JP2002280200A - Device and method for generating x-ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray generator capable of comparatively simply changing the wave length of an X-ray generated by reverse Compton scattering. SOLUTION: A microtron demarcates plural revolving electron orbits a part of which is mutually shared. An accelerating tube to increase and decrease the energy of an electron beam is disposed in the shared part of the orbit. An electron beam source forces the electron beam enter into the revolving electron orbit of the microtron. A laser beam source emits a laser beam so as to make it collide with an electron flying in the shared part of the orbit of the microtron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray generating apparatus and an X-ray generating method, and more particularly, to a method of generating high quality monochromatic and short pulse X-rays by causing an electron beam and a laser beam to collide with each other to cause inverse Compton scattering. The present invention relates to an apparatus and a method for causing the same.

[0002]

2. Description of the Related Art There is known a technique for generating an X-ray by causing a laser beam to collide with an electron beam to cause inverse Compton scattering. The wavelength of the generated X-rays depends on the energy of the electron beam, the wavelength of the laser beam, and the collision angle. The X-ray wavelength can be changed by changing these parameters.

[0003]

When the wavelength of a laser beam to be collided is converted, the power of the laser beam usually decreases. For this reason, the intensity of the generated X-rays decreases. Further, when the collision angle is changed, the intensity and pulse width of the generated X-rays are changed. Changing the energy of the electron beam is not easy as it requires adjustment of the electron beam generation system.

[0004] It is an object of the present invention to provide an X-ray generating apparatus and method which can relatively easily change the wavelength of X-rays generated by inverse Compton scattering.

[0005]

According to one aspect of the present invention, an accelerating tube for defining a plurality of orbiting electron orbits, some of which are mutually shared, and increasing or decreasing the energy of an electron beam in a shared portion of the orbits. , An electron beam source that causes an electron beam to be incident on the orbital electron trajectory of the microtron, and a laser light source that emits a laser beam so as to collide with electrons flying on a common portion of the orbit of the microtron. An X-ray generator having:

The energy of the electron beam can be set to a desired value by the accelerator tube. As the energy changes, the electron beam passes through the shared portion of the orbit. Therefore, the laser beam can easily collide with the electron beam.

According to another aspect of the present invention, a step of increasing or decreasing the energy of the electron beam while circulating the electron beam along a plurality of orbiting electron orbits partially shared by the plurality of orbiting electrons. A step of causing a laser beam to collide with an electron beam flying on a common portion of the orbit to generate X-rays.

By setting the energy of the electron beam to a desired value, X-rays of a desired wavelength can be generated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows X according to an embodiment of the present invention.
1 shows a schematic diagram of a line generator. This X-ray generator includes a microtron 1, an electron beam source 13, a laser light source 20, and a synchronizer 30.

First, the configuration of the microtron 1 will be described. By a pair of bending electromagnets 10,
A plurality of race-track orbital electron trajectories 2 having different radii of curvature are defined. Each electron trajectory 2 has a linear portion 2
a, 2b and two semicircular portions 2c. The straight portion 2a is shared by all electron orbitals. The position of the other straight portion 2b is determined by the radius of curvature of the semicircular portion 2c. The radius of curvature of the semicircular portion 2c is
It is determined by the energy of electrons incident between the magnetic poles of the bending electromagnet 10.

An electron beam accelerating tube 11 is arranged along a part of the shared portion 2a of the electron trajectory 2. Frequency 2 output from microwave generation source 32 in synchronizer 30
A 856 MHz microwave is introduced into the acceleration tube 11 via the waveguide. The accelerating tube 11 increases the energy of the incident electron beam by a high-frequency electric field generated by a microwave. When the electron energy increases, the electron orbit 2
Has a larger radius of curvature of the semicircular portion 2c. Therefore, each time an electron passes through the accelerating tube 11, the radius of curvature of the semicircular portion 2c of the trajectory drawn by the electron increases.

It is also possible to decelerate the electron beam (decrease the energy of the electron beam) by shifting the phase of the microwave introduced into the accelerating tube 11 by 180 °.

The traveling direction of the electron beam that has circulated the electron trajectory 2 a predetermined number of times is changed by an electromagnet 15 disposed on a linear portion 2 b corresponding to the outermost trajectory of the electron trajectory 2, and the electron beam leaves the electron trajectory 2. . The electron beam separated from the electron orbit 2 travels in the extraction tube 16 in the axial direction and is extracted to the outside. In the present embodiment, the electron beam extracted to the outside is not used, but can be used for purposes other than the generation of X-rays.

The electron beam source 13 includes a trigger signal generator 14
And emits a pulsed electron beam based on the trigger signal given by. The trigger signal generator 14 generates a trigger signal so that the phase of the microwave output from the microwave generation source 32 is synchronized with the phase of the electron beam.

As the electron beam source 13, for example, an RF electron gun with a photocathode disclosed in JP-A-11-45676 can be used. In this case, a pulse laser oscillator is used as the trigger signal generator 14. The trigger signal generator 14 causes a short pulse laser beam to be incident on the photocathode of the RF electron gun in synchronization with the microwave having a frequency of 2856 MHz output from the microwave generation source 32.

The pulsed electron beam emitted from the electron beam source 13 enters the accelerator tube 11 from the emission end of the accelerator tube 11 along the electron trajectory 2a. The electron beam accelerated by the accelerating tube 11 is turned back by the bending electromagnet 10 on the incident end side, and returns to the incident end of the accelerating tube 11 along the electron trajectory 2a. The electron beam returned to the entrance end of the acceleration tube 11 is accelerated again by the acceleration tube 11 and exits from the exit end. The electron beam emitted from the emission end returns to the incidence end of the acceleration tube 11 along a race-track type electron trajectory 2. By repeating this orbital motion, the electron beam is gradually accelerated, and the electron trajectory 2 gradually increases.

When the electron beam emitted from the electron beam source 13 is made incident from the incident end of the accelerator tube 11, the radius of curvature of the semicircular portion of the first race-track orbital electron orbit becomes too small to return. The incident electron beam collides with the outer wall of the acceleration tube 11. In order to avoid this, the first electron beam is made incident from the emission end of the acceleration tube 11, the accelerated electron beam is turned back on the same linear trajectory, and re-entered into the acceleration tube 11 from the incidence end of the acceleration tube 11. I have. The electron beam incident from the entrance end is already
Since it is accelerated once at 1, a somewhat large radius of curvature can be secured in the semicircular orbital portion 2c. For this reason,
Even when the orbit is made along the race track type electron orbit 2, it does not collide with the outer wall of the acceleration tube 11.

The laser light source 20 includes a microwave source 32
A pulsed laser beam is emitted in synchronization with the microwave having a frequency of 2856 MHz output from. Laser light source 2
As 0, for example, a Ti sapphire laser oscillator can be used. The pulse laser beam emitted from the laser light source 20 enters the vacuum vessel through a window 17 provided in the vacuum vessel containing the electron orbit 2, and intersects the electron orbit 2.

When the pulsed laser beam collides with the electron beam orbiting along the electron trajectory 2, X-rays 18 are generated. The X-rays 18 propagate in the traveling direction of the electron beam, and are taken out of the microtron 1 through a duct 18 connected to the vacuum vessel 18.

The pulsed electron beam emitted from the electron beam source 13, the pulsed laser beam emitted from the laser light source 20, and the microwave applied to the accelerating tube 11 all have a frequency of 2856 MHz output from the microwave generation source 32.
It is synchronized with the microwave of z. Therefore, the probability that the pulsed laser beam collides with the electron beam orbiting the electron orbit can be increased.

In order to further increase the probability of collision, the following method may be employed. A current detector 33 is arranged in a part of the common portion 2a of all the orbits 2. The current detector 33 detects a current caused by electrons flying along the electron trajectory 2. The detection result is input to the laser light source control device 31 in the synchronization device 30.

The laser light source control device 31 includes the current detector 3
The trigger signal is sent to the laser light source 20 in synchronization with the current detected in step 3. The laser light source 20 emits a pulse laser beam in synchronization with the trigger signal. In this method, electrons orbiting the electron orbit 2 are directly monitored, so that the probability of collision between the pulsed electron beam and the pulsed laser beam can be further increased.

While circulating the electron beam along the electron orbit 2, the energy of the electron beam is increased or decreased to obtain an electron beam having a desired energy. When the energy of the electron beam reaches the desired energy, the pulsed laser beam collides with the electron beam to generate X-rays of a desired wavelength. Even if the energy increases or decreases, the electron beam always passes through the common portion 2a of the orbit.
Therefore, the pulse laser beam can easily collide with the electron beams of various energies.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0025]

As described above, according to the present invention,
A laser beam collides with an electron beam passing through a portion shared by a plurality of orbits of a microtron. The energy of the electron beam can be increased or decreased while orbiting the orbit. Therefore, the laser beam can collide with electron beams of various energies. Thereby, X-rays of a desired wavelength can be generated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an X-ray generator according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microtron 2 Electron orbit 10 Bending electromagnet 11 Acceleration tube 13 Electron beam source 14 Trigger signal generator 15 Electromagnet 16 Extraction tube 17 Window 18 Duct 20 Laser light source 21 Pulse laser beam 30 Synchronizing device 31 Laser light source control device 32 Microwave generation Source 33 current detector

Claims (5)

[Claims] 1. A microtron in which a plurality of orbiting electron orbits, some of which are shared with each other, are defined, and an accelerating tube for increasing or decreasing the energy of an electron beam is arranged in a shared portion of the orbits. An X-ray generator comprising: an electron beam source that causes an electron beam to enter a circulating electron orbit; and a laser light source that emits a laser beam so as to collide with electrons flying in a common portion of the orbit of the microtron. 2. A synchronizing means for synchronizing the electron beam source and the laser light source, wherein the laser light source emits a pulsed laser beam, the electron beam source causes a pulsed electron beam to be incident on the microtron. The X-ray generator according to claim 1, comprising: 3. The synchronizing means includes a microwave generator for generating a high-frequency electric field in the accelerating tube, wherein the electron beam source and the laser light source each output a microwave output from the microwave generator. 3. The X-ray generator according to claim 2, wherein a pulsed electron beam and a pulsed laser beam are emitted in synchronization with the X-ray. 4. A current detector for detecting a current caused by electrons flying on a common portion of the orbit of the microtron, and a synchronizing means for transmitting an oscillation trigger signal to the laser light source in synchronization with the detected current. 3. A control system according to claim 2, further comprising control means.
2. The X-ray generator according to claim 1. 5. A step of increasing or decreasing the energy of the electron beam while orbiting the electron beam along a plurality of orbital electron orbits partially shared, and flying in a shared portion of the plurality of orbital electron orbitals. Colliding a laser beam with an electron beam to generate X-rays.