JPH03173492A - Free-electron laser device using linear type accelerator - Google Patents

Abstract

PURPOSE:To improve the efficiency of energy recovery by arranging a fan- shaped electromagnet, simultaneously deflecting and distributing two electron beams and combining an accelerating tube and a decelerating tube while properly constituting the distance of transfer of beams. CONSTITUTION:Electron beams emitted from an injector 11 are accelerated by an accelerator 13, and projected to a wiggler system by a fan-shaped deflecting electromagnet 15 and a rectangular deflecting electromagnet 16. The direction of electron beams emitted from the wiggler system is bent at 180 deg. by two deflecting electromagnets 20, and the electron beams are projected to the electromagnet 15 from the reverse side again through a rectangular deflecting electromagnet 21, and placed on approximately the same orbit as outgoing. The electron beams are moved backward in decelerating phase to the accelerating tube 13 by properly organizing the distance of transfer of beams in the constitution, and RF resonance is intensified while losing kinetic energy through interaction with an RF electric field. The electron beams decelerated and emitted from the tube 13 are introduced to a beam collector 22 through an electromagnet 22, and terminated. Accordingly, energy can be recovered efficiently, thus acquiring a large output.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an industrial free electron laser device, which is intended for use in spectroscopic analysis of material compositions and photoexcitation reaction processes in the industrial chemistry, pharmaceutical, and medical fields. In particular, the present invention relates to a structure that enables effective energy recovery.

(Conventional technology) In recent years, the use of electromagnetic waves has expanded beyond basic research to include measurement and inspection equipment, processing, and production equipment such as reaction devices. , is rapidly increasing. In particular, lasers, as powerful monochromatic coherent light sources, have brought about numerous technological innovations in various types of spectroscopic analysis, measurement, and processing. However, since conventional lasers are a type of amplifier that utilizes stimulated radiation during transitions between electronic levels in atoms, molecules, or solids, they have the disadvantage that they can only obtain electromagnetic waves with a fixed oscillation wavelength unique to each medium. there were. In particular, lasers with short wavelengths below the ultraviolet region have not yet reached the practical stage because a medium with an appropriate level that can ensure sufficient gain for this wavelength has not been discovered.

Also, since laser oscillation basically relies on a mechanism that transmits it through a gas or solid medium and amplifies it,
There are problems with cooling and damage to the medium, and there is a limit to the output. Dye lasers, which are organic liquid lasers, have the advantage of being wavelength tunable within a certain range, but for the same reason, practical output has not been achieved.

Some lasers are used for laser processing, photochemical reactions in the field of new materials, and laser fusion, in the field of nuclear power.
Isotope separation is at a proven level in the medical and biological fields, such as surgery and bioinstrumentation, but it has spread to a wide range of stress fields. Short wavelength region is also possible, (b) high output, (C)
The emergence of a new laser light source that can meet the demand for high efficiency is awaited.

In response to this trend, free electron lasers have a different oscillation mechanism from the conventional laser method described above, and are synchrotron radiation generated when a high-energy electron beam meanders in a Wiggler magnetic field.
ron radiation) and the effect of its electromagnetic waves modulating the density distribution in the direction of electron propagation, which causes a kind of resonance phenomenon, resulting in a kind of stimulated radiation effect. There is a possibility that In this case, the oscillation wavelength is proportional to the wiggler period and inversely proportional to the square of the energy of the electron beam, so it has the advantage that any wavelength can be obtained by selecting an appropriate accelerator and setting operating conditions.

Furthermore, the output at saturation is proportional to the electron current value, and since electromagnetic waves propagate in vacuum space, there is no limit to the output in principle. Due to these characteristics, it is expected to be used as a next-generation industrial light source, and development is progressing.

Among these, free electron lasers using linear accelerators (RF linacs) have high beam quality (low emittance) and can obtain high energy (~GeV) with relatively simple equipment, making it possible to achieve submillimeter lasers. It is expected that it will be used to realize highly efficient free electron lasers in the ultraviolet to ultraviolet wavelength range. As an example, Japanese Patent Laid-Open No. 56-124282 discloses a free electron laser system having a basic configuration as shown in FIG. FIG. 3 shows an equipment configuration layout diagram that embodies this. The electron beam emitted from the injector (I) is sent to the RF power source (3) at the high frequency accelerator tube (2).
After being accelerated, the energy is analyzed by a 60° bending electromagnet (4), enters a wiggler electromagnet (5), and contributes to laser oscillation. The electron beam that has finished its role is 18
It is guided to a deceleration tube (7) by a 0° bending electromagnet (6) and the like, and the kinetic energy is converted into RF energy and decelerated, and then recovered by an end station (8).

The RF energy recovered by the decelerator is transferred to the coupler (9)
The beam is then returned to the accelerator (2) and contributes to beam acceleration again. Reflecting mirrors θ0) are placed before and after the wiggler. This free electron laser obtains a beam current of several A and has a beam current of 100
We have successfully achieved oscillation of ~800 μm.

(Problems to be Solved by the Invention) The free electron laser using the conventional linear accelerator shown in FIGS. 2 and 3 has the following drawbacks.

(A) Two adding (decreasing) connecting pipes, an acceleration pipe (2) and a deceleration pipe (7), are required.

In a normal acceleration cavity, 8 of the applied RF energy
More than 0% is dissipated as heat on the tube wall. A similar thing happens with reduction tubes, where most of the energy converted to RF becomes heat. Due to these factors, energy recovery efficiency is extremely poor.

(B) The recovered energy is returned to the accelerating tube (2) through the coupler (9), but a portion of the RF is reflected by the coupler, resulting in a poor energy recovery rate.

(Means for Solving the Problems) In order to solve the problems of the prior art, the present invention provides a free electron laser with a configuration that can improve the efficiency of energy recovery.

Therefore, in the free electron laser device using the linear accelerator of the present invention, in the free electron laser device using the linear accelerator as the electron beam source, (I) the trajectory of the electron beam emitted from the injector and the wiggler electromagnet In order to share one acceleration tube with the trajectory of the recovered electron beam after passing through the electron beam, fan-shaped deflection electromagnets are installed before and after the acceleration tube to simultaneously deflect and distribute these two electron beams. , (II) R of the accelerator tube
For F excitation, the beam transport distance is arranged such that the bunches of electron beams emitted from the injector enter the acceleration tube in an acceleration phase, and the collected electron beam bunches returning from the wiggler enter the acceleration tube in a deceleration phase. It is characterized by:

(Function) In the present invention, one accelerating tube can be used for both acceleration and deceleration, that is, it has the functions of accelerating the electron beam before entering the wiggler and decelerating and recovering the electron energy that did not contribute to the laser oscillation. Since the heat loss at the tube wall can be reduced to 172 compared to the conventional method. Furthermore, since the recovery side electron beam acts directly on the excitation in the accelerator tube without the need for a coupler, energy recovery efficiency is greatly improved.

In particular, when a superconducting accelerator tube is used, nearly 100% of the energy can be recovered, making it possible to achieve conversion efficiency comparable to that of a storage ring.

Therefore, a highly efficient free electron laser device can be realized.

(Example) Hereinafter, the present invention will be explained in more detail with reference to an example shown in FIG. FIG. 1 is a structural layout diagram of an embodiment of an optical klystron type free electron laser using a one-stage linear accelerator.

In this embodiment, the electron beam emitted from the injector θD is deflected by the first fan-shaped bending electromagnet 0, and enters the high frequency linear acceleration tube 03) in the acceleration phase, where it is powered by the RF power source 0. After being accelerated, the second fan-shaped bending electromagnet 05) and the rectangular bending electromagnet 0ω,
It is placed in Wiggler orbit.

In this example, the Wiggler system is an optical talistron (
Considering the K lys tron) method, the modulator
It consists of a magnetic surface and a helical or planar wiggler magnet 08). The synchrotron radiation generated here
n) is amplified while reciprocating between the Fabry-Perot type resonators formed by the two reflecting mirrors 09), and is emitted as a laser beam output from the reflecting mirror that does not perform total reflection.

The collected electron beam that has exited the wiggler is bent by 180° by 2[D, passes through the rectangular bending magnet (21), and then enters the second fan-shaped bending magnet 05 from the opposite side. The acceleration tube 03) is bent and placed on almost the same trajectory as at the time of ejection, and this time in the deceleration phase.
trace back. As the electron beam travels back through the accelerating tube, it interacts with the RF electric field, losing kinetic energy and strengthening the RF resonance. The electron beam that has been decelerated and exits the accelerator tube passes through the first fan-shaped bending electromagnet and is then sent to the beam collector (22).
It is guided and terminated. (23) is a beam focusing quadrupole lens placed in the beam path.

As described above, in the present invention, with respect to RF excitation for acceleration control, the bunch of electron beams emitted from the injector (I) is in the acceleration phase, and the bunch of electron beams returning via the wiggler is in the deceleration phase and has the same acceleration. The beam is arranged at a certain distance so that it is incident on the tube.

In the above embodiments, the bending electromagnet with sector-shaped magnetic poles is used because it has a typical shape in which two symmetrical orbits can enter and exit perpendicularly, and the present invention does not particularly limit these geometric shapes. This is because vertical input/output does not generate quadrupole magnetic groups near the edges, making system design easier.

(Effects of the Invention) As described above, in the free electron laser device using a linear accelerator according to the present invention, a high-output laser beam can be obtained at any wavelength, and one accelerator tube can be used commonly for acceleration and deceleration. This makes it possible to reduce the loss of beam energy, increase the recovery rate, and achieve high efficiency.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a free electron laser device using a linear accelerator according to an embodiment of the present invention, Figure 2 is a diagram showing the basic configuration of a conventional free electron laser system, and Figure 3 is a specific equipment configuration. A layout diagram is shown. (I)...Injector, (2)...High frequency accelerator tube, (3)...RF power supply, (4)...60° bending electromagnet, (5)...Wiggler electromagnet, (6) ...1
80° bending electromagnet, (7)...reduction tube, (8)...
End station, (9)...Coupler 00)・
... Reflector, (I1) ... Injector, 02)
・・First fan-shaped bending electromagnet, surface・High frequency linear accelerator tube,
En...RF power supply, 05)...Second sector-shaped bending electromagnet,
0 (21)...Rectangular bending electromagnet, 07]...Modulator magnet, 08)...Wiggler magnet, 09)...Reflector, Qt...180' deflection magnet,
(22)... Beam collector, (23)... Quadrupole lens for beam focusing.

Claims (1)

[Claims] In a free electron laser device using a linear accelerator as an electron beam source, (I) the trajectory of the electron beam emitted from the injector and the trajectory of the recovered electron beam after passing through the wiggler electromagnet, In order to share one accelerating tube, fan-shaped deflecting electromagnets are installed before and after the accelerating tube to simultaneously deflect and distribute these two electron beams. Energy recovery characterized in that the device is arranged such that the beam transport distance is such that the bunch of electron beams emitted from the wiggler enters the accelerating tube in the acceleration phase, and the bunch of recovered electron beams returning from the wiggler enters the accelerating tube in the deceleration phase. A free electron laser device using a type of linear accelerator.