JPH04344499A - Device for generating low speed positron - Google Patents

Abstract

PURPOSE:To provide a device in which cooling of a target is not required and which can be easily shielded from neutron radiation by making high energy electromagnetic wave which is photons incident on the target. CONSTITUTION:Laser light generated by a laser generator 6 is incident from a port 7 via a half mirror 8 and bombarded with electrons being accumulated in an electron accelerating and accumulating device 5. Then high energy electromagnetic wave is generated by the inverse Compton scattering of the laser light and high energy electrons. The high energy electromagnetic wave is taken out of the port 7 and incident on a target 2 through the half mirror 8. Then the high energy electromagnetic wave incident on the target 2 generates high- speed positrons through pair creation. The high-speed positrons are incident on a moderator 3 and have their speed lowered and are then taken out as an energy-adjusted low-speed positron beam by a pullout electrode 4. The electromagnetic wave is thus incident on the target 2 whereby it is made possible to restrain generation of heat and neutron radiation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slow positron generator for generating slow positrons.

0002

[Prior Art] Figure 2 shows, for example, the 20Me
1 is a conceptual diagram of main parts showing a conventional low-speed positron generation device described in "Positron generation experiment using V-electron linac". In the figure, 1 is an electron linear accelerator, 2 is a target made of Ta (tantalum), etc., 3 is a moderator made of W (tungsten), etc., which slows down high-speed positrons,
4 is an extraction electrode for extracting slow positrons.

[0003] Such a slow positron generator is used to analyze the structure of the surface of a material by colliding a positron beam with a material to be measured. A continuous beam is required. Since positrons do not exist in nature, they are created using high-energy electron beams.

Next, the operation will be explained. First, an electron beam is accelerated to high energy by an electron linear accelerator 1 and is made incident on a target 2 . The electron beam then emits powerful electromagnetic waves due to bremsstrahlung. When the energy of the radiated electromagnetic wave is 1 MeV or more, it becomes an electron and a positron due to a phenomenon called pair production. The energy of positrons generated by this pair generation ranges from several eV to several tens of M
Since the energy is widely distributed up to eV, the energy is made incident on the moderator 3 to adjust this energy to a low energy. As a result, a low-speed positron beam with uniform energy of several eV was obtained, which was extracted by the extraction electrode 4 and used.

[0005]

[Problems to be Solved by the Invention] As described above, the conventional slow positron generator has a configuration in which an electron beam is incident on the target 2 to generate high-energy electromagnetic waves, and positrons are obtained by pair generation of the electromagnetic waves. Therefore, when the electron beam collided with target 2, most of the energy of the electron beam was converted into thermal energy. Therefore, if a large amount of slow positrons were to be obtained, a large amount of heat would be generated in the target 2, making it extremely difficult to cool the target 2.

In addition, since the electron beam, which is a particle, is collided with the target, a large amount of low-energy electromagnetic waves that do not contribute to the production of neutrons and positrons is also generated, so there is a problem of contamination of the equipment itself with radiation and damage to the outside. There was a problem in that it became difficult to shield the equipment in order to keep the amount of leaking radiation within an allowable range.

The present invention was made to solve the above-mentioned problems, and aims to provide a low-speed positron generating device that does not require cooling the target and can be easily shielded from radiation such as neutrons. purpose.

[0008]

[Means for Solving the Problems] A low-velocity positron generating device according to the present invention is constructed such that a high-energy electromagnetic wave generating section that makes high-energy electromagnetic waves in the form of photons enter a target is provided.

[0009]

[Operation] According to the slow positron generator of the present invention, since high-energy electromagnetic waves in the form of photons are incident on the target, the amount of heat and radiation such as neutrons generated can be suppressed.

0010

【Example】

Example 1. FIG. 1 is a conceptual diagram showing an embodiment of a slow positron generator according to the present invention. In the figure, numerals 2 to 4 are similar to the conventional device. Reference numeral 5 denotes an electron acceleration storage device, which accelerates an electron beam to the speed of light and stores the beam by circulating it in a ring inside the device. 6 is a laser generator that generates a laser such as a YAG laser; 7 is a port for inputting and extracting laser light; 8 is a half mirror; together with the electron accelerating storage device 5, the laser generator 6, and the port 7, a high-energy electromagnetic wave generating section 10; It consists of Further, the moderator 3 and the extraction electrode 4 constitute a slow positron generation section 11.

Next, the operation will be explained. First, a laser beam generated by the laser generator 6 is made to enter from the port 7 via the half mirror 8 and collide with the electrons being accumulated in the electron accelerating and accumulating device 5 . Then, high-energy electromagnetic waves (eg, γ-rays) are generated by inverse Compton scattering between the laser beam and high-energy electrons. This high-energy electromagnetic wave is taken out from port 7 and made to enter target 2 through half mirror 8. At this time, the high-energy electromagnetic waves incident on the target 2 generate high-speed positrons through pair generation, and these high-speed positrons are made incident on the moderator 3, slowed down, and converted into a low-speed positron beam with uniform energy by the extraction electrode 4. I'll have to take it out. By making the electromagnetic waves enter the target 2 in this manner, it is possible to suppress the generation of radiation such as heat and neutrons.

Example 2. In the above embodiment, the high-energy electromagnetic wave generating section 10 is configured to collide a high-energy electron beam with a laser beam such as a YAG laser and generate a high-energy electromagnetic wave by inverse Compton scattering. It may be configured such that a high-energy electron beam is incident on the electron beam, and high-energy electromagnetic waves may be generated by channeling.

[0013]

[Effects of the Invention] As described above, according to the present invention, since high-energy electromagnetic waves in the form of photons are made incident on the target, the amount of heat and radiation such as neutrons generated at the target can be suppressed. As a result, a cooling device for the target can be made unnecessary, and a shielding device for preventing radiation leakage can be simplified.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a slow positron generator that is an embodiment of the present invention.

FIG. 2 is a conceptual diagram of main parts of a conventional slow positron generator.

[Explanation of symbols]

2 Target 3 Moderator 4 Extraction electrode 5　Electron acceleration storage device 6 Laser generator 10 High energy electromagnetic wave generation section 11 Slow positron generation section

Claims (1)

[Claims] 1. A high-energy electromagnetic wave generating section, a target for generating high-speed positrons by making the high-energy electromagnetic waves generated by the high-energy electromagnetic wave generating section incident, and slowing down the high-speed positrons generated by the target, A slow positron generator comprising a slow positron generator that generates slow positrons.