JPH05251798A - Device and method for generating scattered beam of charged-particle beam excited-gas laser beam - Google Patents

Abstract

PURPOSE:To provide a small-sized scattered beam generator, which has simple structure and high safety to a malfunction, construction cost of which is reduced and which has high efficiency. CONSTITUTION:Accelerated charged particles are guided by the magnetic field of a coil for generating a guide magnetic field, propagated in an interaction tube 18 under a vacuum, and projected into a laser tube 17 by the magnetic field of a coil 6 for generating a pending magnetic field. Charged particles excite a laser gas medium by a collision, and oscillate a laser. Laser beams are transmitted in an output mirror 13, turned back by a reflecting mirror 14, projected onto the orbit of particle beams in the interaction tube 18, and scattered by succeeding charged particles, and scattered beams 16 having a wavelength shorter than laser beams are emitted to the rear. Scattered beams 16 are passed through the reflecting mirror 14 and an output mirror 21, and extracted to the outside. Charged particles used for scattering are reutilized for exciting the gas laser, thus facilitating miniaturization and improvement in efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scattered light generator for reusing charged particles for gas laser light scattering for gas laser excitation.

[0002]

2. Description of the Related Art When a laser beam is scattered by charged particles to obtain light having a shorter wavelength than the laser beam, conventionally, an excitation power source for generating a laser beam and a power source for generating and accelerating an electron beam for scattering are respectively provided. being independent.

The charged particles generated by the charged particle generator are accelerated by an accelerator, while the laser is oscillated synchronously. This laser may be a solid-state laser, a gas laser, or a semiconductor laser, and there are various excitation methods. Generally, a carbon dioxide gas laser or a YAG laser capable of high output is used. When the charged particle beam guided by the guide magnetic field is incident on the laser light emitted from the laser output mirror, scattered light having a short wavelength is obtained by their interaction. This scattering phenomenon itself is known as Compton scattering and Thomson scattering.

For example, when a CO ₂ laser with a wavelength of 9.6 μm is scattered by electrons accelerated at 700 kV,
m scattered light is obtained. An example is Physical Review Letter Vol. 52, p. 425 (1984) (Physi).
cal Review Letters, Vol. 5
2, p425 (1984)).

If an excimer laser that oscillates in the ultraviolet region is used, it is possible to obtain scattered light of a short wavelength, which is a soft X-ray from the vacuum ultraviolet region.

When the laser light is coherent, the power density is larger than the threshold value, the electron energy dispersion is small, and the divergence angle is small, the charged particle has a wave number represented by the sum of the wave numbers of the laser light and the scattered light. Since the laser light is density-modulated and scatters the laser light in a fixed phase relationship with the scattered light (stimulated Compton scattering), coherent scattered light is generated. This scattered light is exponentially amplified.

This phenomenon can also be explained as oscillation of a free electron laser in which the electromagnetic field of laser light is used as a wiggler magnetic field.

[0008]

However, conventionally, since the high voltage power source for generating the laser beam and the high voltage power source for accelerating the charged particle beam are independent, the entire apparatus becomes large and the construction cost becomes high. In addition, since the charged particles hardly lose their energy, the operating efficiency of the entire system becomes low.

The synchronization between the laser oscillation and the generation of the charged particle beam is performed by an external trigger, but it is technically difficult in a noisy environment, and malfunctions are likely to occur.

An object of the present invention is to solve the above problems of the prior art, to eliminate the need for a signal system for synchronization, to have a simple structure, to have a high operation efficiency, to be small in size, and to reduce the construction cost. Is to provide.

[0011]

SUMMARY OF THE INVENTION A scattered light generator according to the present invention comprises a charged particle generator, the charged particle accelerator, a gas laser tube facing the charged particle generator for generating a laser beam, and a guide for the charged particle. It is composed of a magnetic field generator. In the method of the present invention, charged particles accelerated by the charged particle accelerator are collided with the laser light to scatter the laser light, and at the same time, the charged particles after the collision are introduced into the gas laser tube to excite the gas laser. It is characterized by reuse.

When the laser light is condensed by an appropriate optical system such as a condenser lens or an external reflecting mirror and collides with the charged particles near the beam waist of the laser light, the laser light and the charged particles strongly interact with each other. It works, and scattered light is generated efficiently.

When an electron having a small energy dispersion is used as the charged particle, the mass is small, so that the density is easily modulated by the interaction with the laser light, and coherent scattered light is generated.

[0014]

In the present invention, the charged particles used for generating scattered light by the interaction with the laser light are reused for laser excitation.

The charged particles have hardly lost their energy after the generation of scattered light. Also, the charged particles used for interaction must be mass, whereas the electron beam for laser gas excitation has a low quality limit,
Recycling of the charged particles used to generate scattered light is quite possible.

In the present invention, the efficiency of use of the energy of charged particles is improved, and since a high voltage power source for laser excitation is not required, the operation efficiency of the entire system is high, the structure of the device is simple, and downsizing is possible. Is. Also, because it operates from a single power supply, a sync signal system like the conventional method is required.
The safety against malfunction also improves.

[0017]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of a light generator for scattering charged gas laser gas excited by a charged particle beam according to the present invention. Here, an electron beam will be described as an example among the charged particle beams.

The charged particle generating and accelerating device is composed of an electron gun, a high voltage power source 1 and a high piezoelectric transmission system 2. Cathode 3
When a high voltage generated by the high-voltage power supply 1 is applied to the electron gun composed of the anode 4 and the high-voltage power transmission system 2, electrons are generated and accelerated between the cathode 3 and the anode 4.
The electrons are guided by the magnetic field generated by the guide magnetic field generating coil 6, propagated in the vacuum interaction tube 18, and then traversed by the magnetic field generated by the bending magnetic field generating coil 6 and pass through the foil 11. Then laser tube 1
It is injected into 7. Examples of the cathode 3 that constitutes the electron gun include a field emission cathode, a plasma cathode,
A thermionic emission type cathode, a photoelectron emission type cathode or the like is used.

As the accelerating means, an electrostatic accelerator, an induction linac and an RF linac are suitable in terms of operating voltage. Although FIG. 1 shows an electrostatic accelerator, a larger accelerator such as a microtron can be used in addition to these. The optimum energy of charged particles is the mass of charged particles, the type and pressure of gas laser medium,
It depends on the direction in which charged particles are injected into the laser tube and the size of the gas laser tube.
It is about V. The current is limited by the type of cathode, the type of accelerator, etc. Taking the pulse power technique as an example, the peak voltage can be changed up to several MV and the peak current can be changed up to several kA.

The foil 11 is intended to partition a laser tube 17 filled with a laser gas medium and a vacuum interaction tube 18. The foil 11 is made of a metal film or the like so as to allow electrons to pass therethrough.

In the laser tube 17, the electrons continuously collide with the laser gas medium to excite the laser gas medium (electron beam excitation). Guide magnetic field generating coil 8
The magnetic field due to suppresses the scattering of electrons due to collision,
Be guided. In order to avoid the collision of the electrons with the reflecting mirror 12, there is a method of bending the orbits of the electrons with a bending magnetic field generating coil 9 or the like.

On the other hand, laser light is emitted from the laser gas medium excited by electron collision, and the light is amplified while being folded back between the resonators composed of the reflecting mirror 12 and the output mirror 13. Part of the laser light passes through the output mirror 13, is reflected by the reflecting mirror 14, and is incident on the orbit of the electron beam in the interaction tube 18 toward the electron gun. At this time, the laser light is scattered by the subsequent electrons, and scattered light 16 having a shorter wavelength than the laser light is emitted backward.
The reflecting mirror 14 is selected to have a wavelength dependency that has a high reflectance for laser light and a low reflectance for scattered light of a shorter wavelength than that. Most of the scattered light passes through the reflecting mirror 14 and the output mirror 21, and is taken out to the outside.

For example, an electron beam having a peak voltage of 500 kV and a peak current of 1 kA and a wavelength 248 oscillated by the electron beam
The stimulated scattered light generated by the collision of the KrF excimer laser of nm will be described. In the case of stimulated scattering, the wavelength λ _{S of} scattered light can be approximated by the following equation.

Λ _S = λ / (2γ ² ), where λ is the wavelength of the KrF excimer laser, 248n
m is the m, and γ is the energy V (kV) of the electron normalized by the static energy of the electron, and is represented by the following equation.

Γ = V / 511 + 1 When the acceleration voltage is 500 kV, γ becomes about 2, and the wavelength λ ^{S of} scattered light becomes about 30 nm. Further, if the voltage of the accelerator is changed, the wavelength of scattered light also changes. If the energy conversion efficiency from electron kinetic energy to scattered light is 0.1%, the peak output of scattered light will be about 500 kW.
The reflecting mirror 14 is a dielectric multilayer film coated,
Since the scattered light 16 has a reflectance of about 90% only for the light near the wavelength of 248 nm, the scattered light 16 passes through the reflecting mirror 14 and is taken out to the outside.

The efficiency of the entire system is improved by reusing the electron beam that hardly loses the energy for exciting the laser beam.

As a second embodiment, as shown in FIG. 2, a condenser lens 19 is installed in front of and behind the reflecting mirror 14 so that the laser light from the output mirror 13 is condensed in the interaction tube 18. ,
By increasing the laser power density at the position where it collides with the electron beam, the interaction between the charged particles and the laser beam becomes strong, and stimulated scattering is easily realized. As an optical system for condensing light, a reflection type optical system such as the facet reflecting mirror 20 shown in FIG. 3 may be used in addition to the condensing lens 19 described above.

When the electron beam is used in the charged particles, it becomes easy to guide the charged particles by the guide magnetic field generating coil and the bending magnetic field generating coil. In other words, since the electron has a small mass, the magnetic field for guiding can be small. Further, since the electron has a small mass, density modulation easily occurs, so that there is an advantage that stimulated scattering is easily realized.

[0030]

As described above, according to the present invention, there is provided a laser scattered light generator which does not require a signal system for synchronization, has a simple structure, has high operation efficiency, is small in size, and has a low construction cost. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is an enlarged view showing another embodiment of the reflecting mirror.

[Explanation of symbols]

 1 High-voltage power supply 2 High-voltage transmission system 3 Cathode 4 Anode 5 Charged particle beam 6 Guide magnetic field generating coil 7 Bending magnetic field generating coil 8 Guide magnetic field generating coil 9 Bending magnetic field generating coil 10 Laser light 11 Foil 12 Reflector 13 Output Mirror 14 Reflecting mirror 15 Reflected laser light 16 Scattered light 17 Laser tube 18 Interaction tube 19 Condensing lens 20 One-sided reflecting mirror 21 Output mirror

Claims (4)

[Claims] 1. A charged particle generating device, a charged particle accelerating device, a gas laser tube which is arranged to face the charged particle generating device and generates a laser beam, and a guide magnetic field generating device for the charged particles.
It has an interaction tube for colliding charged particles accelerated by the charged particle accelerator with the laser light to scatter the laser light to generate scattered light, and a device for introducing the charged particles after collision into the gas laser tube. An apparatus for generating scattered light of a gas laser beam excited by a charged particle beam, which is characterized in that: 2. A step of guiding accelerated charged particles by a magnetic field generated by a magnetic field generating means and introducing them into a gas laser tube to oscillate a laser, and causing the laser beam to collide with the following accelerated charged particles to produce a laser beam. A step of generating scattered light having a shorter wavelength, and after generating accelerated scattered particles by colliding the accelerated charged particles with the gas laser light, they are guided by the magnetic field generating means in the same manner as the charged particles and re-excited to excite the gas laser. A method for generating scattered light of a charged particle beam excited gas laser light, comprising the step of utilizing. 3. A condensing lens or a conical reflecting mirror is attached to condense the laser light in the interaction tube where charged particles collide with the laser light.
An apparatus for generating scattered light of a charged particle beam excited gas laser light as described in the above. 4. A scattered light generator for a charged particle beam excited gas laser light according to claim 1, wherein an electron gun is used as the charged particle generator.