JPH0676990A - Optically controlled accelerator system - Google Patents

Abstract

PURPOSE:To efficiently generate a highly uniform electron beam by accurately synchronizing electron emission from the photoelectric surface of an electron gun with the application of high frequency electric field for electron acceleration without causing any phase deviation, using an optical signal and an optical means. CONSTITUTION:A periodical pulse train generated with a laser oscillator 110 is branched into two via a divider 151 comprising a half-mirror or the like, and one of the train is irradiated to the photoelectric surface 131 of an electron gun body 130 through an optical retarder 161. The other pulse train is multiplied with a pulse multiplexor 170 comprising a mirror, a half-mirror group or the like for irradiation to the photoelectric surface 121 of a microwave generating device 120. As a result, a microwave generated via the excitation of an electric field generator 122 with electrons emitted from the surface 121, is transmitted to an electron gun 130 via a waveguide 140, and electric field is applied thereto in a high frequency acceleration cavity 130. An electron group from the surface 131 is thereby accelerated and emitted. According to this construction, electron emission and electric field application can be accurately synchronized with each other without any phase deviation, and an electron beam having good uniformity and high energy can be efficiently generated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electron accelerator systems used to obtain high energy electron beams.

[0002]

2. Description of the Related Art A group of electrons generated by colliding an electron group, which moves at almost the same speed as light, with a target is observed to study the basic law of nature. In order to obtain electrons that move at almost the speed of light, it is necessary to take out the electrons existing in the substance and accelerate them. Conventionally, as an accelerator system used for this purpose, a system as shown in FIG. 3 is known in which an electron beam and a periodic electric field generated in an accelerating cavity are synchronized by a high frequency electric signal.

In this electron accelerator system, a reference frequency oscillator 210 for generating a reference high frequency electric signal, a frequency divider 220 for dividing the reference high frequency electric signal, and a laser oscillator 230 driven by an output signal of the frequency divider 220. A photocathode 131 that receives the pulsed light emitted by the laser oscillator 230 and emits electrons, and an electron gun 130 having a high-frequency acceleration cavity 132 that accelerates the electrons, and a phase that adjusts the phase of the reference high-frequency electrical signal. A shifter 240 and an RF amplifier 250 for amplifying a phase-adjusted high frequency electric signal
And a klystron 260 that is driven by the output signal of the RF amplifier to generate a microwave, and a waveguide 270 that transmits the microwave to the high-frequency acceleration cavity.

In this electron accelerator system, the timing of system operation is generated based on the high frequency electric signal generated by the reference frequency oscillator 210. The photocathode 131 of the electron gun 130 is irradiated with laser light obtained by driving the laser oscillator 230 with a pulse signal obtained by dividing the high frequency electric signal generated by the reference frequency oscillator 210 by the frequency divider 220. The group of electrons emitted into the accelerating cavity is obtained by the photoelectric effect. The electron group thus obtained is accelerated by the high-frequency electric field applied to the high-frequency acceleration cavity 132, and emitted from the electron gun 130 as an electron flux having substantially the same energy and momentum for each electron.

At this time, the electric field applied to the high frequency acceleration cavity 132 needs to be synchronized with the emission of the electron group from the photocathode 131. To this end, the reference frequency oscillator 210
The electric signal generated by is adjusted in timing by the phase shifter 240 to drive the klystron 260, which is a high-frequency signal generator, via the RF amplifier 250. The high-frequency signal thus generated is transmitted via the high-frequency coupler of the electron gun 130 via the waveguide 270, and an electric field for electron acceleration is generated in the high-frequency acceleration cavity 132 in synchronization with the above-mentioned electron group emission. The phase shift amount of the phase shifter is adjusted to accelerate the electron group at the optimum synchronization timing.

[0006]

In the conventional electron accelerator system, in order to accurately synchronize the emission of electrons from the substance and the application of the high frequency accelerating electric field to the accelerating cavity by the above method, the high frequency is required. A high-frequency electric circuit such as a signal frequency divider and a phase shifter must have a complicated structure. The complication of these circuits inevitably resulted in a phase shift of the generated acceleration electric field and a lack of operational stability due to the jitter of each circuit. Further, the complicated high frequency circuit group causes an increase and complexity of a control system for controlling them, resulting in an increase in cost.

In particular, the phase shift of the accelerating electric field due to the jitter of each circuit element causes a large spread in the energy distribution of each electron of the electron group after acceleration. The non-uniformity of electron energy in this electron population results in an increase in unaccelerated electrons. Further, in the application of the free electron laser, the laser gain of the laser resonator is significantly reduced. In order not to cause these efficiency reductions, it is necessary to suppress the phase deviation of the accelerating electric field to 10 psec or less, but in the conventional method using an electric signal,
Achieving this deterrence was difficult with the current technology.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an accelerator system that efficiently produces a high-energy electron beam with good energy uniformity.

[0009]

SUMMARY OF THE INVENTION An optically controlled accelerator system according to the present invention synchronizes extraction of electrons existing in a substance and application of a high frequency electric field to a high frequency accelerating cavity for accelerating electrons with an optical signal and an optical signal. It is intended to be realized by using optical means.

Specifically, one optical control accelerator system of the present invention comprises a laser light source which generates a periodic pulse train, and a branching means which generates two optical pulse trains of the same timing from the optical pulse train generated by the laser light source. An optical delay means for delaying one of the output optical pulse trains of the branching means with time, a first photocathode that receives the optical pulse train through the delay means and emits electrons, and accelerates the emitted electrons. An electron gun having a high-frequency accelerating cavity, a pulse multiplexing means for shortening the other pulse period of the output light pulse train of the branching means, and a multiplexed light pulse received through the pulse multiplexing means to emit electrons. And a microwave generator having a second photocathode for accelerating the emitted electrons to generate microwaves, and a microwave generated by the microwave generator is applied to the high frequency application of the electron gun. Characterized in that it comprises a waveguide which transmits the cavity, the.

Another optical control accelerator system of the present invention is a laser light source for generating a periodic pulse train, and a first branching means for generating two optical pulse trains at the same timing from the optical pulse train generated by the laser light source. A first optical delay means for applying a time delay to one of the output pulse trains of the first branching means, a first photoelectric surface for receiving an optical pulse train through the delay means and emitting electrons, and the emission. An electron gun having a first high-frequency accelerating cavity for accelerating electrons, a pulse multiplexing means for shortening the other pulse period of the output light pulse train of the first branching means, and a multiplexing light output by this pulse multiplexing means Second branching means for generating a predetermined number of multiplexed optical pulse trains from the pulse train, and second optical means for individually delaying each multiplexed optical pulse train output from the second branching means. delay A plurality of microwave generations that have a step and a second photocathode that emits electrons by receiving the multiplexed light pulse through the second optical delay means, and accelerates the emitted electrons to generate microwaves. An apparatus, one or more accelerating tubes having a second accelerating cavity that directly or indirectly communicates with the first rf accelerating cavity, and microwaves generated by each microwave generating apparatus are accelerated by the first high-frequency accelerating apparatus. The same number of waveguides as the microwave generators that individually transmit the cavities or the second high-frequency acceleration cavities are provided.
In this case, the number of microwave generators is equal to the number of electron guns plus the number of accelerator tubes.

[0012]

In one light control accelerator system of the present invention, the periodic light pulse train generated by one laser light source is used as a reference for synchronizing the accelerator systems. This reference optical pulse train is split into two optical pulse trains with the same timing, and one optical pulse train is time-delayed by the optical delay means to generate an optical pulse train for irradiating the photocathode of the electron gun with the other optical pulse train. Is reduced by a pulse multiplexing means to generate an optical pulse train for irradiating the photoelectric surface of the microwave generator. The microwave generator generates a microwave having the same period as the light pulse period with which the photocathode is irradiated. This microwave is transmitted through the waveguide to generate an accelerating high frequency electric field in the high frequency accelerating cavity in the electron gun. The timing of electron emission from the photocathode of the electron gun and the high frequency electric field for high frequency acceleration cavity electron acceleration can be accurately synchronized by adjusting the delay time of the optical delay means.

In another light control accelerator system according to the present invention, a periodic pulse train generated by one laser light source is used as a reference for synchronizing the accelerator system. This reference oscillation pulse train is branched into two pulse trains having the same timing by the first branching means, and one pulse train is optically delayed by the first optical delaying means to irradiate the second photocathode of the electron gun. The optical pulse train is generated, and the other pulse train is generated by the pulse multiplexing means to generate a multiplexed pulse train whose period is shortened. The multiplex pulse train is generated by the second branching means to generate the same number of pulse trains as the multiplex pulse trains as the number of microwave generators. A different optical delay is given to each of the plurality of pulse trains thus obtained by the second optical delay means, and an optical pulse train for irradiating each first photoelectric surface is generated. A microwave having the same period as the light pulse period applied to the first photocathode generated by the microwave generator is transmitted through the waveguide, and a high-frequency electric field for acceleration is transmitted to the second high-frequency acceleration cavity in the electron gun. It is generated in the third high-frequency acceleration cavity in the acceleration tube. The timing of electron emission from the second photocathode of the electron gun and the high-frequency electric field for electron acceleration can be accurately synchronized by adjusting the delay times of the first and second optical delay means. In this system,
It is possible to further accelerate the accelerated electron group emitted by the electron gun.

As described above, in the photo-controlled accelerator system according to the present invention, since the synchronization is performed by the optical signal and the optical means, extremely accurate synchronization is possible and the electrical signal and the electric signal are obtained. It is possible to avoid a large phase shift that necessarily occurs in the means.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a block diagram of an optically controlled accelerator system according to the first embodiment. What is characteristic of this optical control accelerator system is that it has a basic signal for timing control of the accelerator system. It is configured to generate signals from a laser light source that generates one periodic pulse train, generate signals that need to be synchronized, and adjust timings between these signals by using an optical device.

This light control accelerator system comprises a laser light source 110 for generating a periodic pulse train, a branching device 151 for generating two optical pulse trains at the same timing from a light pulse train generated by the laser light source, and an output light of this branching device. An electron gun having an optical delay device 161 that delays one of the pulse trains, a photocathode 131 that emits electrons by receiving an optical pulse train through the delay device, and a high-frequency acceleration cavity 132 that accelerates the emitted electrons. 130, a pulse multiplexer 170 that shortens the other pulse period of the output optical pulse train of the branching device 151, and a photocathode 121 that receives the multiplexed optical pulse via the pulse multiplexer 170 and emits electrons. A microwave generator 120 that accelerates the emitted electrons to generate a microwave and a microwave generated by the microwave generator 120 Rf cavity 13 of the electron gun 130
2 and a waveguide 140 that transmits the light.

The periodic pulse train generated by the laser light source 110 first becomes two pulse trains of the same timing via the branching device 151 composed of a half mirror or the like. One of the pulse trains is converted into a pulse train for irradiating the photocathode 131 provided in the electron gun body 130 via the optical delay device 161 including a mirror group and the like. The other pulse train is a pulse multiplexer 1 including a mirror and a half mirror group.
The pulse repetition rate is multiplied by 70, and one multiplexed pulse train for irradiating the photocathode 121 provided in the microwave generator 120 is obtained.

When the photocathode 121 is irradiated with this pulse train light, electrons are periodically emitted from the photocathode 121. The emitted electrons are excited by passing through the electric field generator 122,
An electron beam is generated periodically to generate microwaves in the surroundings. This microwave is transmitted to the electron gun 13 using the waveguide 140.
0, and a high frequency acceleration electric field is applied in the high frequency acceleration cavity 132. The electron group emitted from the photocathode 131 is
It is accelerated by this accelerating electric field, is given a predetermined kinetic energy and a predetermined motion direction, and is emitted from the electron gun 130. In the above photo-controlled accelerator system, the generation of electrons and the application of the accelerating electric field are synchronized by processing the optical signal by an optical means. As a result, the problem of large phase deviation does not occur, and the synchronization can be achieved extremely accurately.

Next, the second embodiment will be described. FIG. 2 is a block diagram of the light control accelerator system according to the second embodiment. In this system, two accelerating tubes 180a and 180b are added to the system of the first embodiment,
High-frequency acceleration cavity 181 of each acceleration tube 180a, 180b
Microwave generators 120b and 120c that generate high-frequency electric fields for acceleration applied to a and b, and a half mirror that generates a multiplexed pulse train for microwave generation from one multiplexed pulse generated by the pulse multiplexer 170. Second consisting of etc.
Second optical delay device 162 including a branching device 152, a mirror and a half mirror, and the microwave generator 12
Waveguides 140b and c for transmitting the microwaves generated at 0b and c to the acceleration tubes 180a and 180b are added.

In this system, one multiplexed pulse described in the first embodiment is branched by the second branching device 152 into the same number of multiplexed pulse trains as the installed microwave generator. A different optical delay is applied to these multiplexed pulse trains by the second optical delay device 162 to generate pulsed light for irradiating the photoelectric surfaces 121a, b, c of the microwave generators 120a, b, c. It The microwave generated by each microwave generator 120 is transmitted to the high frequency acceleration cavity 131 of the electron gun 130 and the high frequency acceleration cavities 181a and 181 of the acceleration tubes 180a and 180b via the waveguides 140a, b and c.

In the above-mentioned photo-controlled accelerator system, since the generation of electrons and the application of the accelerating electric field are all synchronized by processing the optical signal by the optical means as in the first embodiment, the conventional electric signal is used. Compared with the synchronization in the accelerator system according to, the problem of large phase deviation does not occur, the synchronization can be achieved very accurately, and the accelerated electron beam obtained in the first embodiment can be further accelerated. It is possible.

The present invention is not limited to the above embodiment, but can be modified. For example, although the number of the accelerating tubes is two in the second embodiment, this accelerating tube may be one,
Also, it may be three or more. As the number of accelerating tubes is increased, a higher energy electron beam can be obtained.

[0024]

As described above in detail, according to the present invention, the electron emission from the photocathode of the electron gun and the application of the high frequency electric field for electron acceleration are synchronized by processing the optical signal with an optical means. Therefore, the problem of large phase blur does not occur,
The synchronization can be achieved very accurately, and the electron beam accelerated with good uniformity can be efficiently provided.

[Brief description of drawings]

FIG. 1 is a block diagram of an optically controlled accelerator system according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a light control accelerator system according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a conventional accelerator system.

[Explanation of symbols]

110 ... Laser oscillator, 120 ... Microwave generator,
121 ... Photoelectric surface, 122 ... Electric field generator, 130 ... Electron gun, 131 ... Photoelectric surface, 132 ... High frequency acceleration cavity, 140
... Waveguides, 151, 152 ... Branchers, 161, 162 ...
Optical delay device, 170 ... Pulse multiplexer, 210 ... Reference frequency oscillator, 220 ... Frequency divider, 230 ... Laser oscillator,
240 ... Phase shifter, 250 ... RF amplifier, 260 ... Klystron, 271 ... Waveguide.

Claims (3)

[Claims] 1. A laser light source that generates a periodic pulse train, a branching unit that generates two optical pulse trains at the same timing from an optical pulse train generated by the laser light source, and a temporal light output to one of the output optical pulse trains of the branching unit. An optical delay unit for delaying, an electron gun having a first photocathode that receives a light pulse train through the delay unit and emits electrons, and an RF gun for accelerating the emitted electrons; It has a pulse multiplexing means for shortening the other pulse period of the output light pulse train, and a second photocathode for receiving the multiplexed light pulse through the pulse multiplexing means to emit electrons and accelerate the emitted electrons. A microwave generator for generating a microwave and a waveguide for transmitting the microwave generated by the microwave generator to the high-frequency acceleration cavity of the electron gun. Light control accelerator system to be. 2. A laser light source that generates a periodic pulse train, a first branching unit that generates two optical pulse trains with the same timing from an optical pulse train generated by the laser light source, and an output pulse train of the first branching unit. A first optical delay means for applying a time delay to one side, a first photocathode that emits electrons by receiving a light pulse train through the delay means, and a first high-frequency acceleration that accelerates the emitted electrons. An electron gun having a cavity, a pulse multiplexing means for shortening the other pulse cycle of the output optical pulse train of the first branching means, and a predetermined number of multiplexed optical pulse trains output from the pulse multiplexing means. Second branching means for generating an optical pulse train, second optical delaying means for individually delaying each multiplexed optical pulse train output from the second branching means, and the second optical delaying means. Optics A plurality of microwave generators having a second photocathode that receives multiplexed light pulses via a delay means and emits electrons, and accelerates the emitted electrons to generate microwaves; One or more accelerating tubes having a second accelerating cavity that directly or indirectly communicates with the accelerating cavity; An optical control accelerator system comprising: the same number of waveguides as the microwave generators, which are individually transmitted for each high-frequency acceleration cavity. 3. The photo-controlled accelerator system according to claim 2, wherein the number of the microwave generators is equal to the result of adding the number of the accelerating tubes to the number of the electron guns.