JP2017157728A - Bidirectional free electron laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain laser radiation light (especially, laser radiation light of short wavelength in extreme ultraviolet region, for example) of high intensity with high energy efficiency, while contributing to improvement of area utilization efficiency.SOLUTION: On the opposite sides of an undulator 1 having a self amplification spontaneous radiation function, superconducting linacs 3A, 3B are placed, respectively. Two superconducting linacs 3A, 3B inject electron beams accelerated, respectively, to the undulator 1, from inverse directions (8A, 8B), and obtain laser radiation light from the opposite sides of then undulator 1 (7B, 7A). The superconducting linac 3B decelerates an electron beam, entering from the superconducting linac 3A and exiting from the undulator 1, for energy recovery, whereas the superconducting linac 3A decelerates an electron beam, entering from the superconducting linac 3B and exiting from the undulator 1, for energy recovery.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a bidirectional free electron laser device.

  The use of short-wavelength radiation from the extreme ultraviolet region to the X-ray region has attracted attention. Particularly in the field of semiconductor devices, the integration density of integrated circuits depends on the exposure technology, and in order to realize a line width of 10 nm (nanometer) or less, extreme ultraviolet light having a wavelength of 13.5 nm is essential. It is said. However, there has never been a realistic light source that can irradiate such short-wavelength extreme ultraviolet light with the intensity necessary for mass production exposure, and the possibility of high-repetition free electron laser devices is left to the public.

Japanese Patent No. 2726920 Japanese Patent Laid-Open No. 9-246684 Japanese Patent No. 4457207

Eisuke Minehara, “JAEA Superconducting Linac Drive Free Electron Laser Toward Realization of Ultrashort Pulse, High Efficiency, High Power, Tunable Laser”, Synchrotron Radiation, Japan Synchrotron Radiation Society, 2001, Vol. 14, No. 3 (2001), p.182-189

  Patent Documents 1, 2 and 3 disclose a free electron laser device (hereinafter sometimes referred to as FEL) having an optical resonator for laser light, but the optical resonator is configured at 13.5 nm. Since there is no high-efficiency reflecting mirror that can be used, it is difficult to use an FEL that uses an optical resonator as an extreme ultraviolet light source because sufficient intensity of radiated light cannot be obtained. In order to obtain the 1 kW (kilowatt) level light intensity required for mass production exposure in this short wavelength region, a self-amplified spontaneous emission (Self-Amplified Spontaneous Emission) type free electron laser device using a long undulator is used. For this purpose, for example, driving using a superconducting linac as in Patent Document 3 and Non-Patent Document 1 is desirable.

  On the other hand, in view of energy efficiency and the like, it is important to recover the energy of the used electron beam. However, in the method of reversing the electron beam in order to recover the energy as described in Patent Document 3 and Non-Patent Document 1, an inversion arc portion (loop electron path) for inversion is essential. This can be an increase factor of the device installation area and a decrease factor of the area use efficiency of the facility. In particular, for example, when the electron beam energy is high enough to generate 13.5 nm laser light, even if the laser light generating portion is configured as a self-amplifying spontaneous emission type, the inverted arc portion (loop electron) Since the radius of the (road) is considerably increased, the area utilization efficiency of the facility is considerably deteriorated. Needless to say, an increase in the installation area of the apparatus and a decrease in the area utilization efficiency of the facility are not desirable.

  For the sake of concrete explanation, the configuration of the conventional FEL has been explained by paying attention to extreme ultraviolet light having a wavelength of 13.5 nm. However, when trying to obtain laser light having a wavelength other than 13.5 nm. The same can be said for.

  Accordingly, the present invention provides a bidirectional free electron laser apparatus capable of emitting high-intensity laser radiation (especially, laser radiation having a short wavelength in the extreme ultraviolet region) with high energy efficiency while contributing to improvement in area utilization efficiency. The purpose is to provide.

  A bidirectional free electron laser device according to one aspect of the present invention is a bidirectional free electron laser device that obtains laser radiation in both directions using an undulator having a self-amplifying spontaneous emission function, on both sides of the undulator. Two superconducting linacs are arranged one by one, each of which receives an electron beam to the undulator, and acceleration and energy are applied to the electron beam incident from one end of the undulator and emitted from the other end. The deceleration for recovery is performed by the two superconducting linacs.

  A bi-directional free electron laser apparatus according to another aspect of the present invention includes an undulator having a self-amplifying and spontaneous emission function, and two undulators disposed between the undulator, each having acceleration and deceleration functions for an electron beam. A superconducting linac and two electron guns for supplying electron beams to the two superconducting linacs, and each electron gun has an electron beam path passing through one superconducting linac, the undulator, and the other superconducting linac. By configuring, two electron beam paths having opposite electron beam traveling directions are formed, and laser radiation is obtained from both sides of the undulator.

  ADVANTAGE OF THE INVENTION According to this invention, the bidirectional free electron laser apparatus which can radiate | emit high intensity | strength laser radiation light (especially laser radiation light of the short wavelength of an extreme ultraviolet region, etc.) with high energy efficiency, contributing to the improvement of area utilization efficiency, etc. Can be provided.

1 is a schematic configuration diagram of a bidirectional free electron laser apparatus according to an embodiment of the present invention. It is explanatory drawing (a) of the path | route of a 1st electron beam and explanatory drawing (b) of the path | route of a 2nd electron beam which concern on the bidirectional | two-way free electron laser apparatus of FIG. It is a side view of the undulator which concerns on 1st Example of this invention. It is the side view (a) of the two undulator parts which concern on 2nd Example of this invention, (b), and the arrangement | positioning relationship figure (c) of two undulator parts. It is a block diagram of the FEL system which concerns on 4th Example of this invention.

  Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In each of the drawings to be referred to, the same part is denoted by the same reference numeral, and redundant description regarding the same part is omitted in principle.

  In the present invention, a self-amplified spontaneous emission (Self-Amplified Spontaneous Emission) mechanism using free electrons as a medium is called an undulator, and an electron linear accelerator is abbreviated as a linac.

[Description of basic configuration]
FIG. 1 is a schematic configuration diagram of a bidirectional free electron laser apparatus (hereinafter referred to as a bidirectional FEL) 100 according to an embodiment of the present invention. FIG. 1 shows the outline of each component device when the component devices of the bidirectional FEL 100 are viewed from above.

  The bidirectional FEL 100 includes an undulator 1, deflecting magnets 2A and 2B, superconducting linacs 3A and 3B, sorting magnets 4A and 4B, electron guns 5A and 5B, beam dumps 6A and 6B, and optical beam lines 7A and 7B. And comprising. The deflection magnets 2A and 2B may have the same configuration. Superconducting linacs 3A and 3B may have the same configuration. The sorting magnets 4A and 4B may have the same configuration. The electron guns 5A and 5B may have the same configuration. The beam dumpers 6A and 6B may have the same configuration. The light beam lines 7A and 7B may have the same configuration.

FIG. 2A shows an electron beam path 8A that is a path of the first electron beam emitted from the electron gun 5A. The electron beam path 8A passes from the electron gun 5A to the beam dump 6B via the sorting magnet 4A, the superconducting linac 3A, the deflecting magnet 2A, the undulator 1, the deflecting magnet 2B, the superconducting linac 3B, and the sorting magnet 4B in this order. It is a passage.
FIG. 2B shows an electron beam path 8B that is a path of the second electron beam emitted from the electron gun 5B. The electron beam path 8B reaches the beam dump 6A from the electron gun 5B via the sorting magnet 4B, the superconducting linac 3B, the deflecting magnet 2B, the undulator 1, the deflecting magnet 2A, the superconducting linac 3A, and the sorting magnet 4A in this order. It is a passage.

  In the following, for the sake of concreteness and clarification of the description, the X axis, the Y axis, and the Z axis that are orthogonal to each other are defined in the real space where the bidirectional FEL 100 is installed. It is assumed that the X axis and the Y axis are parallel to the horizontal plane, and the Z axis is parallel to the vertical plane. The length direction of the undulator 1, that is, the traveling direction of the electron beam traveling in the undulator 1 is parallel to the X axis. Further, the origin of the X axis is set at the center of the undulator 1, the deflection magnet 2A, the superconducting linac 3A, the sorting magnet 4A, the electron gun 5A, the beam dump 6A and the light beam line 7A are installed on the negative side of the X axis, and It is assumed that the deflection magnet 2B, the superconducting linac 3B, the sorting magnet 4B, the electron gun 5B, the beam dump 6B, and the light beam line 7B are installed on the positive side of the X axis. Also, the direction from the center of the undulator 1 toward the positive side of the X axis is defined as right, and the direction from the center of the undulator 1 toward the negative side of the X axis is defined as left.

  Symbols 1 a and 1 b respectively represent one end and the other end in the length direction of the undulator 1. In the undulator 1, the direction from the end 1 a to the end 1 b is parallel to the X axis and coincides with the direction from the negative side to the positive side of the X axis. Symbols 3Aa and 3Ab represent one end and the other end of the superconducting linac 3A. Symbols 3Ba and 3Bb represent one end and the other end of the superconducting linac 3B. Similar to the undulator 1, in each of the superconducting linacs 3A and 3B, the length direction coincides with the traveling direction of the electron beam. In the superconducting linac 3A, the direction from the end 3Aa to the end 3Ab is inclined from the X axis, but has a component from the negative side of the X axis to the positive side. In the superconducting linac 3B, the direction from the end 3Ba to the end 3Bb is inclined from the X axis, but has a component from the positive side to the negative side of the X axis.

  As shown in FIGS. 1 and 2 (a) and 2 (b), in the bidirectional FEL 100, superconducting linacs 3A and 3B are arranged on both sides of the undulator 1 so as to sandwich the long and common undulator 1 and accelerated by them. The emitted electron beam is guided to the common undulator 1 from opposite directions by changing the trajectory by the deflecting magnets 2A and 2B, thereby generating laser radiation light (that is, laser light based on the radiation light) by the self-amplifying spontaneous emission mechanism. Is. Laser radiation based on the electron beam accelerated by the superconducting linac 3A is guided to the light beam line 7B, and laser radiation based on the electron beam accelerated by the superconducting linac 3B is guided to the light beam line 7A. The laser radiation generated in the bidirectional FEL 100 may be a short wavelength free electron laser light. The short wavelength here refers to, for example, a wavelength from a wavelength belonging to the extreme ultraviolet region to a wavelength belonging to the X-ray region, for example, a wavelength within a range from 1 nm to several tens of nm.

  The electron beams generated by the electron guns 5A and 5B are bent by the distribution magnets 4A and 4B and guided to the superconducting linacs 3A and 3B, and the electron beams accelerated by the superconducting linacs 3A and 3B are deflected by the deflecting magnet 2A. After the trajectory is bent again at 2B, it is thrown into the undulator 1 (that is, incident).

The electrons emitted from the undulator 1 based on the electron beam from the electron gun 5A are guided to the superconducting linac 3B through the deflecting magnet 2B, and are reverse to the electrons accelerated by the superconducting linac 3B in the superconducting linac 3B. , The track is bent again by the sorting magnet 4B and guided to the beam dump 6B.
The electrons emitted from the undulator 1 based on the electron beam from the electron gun 5B are guided to the superconducting linac 3A through the deflecting magnet 2A, and are reverse to the electrons accelerated by the superconducting linac 3A in the superconducting linac 3A. , The track is bent again by the sorting magnet 4A and guided to the beam dump 6A.

  The energy recovered when the electrons are decelerated can be used as energy for accelerating electrons traveling in the positive direction in each superconducting linac. Further, since the electron beam is sufficiently decelerated while traveling in each superconducting linac in the negative direction, the radiation problem in the beam dumpers 6A and 6B can be avoided. That is, the intensity of radiation that can be generated in each beam dump can be kept low, and the radiation shielding level can be kept low. In each of the superconducting linacs 3A and 3B, the direction in which electrons are accelerated is referred to as a positive direction, and the opposite direction is referred to as a negative direction. In superconducting linac 3A, the direction from end 3Aa to end 3Ab is the positive direction, and in superconducting linac 3B, the direction from end 3Ba to end 3Bb is the positive direction.

[Description of operating principle]
The bidirectional FEL 100 according to the present embodiment is basically a combination of two short-wavelength free electron laser devices that use a self-amplifying spontaneous emission mechanism as an undulator function and a common long undulator. is there. In addition, in order to obtain a large output, acceleration and deceleration of bidirectional electrons are performed in parallel using a pair of superconducting linacs having no heat loss and high repetition.

  In order to generate short wavelength free electron laser light, high energy electron acceleration is required. When 13.5 nm extreme ultraviolet rays necessary for high-definition exposure in the semiconductor field are generated with a practical intensity, it is necessary to accelerate electrons to about 280 MeV (megaelectron volts). As the superconducting linacs 3A and 3B used to realize such acceleration of electrons with minimum energy loss, for example, the total length excited at 1.3 GHz (gigahertz) so that acceleration is performed at a rate of 20 MeV per meter (meter). A rectilinear multi-cavity resonator of about 15 m may be used. This linear multi-cavity resonator is made of a superconducting material and operates in a state of being immersed in an ultra-low temperature liquid from a refrigerator, so that the loss due to electric resistance is substantially zero. The two superconducting linacs 3A and 3B used in the present invention each require two electron beam paths therein, but there is no special technical restriction in this respect, and the already known technology. (In each superconducting linac, the path for the electron beam traveling in the positive direction and the path for the electron beam traveling in the negative direction are separated from each other in a single rectilinear multi-cavity resonator. And secure it).

  Laser radiation is obtained by a self-amplifying spontaneous emission mechanism when accelerated electrons travel through the undulator 1 in synchrotron, but the wavelength of the radiation is basically proportional to the magnetic field period in the electron beam path in the undulator 1. . For example, when trying to obtain extreme ultraviolet rays of 13.5 nm as radiated light, the magnetic field period is about 20 mm (millimeters). The length of the undulator 1 is mainly dependent on the energy of the introduced electrons. When obtaining radiated light in the extreme ultraviolet region, the electron energy when entering the undulator 1 is about 280 MeV. For example, a length in the range of 10 to 20 m is sufficient for the undulator 1.

Here, in general, the wavelength λ _L of the radiated light in the FEL is accurately determined by the following formula (1) as described in Non-Patent Document 1, for example.
λ _L = λu / 2γ ² · (1 + K / 2) (1)
λu represents the magnetic field period in the electron beam path in the undulator, γ represents the electron energy of the electron beam incident on the undulator, and K represents a coefficient determined by the magnetic field strength and the magnetic field period in the undulator.

  Therefore, in order to obtain the extreme ultraviolet radiation having the intensity of 1 kW at the wavelength of 13.5 nm by the bidirectional FEL 100 according to the present embodiment, the electron energy of 280 MeV as exemplified above, and about 20 mm An undulator 1 having a magnetic field period and having a length of about 20 m is required, and the value of the coefficient K in that case is about 1.5.

  Further, the undulator 1 also requires a bi-directional path for the electron beam. In this regard, for example, it is possible to easily secure the two paths by slightly widening the magnetic pole interval forming the periodic magnetic field. it can. Therefore, the undulator 1 itself can also be assembled using a known technique, and no special device is required for the configuration itself.

  However, as will be described later, when the traveling space of the electron beam is tapered so that the self-amplification function by the interaction between the electrons and the emitted light in the undulator 1 is further increased, the bidirectional electron paths are separated from each other. There is a need to. Therefore, the undulator 1 that is commonly used for the first electron beam incident from the superconducting linac 3A and the second electron beam incident from the superconducting linac 3B has a common periodic magnetic field path space for the first and second electron beams. Such a single undulator is not necessarily meant to include a configuration in which the periodic magnetic field passage spaces for the first and second electron beams are separated, but the arrangement spaces thereof are made common.

  By the way, in general, in a high-power FEL, it is necessary to process a large amount of high-energy electrons after emitting laser light. As described above, in the conventional energy recovery type linac such as Patent Document 3, a single superconducting linac is provided by providing a looped electron reversal arc portion (corresponding to the component 5 in FIG. 1 in Patent Document 3). The used electron beams are accelerated and decelerated, and the used electron beam is decelerated by changing the phase, thereby taking measures against radiation associated with disposal. However, from the viewpoint of the device configuration that can be used in the actual industrial field, when trying to obtain the required intensity of laser light, electrons of correspondingly high energy are essential, so the inversion arc part is inevitably large, The installation area of the entire apparatus increases, and the area utilization efficiency of the facility decreases (the inside of the looped reversing arc portion becomes a useless space).

  In this regard, in the bidirectional FEL 100 according to the present embodiment, the used electron beam is decelerated using the reverse deceleration electric field of the superconducting linac on the opposite side, and the energy recovered during the deceleration is accelerated by the positive electron beam. By using it for energy efficiency. That is, in this embodiment, since the bidirectional FEL 100 is configured based on a new idea that two independent superconducting linacs 3A and 3B are used for acceleration and deceleration instead of the reversing arc portion, the entire apparatus The installation area can be reduced and the area utilization efficiency can be greatly improved. In addition, by decelerating the used electron beam as described above, it is possible to reduce radiation shielding measures against used high-energy electrons.

Incidentally, as described above, for example, if the length of the undulator 1 is set to 20 m and the length of the acceleration system centering on the superconducting linacs 3A and 3B is set to 15 m, the bidirectional FEL 100 has a total length of 50 m. × 10m square, that is, fits in a 500m ² factory building. This size is less than 1/5 in area ratio compared to conventional facilities that require an inverted arc portion (loop electron path) of the electron beam as disclosed in Patent Document 1 and Patent Document 3, It can be said that it is extremely realistic as equipment. In addition, since two radiation beam lines can be obtained simultaneously, the area utilization efficiency of the facility is further doubled. In other words, according to the bidirectional FEL 100 according to the present invention, in obtaining short-wavelength radiation with a desired intensity, the area utilization efficiency can be achieved 10 times as a whole as compared with the conventional FEL such as Patent Document 1, and the cost is remarkably high. It can be cheaper. The present invention is considered to contribute to high-definition exposure technology and to improve manufacturing efficiency, particularly in the field of semiconductor devices.

  The configuration and operation of the bidirectional FEL 100 described above are referred to as a basic configuration example for convenience. Hereinafter, in a plurality of embodiments, a more detailed configuration, application technology, modification technology, and the like of the bidirectional FEL 100 will be described. Unless otherwise stated and there is no contradiction, all the above-described matters described for the basic configuration examples apply to each embodiment described later, and in each embodiment, items that contradict the basic configuration example are described in each embodiment. Takes precedence. As long as there is no contradiction, the matters described in any of the plurality of embodiments described below can be applied to any other embodiment (that is, any two or more of the plurality of embodiments). It is also possible to combine these embodiments).

[First embodiment]
A first embodiment will be described. In the first embodiment, a detailed example of the configuration and operation of the bidirectional FEL 100 will be described. As is clear from the above-described matters, the bidirectional FEL 100 includes a left system (first acceleration system) composed of a device group disposed on the left side of the undulator 1 and a right system composed of a device group disposed on the right side of the undulator 1. The system (2nd acceleration system) and the undulator 1 which should also be called the common undulator shared by the left system and the right system are comprised.

The left electron gun 5A generates and emits a first electron beam. For example, the first electron stream generated by the electron gun 5A is launched from the electron gun 5A as a first electron beam intermittent at a repetition frequency of about 1 GHz (gigahertz). The first electron beam emitted from the electron gun 5A is given a predetermined initial velocity at a first stage acceleration (not shown) and then enters the sorting magnet 4A.
The sorting magnet 4A guides the first electron beam to the end 3Aa of the superconducting linac 3A by bending the trajectory of the first electron beam from the electron gun 5A, whereby the first electron beam enters the superconducting linac 3A (ie, incident). )
The superconducting linac 3A accelerates the first electron beam incident from the electron gun 5A via the sorting magnet 4A, and emits the accelerated first electron beam from the end 3Ab of the superconducting linac 3A. The first electron beam is accelerated until it has energy of about 280 MeV while traveling in the superconducting linac 3A.
The distribution magnet 2A guides the first electron beam to the end 1a of the undulator by bending the orbit of the first electron beam emitted from the other end 3Ab of the superconducting linac 3A, and is thereby accelerated by the superconducting linac 3A. The first electron beam is introduced (that is, incident) into the undulator 1 from the end 1a.

  The first electron beam injected into the undulator 1 travels in the right direction (that is, the positive direction of the X axis) while being contributed to synchrotron radiation by the periodic magnetic field formed by the undulator 1, and is emitted from the end 1b. Synchrotron radiation based on the first electron beam is emitted to the light beam line 7B as the first laser light (in other words, the first laser radiation), and is used as it is or through a necessary optical amplifier (not shown). Is done.

  The first electron beam emitted from the end 1b of the undulator 1 is guided to the end 3Bb of the superconducting linac 3B after the trajectory is bent by the deflecting magnet 2B. As a result, the first electron beam after traveling in the undulator 1 is input (that is, incident) into the superconducting linac 3B and travels in the superconducting linac 3B from the end 3Bb toward the end 3Ba. Via, it is thrown away into the beam dump 6B.

  In the superconducting linac 3B, there is an electric field for accelerating the second electron beam traveling in the positive direction (that is, the direction from the end 3Ba toward the end 3Bb), and the electric field travels in the negative direction. Since the reverse action is exerted on the electron beam, the first electron beam is sufficiently decelerated while traveling in the superconducting linac 3B. The superconducting linac 3B collects energy for the deceleration of the first electron beam, and reuses the collected energy as energy for accelerating the second electric beam traveling in the positive direction. A known method can be used as a method for recovering and reusing such energy.

The right-system electron gun 5B generates and emits a second electron beam. For example, the second electron stream generated by the electron gun 5B is launched from the electron gun 5B as a second electron beam that is intermittent at a repetition frequency of about 1 GHz (gigahertz). The second electron beam emitted from the electron gun 5B is given a predetermined initial velocity at a first stage acceleration (not shown) and then enters the sorting magnet 4B.
The sorting magnet 4B bends the trajectory of the second electron beam from the electron gun 5B to guide the second electron beam to the end portion 3Ba of the superconducting linac 3B, whereby the second electron beam is input to the superconducting linac 3B (ie, incident). )
The superconducting linac 3B accelerates the second electron beam incident from the electron gun 5B via the sorting magnet 4B, and emits the accelerated second electron beam from the end 3Bb of the superconducting linac 3B. The second electron beam is accelerated until it has energy of about 280 MeV while traveling in the superconducting linac 3B.
The sorting magnet 2B guides the second electron beam to the end 1b of the undulator by bending the trajectory of the second electron beam emitted from the other end 3Bb of the superconducting linac 3B, and is thereby accelerated by the superconducting linac 3B. The second electron beam is introduced (that is, incident) into the undulator 1 from the end 1b.

  The second electron beam injected into the undulator 1 travels in the left direction (that is, the negative direction of the X axis) while being contributed to synchrotron radiation by the periodic magnetic field formed by the undulator 1, and is emitted from the end 1a. The synchrotron radiation based on the second electron beam is emitted to the optical beam line 7A as the second laser light (in other words, the second laser radiation) and used as it is or through a necessary optical amplifier (not shown). Is done.

  The second electron beam emitted from the end 1a of the undulator 1 is guided to the end 3Ab of the superconducting linac 3A after the trajectory is bent by the deflecting magnet 2A. As a result, the second electron beam after traveling in the undulator 1 is input (that is, incident) into the superconducting linac 3A and travels in the superconducting linac 3A from the end 3Ab toward the end 3Aa. Via, it is thrown away into the beam dump 6A.

  In the superconducting linac 3A, there is an electric field for accelerating the first electron beam traveling in the positive direction (that is, the direction from the end 3Aa toward the end 3Ab), and the electric field is the second traveling in the negative direction. Since the opposite effect is exerted on the electron beam, the second electron beam is sufficiently decelerated while traveling in the superconducting linac 3A. The superconducting linac 3A collects the energy of the deceleration of the second electron beam and reuses the collected energy as energy for accelerating the first electric beam traveling in the positive direction. A known method can be used as a method for recovering and reusing such energy.

  Each laser beam derived to the optical beam lines 7B and 7A includes harmonics. When the bidirectional FEL 100 is configured with the numerical examples shown in the description of the basic configuration example, the fifth harmonics thereof are included. The wave will have a wavelength of 13.5 nm. Therefore, when performing high-definition exposure using 13.5 nm laser light, the fifth harmonic of each laser light derived to the light beam lines 7B and 7A is selected and used.

  As described above, the undulator 1 has a self-amplifying spontaneous emission function. In other words, the self-radiation function that generates radiant light based on the electron beam incident on itself without applying external power, and the intensity of the generated radiant light without using an optical resonator. Self-amplifying function. That is, when considering the first electron beam, the undulator 1 generates light by the synchrotron radiation based on the periodic magnetic field in the undulator 1 and the first electron beam (spontaneous emission), and uses the generated light. Then, density modulation is performed on the electrons constituting the first electron beam at the wavelength interval of the light, and the light intensity is amplified by aligning the phases of the light emitted from many electrons (self-amplification). The same applies to the second electron beam.

  Thus, the superconducting linac 3A has an acceleration function for accelerating the first electron beam and a decelerating function for decelerating the second electron beam, while the superconducting linac 3B has an acceleration function for accelerating the second electron beam. The decelerating function for decelerating the first electron beam is provided, and the energy for decelerating is recovered in the superconducting linacs 3A and 3B. That is, two superconducting linacs 3A perform acceleration and deceleration for energy recovery on an electron beam incident from one end (1a or 1b) of the undulator 1 and emitted from the other end (1b or 1a). And 3B.

  FIG. 3 shows a side view of an undulator 10 that can be used as the undulator 1. The undulator 10 includes magnet rows M1 and M2 arranged in parallel with a gap so as to face each other. FIG. 3 is a side view of the magnet arrays M1 and M2 constituting the undulator 10 when viewed along a direction parallel to the Y axis. In FIG. 3, the magnet row M1 is arranged on the upper side with respect to the magnet row M2. Each of the magnet row M1 and the magnet row M2 is formed by a plurality of magnets MG arranged in a straight line. Each magnet MG is formed of a permanent magnet such as a neodymium magnet. In FIG. 3, the arrows marked in each magnet MG indicate the magnetization direction of each magnet MG (the direction from the S pole to the N pole) (the same applies to FIGS. 4A and 4B described later). ).

  The magnetization direction of the plurality of magnets MG included in the magnet array M1 and the magnetization direction of the plurality of magnets MG included in the magnet array M2 periodically change along the X-axis direction, and based on the periodic change, the magnet array A periodic magnetic field B is formed between M1 and M2. In the periodic magnetic field B, the direction and magnitude of the magnetic field component perpendicular to the X axis change periodically, and the period corresponds to the above-described magnetic field period λu.

  The interval between the magnet arrays M1 and M2 is referred to as the magnetic pole interval. If this magnetic pole interval is set appropriately, two paths PS1 and PS2 separated from each other can be secured in the space between the magnet arrays M1 and M2. The path PS1 is a path of the first electron beam in the undulator 10 that is a part of the electron beam path 8A shown in FIG. The path PS2 is a path of the second electron beam in the undulator 10 that is a part of the electron beam path 8B shown in FIG. In FIG. 3, the passages PS1 and PS2 are separated along the Z-axis direction. However, as long as the passages PS1 and PS2 are separated from each other, their positional relationship is arbitrary. For example, the passages PS1 and PS2 May be separated along the Y-axis direction.

  In FIG. 3, since the magnet array M1 is arranged on the upper side with respect to the magnet array M2, in the periodic magnetic field B, the direction and magnitude of the Z-axis component of the magnetic field periodically change. In the periodic magnetic field B, the positional relationship between the magnet array M1 and the magnet array M2 is arbitrary as long as the direction and magnitude of the magnetic field component perpendicular to the X axis changes periodically. For example, the magnetic pole spacing between the magnet arrays M1 and M2 The magnet arrays M1 and M2 may be arranged side by side so that the direction of is parallel to the Y axis.

  In FIG. 3, Halbach type magnet arrays in which four magnets MG are arranged in one cycle are illustrated as the magnet arrays M1 and M2, but any type of magnet array that can constitute the periodic magnetic field B is illustrated. It may be used as the magnet arrays M1 and M2 (the same applies to the second embodiment described later).

[Second Embodiment]
A second embodiment will be described. 4A and 4B are side views of the undulator portions 20A and 20B according to the second embodiment. It can be used as the undulator 20 (see FIG. 4C) including the undulator portions 20 </ b> A and 20 </ b> B.

  Each of the undulator portions 20A and 20B includes magnet arrays M1 and M2 arranged so as to be opposed to each other, and has a self-amplifying spontaneous emission function, like the undulator 10 of FIG. FIG. 4A shows a side view of the magnet arrays M1 and M2 constituting the undulator unit 20A when viewed along a direction parallel to the Y axis. FIG. 4B shows a side view of the magnet arrays M1 and M2 constituting the undulator unit 20B when viewed along a direction parallel to the Y axis. As shown in FIG. 4C, the undulator portions 20A and 20B are arranged side by side in the Y-axis direction.

  In each of the undulator portions 20A and 20B, the configuration of the magnet arrays M1 and M2 is the same as that described in the first embodiment. Therefore, in each of the undulator portions 20A and 20B, the magnetization directions of the plurality of magnets MG included in the magnet array M1 and the magnetization directions of the plurality of magnets MG included in the magnet array M2 change periodically along the X-axis direction. Based on the periodic change, a periodic magnetic field is formed between the magnet arrays M1 and M2. In each periodic magnetic field, the direction and magnitude of the magnetic field component perpendicular to the X axis change periodically, and the period corresponds to the above-described magnetic field period λu.

  In the undulator unit 20A, the space between the magnet rows M1 and M2 in which the periodic magnetic field of the undulator unit 20A is formed is referred to as a path space PSa, and in the undulator unit 20B, the space between the magnet rows M1 and M2. The space in which the periodic magnetic field of the undulator unit 20B is formed is called a path space PSb. As understood from the fact that the undulator portions 20A and 20B are arranged side by side in the lateral direction, the path spaces PSa and PSb are two spaces separated from each other.

  In the second embodiment, the path space PSa serves as a path for the first electron beam that travels in the positive direction of the X axis in the undulator portion 20A, and the path space PSb travels in the negative direction of the X axis in the undulator portion 20B. It becomes a path for two electron beams. That is, when the undulator 20 is used as the undulator 1, the path space PSa functions as an electron beam path in the undulator 1 that is a part of the electron beam path 8A shown in FIG. 2B functions as an electron beam path in the undulator 1, which is a part of the electron beam path 8B shown in FIG.

  The first electron beam travels in the right direction (that is, the positive direction of the X axis) in the path space PSa, and the second electron beam travels in the left direction (that is, in the negative direction of the X axis) in the path space PSb. However, the path space PSa has a taper that expands in the traveling direction of the first electron beam (that is, in the right direction), and the path space PSb extends in the traveling direction of the second electron beam. On the other hand, it has a taper that spreads out (ie, toward the left).

More specifically, in the undulator section 20A, the magnetic pole spacing between the magnet arrays M1 and M2 increases as it goes to the right, that is, the cross-sectional area of the path space PSa increases as it goes to the right. The magnet rows M1 and M2 of the undulator section 20A are arranged so as to be inclined with respect to the magnet rows M1 and M2 of the undulator 10. In the example of the undulator portion 20A in FIG. 4A, the magnet arrays M1 and M2 are arranged in a plane parallel to the Z axis and the X axis so that the magnetic pole spacing, which is the distance in the Z axis direction, increases toward the right. It is arranged at an angle.
Similarly, in the undulator unit 20B, the undulator 10 of FIG. 3 is configured such that the magnetic pole spacing between the magnet arrays M1 and M2 increases toward the left, that is, the cross-sectional area of the path space PSb increases toward the left. The magnet rows M1 and M2 of the undulator section 20B are arranged so as to be inclined with respect to the magnet rows M1 and M2. In the example of the undulator portion 20B of FIG. 4B, the magnet arrays M1 and M2 are arranged in a plane parallel to the Z axis and the X axis so that the magnetic pole interval, which is the interval in the Z axis direction, increases toward the left. It is arranged at an angle.
In the path spaces PSa and PSb, the cross-sectional area refers to an area in a cross section orthogonal to the X axis (that is, a cross section orthogonal to the traveling direction of the electron beam).

  By providing the taper as described above, a stronger interaction appears between the light generated by the synchrotron radiation generated by the meandering traveling of the first electron beam and the first electron beam in the undulator portion 20A, and self-amplification occurs. Increasing and stronger laser radiation is obtained. The same applies to the undulator unit 20B. The undulator unit 20A and the undulator unit 20B may have the same configuration except that the taper spreading direction is different.

  As described above, in the example shown in FIG. 4C, the undulator portions 20A and 20B are arranged side by side in the Y-axis direction. Therefore, for example, the Z-axis coordinate value of the traveling axis of the first electron beam and the second electron beam Both the Z-axis coordinate values of the traveling axes may be zero, but the Z-axis coordinate values may be slightly different from each other (that is, the traveling axes of the first and second electron beams are viewed from the side. Sometimes, the travel axes may be completely overlapped or may be slightly deviated from each other).

  In the example shown in FIGS. 4A and 4B, the magnet row M1 is disposed above the magnet row M2. For this reason, in the undulator units 20A and 20B, the direction and magnitude of the Z-axis component of the magnetic field periodically change. However, as long as the direction and magnitude of the magnetic field component perpendicular to the X-axis change periodically. The positional relationship between the magnet array M1 and the magnet array M2 is arbitrary. For example, the magnet arrays M1 and M2 may be arranged side by side so that the direction of the magnetic pole spacing of the magnet arrays M1 and M2 is parallel to the Y axis.

  Furthermore, as long as the first electron beam travels in the right direction in the undulator unit 20A and the second electron beam travels in the left direction in the undulator unit 20B, the positional relationship between the undulator units 20A and 20B is arbitrary, and the undulator 20 It is sufficient that the undulator portions 20A and 20B are arranged in parallel in two stages. For example, the undulator portions 20A and 20B may be arranged in two upper and lower stages.

  The undulator 20 is a device that separates the path spaces of the periodic magnetic fields for the first and second electron beams, but shares the arrangement space of the entire undulator device including those path spaces. For example, the undulator unit 20A and 20B may be supported and integrated by a common mount (not shown).

[Third embodiment]
A third embodiment will be described. In the bidirectional FEL 100 shown in FIG. 1, a left system (first acceleration system) composed of a device group disposed on the left side of the undulator 1 and a right system (second acceleration system) composed of a device group disposed on the right side of the undulator 1. Are arranged in a mirror-symmetrical relationship with respect to the center of the undulator 1. That is, the arrangement positions of the deflection magnet 2A, the superconducting linac 3A, the distribution magnet 4A, the electron gun 5A, and the beam dump 6A are the arrangement positions of the deflection magnet 2B, the superconducting linac 3B, the distribution magnet 4B, the electron gun 5B, and the beam dump 6B, respectively. And symmetric with respect to an axis passing through the center of the undulator 1 and parallel to the Y axis.

  However, the left system and the right system described above may be arranged in a rotationally symmetric relationship with respect to the center of the undulator 1. That is, the arrangement positions of the deflection magnet 2A, the superconducting linac 3A, the distribution magnet 4A, the electron gun 5A, and the beam dump 6A are the arrangement positions of the deflection magnet 2B, the superconducting linac 3B, the distribution magnet 4B, the electron gun 5B, and the beam dump 6B, respectively. The arrangement relationship may be changed from that shown in FIG. 1 so as to have a point-symmetric relationship about the center of the undulator 1.

[Fourth embodiment]
A fourth embodiment will be described. As shown in FIG. 5, an FEL system including a plurality of bidirectional FELs 100 may be constructed. In the FEL system, a plurality of bidirectional FELs 100 are arranged side by side along the Y-axis direction. For this reason, in each of the bidirectional FELs 100 constituting the FEL system, the laser beam directed to the right is derived from the light beam line 7B, and the laser beam directed to the left is derived from the light beam line 7A. Therefore, for example, if three bidirectional FELs 100 are arranged, a total of six light beam lines can be obtained. The FEL system is suitable for mass production exposure.

[Other variations, etc.]
The embodiment of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims. The above embodiment is merely an example of the embodiment of the present invention, and the meaning of the term of the present invention or each constituent element is not limited to that described in the above embodiment.

  The specific numerical values shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values. That is, for example, in the above-described embodiment, it was mainly considered to obtain laser light having a wavelength of 13.5 nm from the bidirectional FEL 100. However, by appropriately adjusting each parameter on the right side of the above formula (1), 13 Laser light having an arbitrary wavelength different from .5 nm may be obtained from the bidirectional FEL 100.

1 undulator 2A, 2B deflection magnet 3A, 3B superconducting linac 4A, 4B sorting magnet 5A, 5B electron gun 6A, 6B beam dump 7A, 7B light beam line 8A, 8B electron beam path 10, 20 undulator 100 bidirectional FEL (bidirectional) Free electron laser device)
PSa, PSb path space

Claims (5)

A bi-directional free electron laser device that obtains laser radiation in both directions using an undulator having a self-amplifying spontaneous emission function, one unit arranged on both sides of the undulator, and an electron beam incident on each undulator With two superconducting linacs
Bidirectionally characterized in that acceleration and deceleration for energy recovery are shared by the two superconducting linacs with respect to an electron beam incident from one end of the undulator and exiting from the other end. Free electron laser device. An undulator with a self-amplifying spontaneous emission function;
Two superconducting linacs arranged across the undulator and having acceleration and deceleration functions for the electron beam,
Two electron guns for supplying an electron beam to the two superconducting linacs,
By constructing an electron beam path from each electron gun through one superconducting linac, the undulator, and the other superconducting linac, two electron beam paths having opposite traveling directions of the electron beam are constructed and the undulator Bidirectional free electron laser device characterized by obtaining laser radiation from both sides. The two superconducting linacs each enter an accelerated electron beam from opposite directions to the undulator, thereby obtaining the laser radiation from both sides of the undulator,
The one superconducting linac that constitutes the two superconducting linacs performs deceleration for the energy recovery with respect to the electron beam that is incident from the other superconducting linac and emitted from the undulator. Or the bidirectional free electron laser apparatus of 2. The bidirectional device according to claim 3, wherein the undulator has two path spaces separated from each other for two electron beams incident on the two superconducting linacs and traveling in opposite directions. Free electron laser device. 5. The bidirectional free electron laser device according to claim 4, wherein each path space has a taper with respect to the traveling direction of the corresponding electron beam.

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