JPH01311600A - Synchrotron radiation light generator - Google Patents

Abstract

PURPOSE:To extend the life of a charged particle beam and stabilize the SOR light by capturing gas molecules, photoelectrons and ions generated by the radiation of the SOR light. CONSTITUTION:The DC voltage is applied using a beam duct 2 as a cathode and an absorber 5 as an anode. Gas molecules and photoelectrons are emitted by the action of the synchrotron radiation light (SOR light). Some of the photoelectrons are pulled and captured by the absorber 5 side along the electric field. The other photoelectrons collide with the gas molecules and ionize them. The ionized gas molecules are pulled to the duct 2 side serving as the cathode and captured by the wall face. The gas emitted by the radiation of the SOR light and the residual gas in the duct are removed, the degree of vacuum in the duct is improved, ions are captured by the duct wall. The life of the electron beam is thereby extended.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a synchrotron radiation light generating device (hereinafter abbreviated as an SOR device), and in particular to an SOR device suitable for extending the life of a charged particle beam. Regarding.

[Conventional technology]

Conventionally, in accelerators and SOR devices, the beam duct consists of an extremely elongated annular container, as discussed in High Energy Physics Research Institute Report, Nα8l-2 (1981), pages 57 to 61. The interior is maintained at ultra-high vacuum.

The entire structure is composed of a deflection section that bends a beam of charged particles and generates SOR light, and a straight section that connects these deflection sections and has a quadrupole electromagnet for beam control.
These are divided into many parts and distributed approximately evenly throughout the ring. In the deflection section, SOR light is generated in the tangential direction of the beam and irradiates the inner wall surface of the beam duct. A large amount of gas is generated from the wall surface irradiated with the SOR light due to optically stimulated desorption. Since the amount of gas generated is 10 to 100 times greater than the amount of gas released due to simple thermal desorption, this becomes a big problem when trying to maintain an ultra-high vacuum inside the beam duct. As mentioned above, in conventional devices, the deflection section is divided into many locations throughout the beam duct and is evenly arranged, so the gas source generated from the wall surface of the beam duct due to SOR light irradiation is also distributed almost along the beam trajectory. distributed all around. Therefore, vacuum evacuation has been performed by arranging a large number of relatively small vacuum pumps throughout the beam duct and further installing a built-in pump on the inner peripheral side of the duct in the deflection section. This small-capacity, large-uniform vacuum pumping system maintains an ultra-high vacuum inside the beam duct.
The lifespan of the charged particle beam could be maintained for a fairly long period of time.

[Problem that the invention seeks to solve]

However, even in conventional SOR devices, the lifetime of the charged particle beam cannot be said to be sufficiently long, and there has been a strong demand for improving this by further improving the degree of vacuum.

Furthermore, if you want to apply the SOR device to industrial use,
This issue becomes even more important. That is, industrial SOR devices need to be downsized due to installation space restrictions and reduction in manufacturing costs, and therefore a compact configuration is required in which the number of deflection parts is reduced as much as possible. For example, deflection unit 1
Racetrack type S that bends charged particles 180' at certain points
The OR device is composed of two deflecting sections and two straight sections. This is a large SO with 200 deflection parts.
Compared to the R device, for the same beam energy, the amount of gas generated by the SOR light per deflection section is about 10 times greater. Furthermore, since the size of the uneven thickness section itself must be made smaller rather than a large device, it is also difficult to increase the number of vacuum pumps. Therefore, if the vacuum system of a large SOR device is applied as is to a small SOR device,
There was a problem in that sufficient exhaust capacity could not be obtained, the pressure inside the beam duct would increase, and the life of the charged particle beam would be further shortened.

Also, when SOR light hits a wall, not only gas but also
Excite and emit photoelectrons. When these photoelectrons collide with other gas molecules within the duct, they ionize them. As the ionized gas molecules fly around inside the duct, they become neutral when they collide with the electrons in the charged particle beam, and the beam current is lost accordingly. This is so-called ion trapping development, which also shortens the lifetime of the charged particle beam.

The purpose of the present invention is to provide a synchrotron radiation light generation device that can prolong the life of a charged particle beam and supply stable SOR light by capturing gas molecules, photoelectrons, and ions generated by SOR light irradiation. It is about providing.

[Means for solving problems]

The above object is achieved by providing a beam absorber at a position exposed to the SOR light in the deflection section beam duct, insulating the beam absorber and the beam duct, and applying a DC voltage therebetween. Furthermore, a greater effect can be obtained by using, as the material of the beam absorber, a so-called low photostimulation desorption coefficient material, which has a small amount of gas desorbed when irradiated with SOR light.

[Effect]

Gas is emitted from the wall surface irradiated with the SOR light, and photoelectrons are excited and emitted. Although the mechanism by which gas is released by SOR light has not yet been fully elucidated,
At present, there are two types of gas emitted from the directly irradiated wall surface, the emitted gas generated when reflected light irradiates other walls in the beam duct, and the gas emitted from the wall surface due to the action of the emitted photoelectrons. It is said that it will happen. The photoelectrons generated within the deflection section do not fly around freely, but are influenced by the strong magnetic field of the electromagnetic pressure of the uneven thickness section, and move in a spiral along the direction of the magnetic field. To draw a spiral trajectory,
Photoelectrons travel extremely long distances within the duct. As it moves, it collides with residual gas molecules in the duct and ionizes them.

With the above configuration, ions generated within the duct are attracted to the low potential side and captured on the cathode side wall surface according to the electric field based on the application of a DC voltage. Photoelectrons are also captured on the anode side while tracing a spiral trajectory. In this way, part of the gas generated by SOR light irradiation is captured by the cathode, reducing the residual gas in the beam duct and improving the degree of vacuum, and the effect of preventing ion trapping due to the action of the electric field. This makes it possible to extend the lifetime of the charged particle beam.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a sectional view of the deflection section of the SOR device.

la and lb are uneven thickness electromagnets, and 2 is a beam duct, the inside of which is maintained at an ultra-high vacuum. The electron beam 3 running inside the duct is deflected by the action of the electromagnet 1, and at the same time the SO
R light 4 is emitted outward in the connecting direction of the electron beam track.

5 is an absorber that receives the SOR light 4 irradiation. From the irradiated surface, gas molecules 6 shown by ■ and photoelectrons 7 shown by ○ are emitted, and reflected light 8 shown by ■ hits the duct wall surface, and gas molecules 9 also shown by ■ are emitted. discharge. 10 is a cooling pipe for the absorber. 11 is a chamber for the built-in pump, 12 is the built-in pump, and 13 is a window connecting the beam duct and the built-in chamber. The built-in pump is usually an ion pump or a non-evaporative getter pump.

The absorber 5 is electrically insulated from the beam duct 2, and a lead wire 14 is connected to a current introduction terminal 15 from one end of the absorber 5.
It is led to the outside through.

Externally, a DC voltage is applied between the absorber 5 and the beam duct 2 by a DC power supply 16 . In this embodiment, the beam absorber side is set to a positive potential, the beam duct side is set to a negative potential, and the beam duct side is grounded.

In order to deepen understanding, the behavior of gas molecules and photoelectrons induced by SOR light irradiation will be explained in the second part. When SOR light 4 is generated within the beam duct 2 and irradiates the absorber 5, gas molecules 6a and photoelectrons 7a are emitted, and gas molecules 9 are also emitted by the reflected light 8. Gas molecules usually fly around inside the duct and are evacuated with a certain probability by a built-in pump or a vacuum pump installed connected to the straight duct outside the deflection section. The photoelectrons are also generated by the magnetic field 19 generated by the bending electromagnet.

Since they receive a force perpendicular to the direction of movement, they move while tracing spiral trajectories 20a and 20b.

When the photoelectrons 7a collide with the gas molecules 6b, they are ionized and ions 21 are generated. When photoelectrons move in a spiral motion, the distance they travel becomes longer, which increases the probability of collision with gas molecules. In conventional SOR devices, ionized gas molecules fly around in the duct like neutral gas molecules, and are eventually evacuated by a vacuum pump with a certain probability. Alternatively, some of them return to neutral gas molecules after colliding with other photoelectrons or secondary electrons generated during ion production. Furthermore, some of the objects that happen to enter the orbit of the electron beam 7 combine with the beam electrons and cause ion trapping.

Next, the operation and effects of this embodiment will be explained.

FIG. 3 is an enlarged view of the vicinity of the absorber in FIG. 1. In the figure, the beam duct 2 is grounded, and a DC power supply 16 applies a voltage to the absorber 5 on the high potential side.

By applying this DC voltage, an electric field is formed in the beam duct, with the absorber serving as an anode and the beam duct serving as a cathode. Consider a state in which gas molecules and photoelectrons are emitted from an absorber due to the action of SOR light as described above. Some of the photoelectrons are drawn along the electric field to the PLK pole side, that is, to the absorber side, while making a spiral motion under the influence of the magnetic field, as shown in 7b in the figure, and are finally captured by the absorber. While another photoelectron makes a spiral motion 7a,
It collides with the gas molecules 6a and ionizes them. The generated ions 21 are attracted to the cathode side, that is, the beam duct 2 side, by the action of the electric field and are captured on the wall surface. Also, among the secondary electrons generated during ionization, 1
Some are captured by the absorber 5, and others collide with gas molecules to generate ions again. In this way, it is captured in the beam duct. In other words, the gas emitted by the SOR light and its reflected light, or the gas originally present in the duct, is captured on the beam duct wall by the above-mentioned action, independent of the vacuum pump included in the entire device. Therefore, the degree of vacuum inside the duct is improved. Furthermore, since it utilizes the effect of trapping ions on the duct wall, it also has the effect of preventing ion wrapping against the electron beam. These effects make it possible to extend the life of the electron beam.

FIG. 4 shows another embodiment. In this embodiment, contrary to the case shown in FIG. 3, the grounded beam duct side is set to a positive potential, that is, the anode, and the absorber side is set to the negative potential, that is, the cathode.

Therefore, in this embodiment, ions are captured by the absorber, and photoelectrons and secondary electrons that have not collided with gas molecules or ions are captured by the beam duct. The effect of the trapping action on gas molecules or the effect of preventing ion trapping is the same as in the case of FIG. 3, and the lifetime of the electron beam can also be extended.

In yet another embodiment, as the material of the absorber 5 shown in FIG. 1, a low photodetachment coefficient material made of extremely pure oxygen-free copper or aluminum may be used. In this case, since the amount of gas released by SOR light irradiation is already reduced, it is more effective in improving the degree of vacuum.

〔Effect of the invention〕

According to the present invention, gas molecules and ions emitted by SOR light are captured by the wall surface or absorber, improving the degree of vacuum in the beam duct and preventing ion trapping, thereby extending the lifespan of charged particles. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the beam deflection section of the SOR device, FIG. 2 is an enlarged cross-sectional view of the beam duct near the absorber, and FIG. 3 is an enlarged cross-sectional view of the beam duct of this embodiment. FIG. 4 is an enlarged sectional view of a beam duct of another embodiment. 1... Bending electromagnet, 2... Beam duct, 3...
Electron beam, 4... SOR light, 5... Absorber,
6... Released gas molecules, 7... Photoelectrons, 8... Reflected light, 9... Released gas molecules due to reflected light, 11... Built-in pump chamber, 12... Built-in pump, 14 ... Lead wire, 15 ... Current introduction terminal, 16 ... DC power supply, 2
0...Spiral electron orbit, 21...Ion. Fig. 2 2/l Inp Fig. 3

Claims (1)

[Claims] 1. In a synchrotron radiation generator surrounded by deflection electromagnets and having a beam duct necessary for circulating charged particles, irradiating the synchrotron radiation in the beam duct of the beam deflection section. What is claimed is: 1. A synchrotron radiation light generating device, characterized in that a beam absorber is provided at a position where the beam absorber is located, the beam absorber and the beam duct are electrically insulated, and a voltage is applied between the beam absorber and the beam duct. 2. The synchrotron radiation light generating device according to claim 1, wherein a material with a low optical desorption coefficient is used for the absorber.