeds the speed of light, can be the speed of light (c) in free space. is the length L of the central portion where the wall 32

appropriate to be determined from the following relationship:

2nL 2nL _

Be A ₀ Bg A ₀

where all symbols correspond to those defined above. So is

A ^ (4)

2 Bg - Be

as in the embodiment in Fig. 1. However, in this case, the phase velocity of the wave determined in the middle section by boundary conditions for the fundamental transmission mode, the can be expressed as follows:

γ Λ)

is again equal to the phase velocity of the wave, based on the speed of light, with a ratio of the disk diameter to the diameter of the element 23 of about 1.5 to 1 and a ratio of the cylinder diameter to the diameter of the element 23 of about 1.7 to 1 can be achieved. The relationship given with reference to FIGS. 1 and 2 can be used here again with a difference in sign, since B _{e is} greater than B _g , so that

2nL

Bg A ₀ B _e A ₀

= π

and

sin (K ₂ P) = 0 or Jf ₂ =

B _e 'Bg

Be - Ba

(5; 5a)

where P is the mean circumferential dimensions and
Κι + KS = K ^z (6)

means where K = - ^ - and K ₁ =
Solving (6) for B ₉ results

2Λ

are.

2p

and in a typical case where the diameter of the element 23 is 2.5 cm, the cylinder diameter 3.5 cm unap = 7.0 cm, with X ₀ = 10.5 cm and B _e = 0.8, such as above, B ₉ = 1.60.

Inserting this into equation (4) for L results in the value 0.8 or 8.4 cm. This dimension of 8.4 turns out to be much smaller than the length of 21 cm calculated above for a typical construction of the embodiment according to FIG . 1.

Another embodiment of the coupler is illustrated in FIG. 4. In this an element 23, which is essentially identical to the element in FIG. 1 except for the size, is arranged in a cylinder 14 between the tube 11 and the accelerator 13, for example by quarter-wavelength stubs 24. In this example, a special construction is provided within the coupler 34 formed by the above-mentioned elements in order to create a periodically loaded coaxial section and in this way to retard the phase of the wave with respect to the electrons. Such a construction is well known for its slow wave propagation properties and in the illustrated embodiment a number of radial flanges or washers 36 are provided on the coupler and are evenly spaced along the outer surface of the coupler. Since the wave is propagated between the cylinder 14 and the central element 23, the disks form such a periodic construction that the wave speed is substantially reduced. Within practical limits, the wave speed can be made as small as desired and, for example, a value of B ₉ = 0.5, where B ₉ here is set B ₉ = 0.5 and B _e = 0.8 in the above relation , then L = 0.67 X ₀ , so that at X ₀ = 10.5 cm L = 7 cm. In this case , as in the embodiment of FIG. 2, L is taken as the length of the central periodic portion of the coupler 34 so that the unloaded end portions must be added to determine the total length.

There has been described an improved method and apparatus for electron acceleration but a single source was used to generate a pulsating electron beam and Generate energy for its acceleration. The illustrated and described embodiments of the coupler are only to be considered as examples. In particular, the calculations should only be used as examples and in no way the To limit the scope of the invention as outlined in the following claims.

Claims (14)

PATENT CLAIMS: 1. With traveling-field linear acceleration working electron accelerator, consisting of an electron source in the form of a speed-modulated electron tube, which delivers a bundled, density-modulated electron beam, and a traveling field linear accelerator and a coupling device bringing these two parts together, characterized in that the coupling device has both high-frequency energy and Generated electrons of high energy, the high-frequency energy as a voltage traveling wave causing further accelerations of the electrons in the traveling field linear accelerator. 2. Electron accelerator according to claim 1, characterized in that the coupling device acts as a waveguide that it has a narrow central channel for parallelizing the electron beam has and that it is made comparatively long. 3. Electron accelerator according to claim 1 or 2, characterized in that means are provided are to determine the phases related to the length of the coupling device Amplitudes of the radio frequency energy and certain electron densities of the density modulated Adjust the electron beam so that the points of certain density of the electron beam accelerated by the high frequency energy. 4. Electron accelerator according to one of the preceding claims, characterized in that that in the housing (14) of the coupling device coaxially arranged means (23) are provided in which there is a small opening that is used by the tube sent into the waveguide Electrons limited. 5. Electron accelerator according to one of the preceding claims, characterized in that that the waveguide has centrally pierced transverse partitions (26) through the resonance cavities (27) are formed, which are connected to one another through the central openings of the partition walls are. 6. Electron accelerator according to claim 1, characterized in that the traveling field linear accelerator a housing (12), the axis of which corresponds to the electron beam emerging from the tube is axially aligned. 7. electron accelerator according to claim 1 or 6, characterized in that the coupling device one aligned coaxially with the axis of the electron source and the linear accelerator Has component (23), which the electromagnetic energy of the tube in the accelerator (13) is coupled in, and the electron beam from the tube through its narrow axial opening is parallelized before entering the accelerator. 8. Electron accelerator according to claim 7, characterized in that the coupling device has a length sufficient to change the phase of the electromagnetic energy 180 ° to make the phase of the collimated electron beam adjustable to lead or lag. 9. electron accelerator according to claim 4, characterized in that the coaxially arranged Device (23) is mounted on the housing (14) by a radially extending element (32) and has a predetermined length which enables the wave propagation speed to be the Exceeds the speed of light. 10. Electron accelerator according to claim 7, characterized in that the coaxial element having axially spaced radial disks (36) which load this element. 11. Electron accelerator according to claim 1, characterized in that the tube is a klystron having an open ended exit cavity axially aligned by a cylinder a waveguide is coupled. 12. Electron accelerator according to claim 11, characterized in that the coupling device is cylindrical and is arranged in said cylinder, the coupling device has a tapered axial passage to hold only a small fraction of the electrons from the klystron, and has a length to reflect the phase shift between the energy radiated through by the klystron and the bundled electrons passing through so to be able to adjust that the electrons are accelerated or decelerated. 13. Electron accelerator according to claim 1, characterized in that the coupling device comprises an elongated tube adapted to surround the waveguide and the tube exit to connect, as well as a coupling cylinder, the coaxially within the elongated Tube is arranged, which has a limited connection between the electron tube and the Manufactures waveguides. 14. Electron accelerator according to claim 13, characterized in that the coupling cylinder has gently curved, convex inner walls having. Considered publications:
Rev. of. scient. Instrum., 26 (1955), pp. 205-209. 1 sheet of drawings © 109 740/464 11.61