JP2685503B2 - Synchrotron radiation generator - Google Patents

Description

The present invention relates to a synchrotron radiation light generator (hereinafter referred to as SOR device), and particularly to a SOR device suitable for prolonging the life of a charged particle beam. Regarding

[Conventional technology]

Conventionally, for accelerators and SOR devices, High Energy Physics Laboratory Report, No. 81-2 (1981), pages 57 to 61.
As discussed in the page, the beam duct consists of a very elongated annular vessel, the interior of which is maintained at ultrahigh vacuum. Also, the whole bends the beam of charged particles SOR
It is composed of a deflecting section for generating light and a linear section connecting the deflecting sections and having a quadrupole electromagnet for beam control, etc. These are divided into a large number and arranged substantially uniformly over the entire 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. S
A large amount of gas is generated by photostimulation desorption from the wall surface irradiated with OR light. The amount of gas generated is 10 to 100 times larger than the amount of gas released by mere thermal desorption, which is a big problem when trying to maintain an ultrahigh vacuum in the beam duct. As described above, in the conventional device, since the deflector is divided into a number of places throughout the beam duct and is evenly arranged, the gas source generated from the wall surface of the beam duct due to the SOR light irradiation also follows the beam trajectory. It is distributed all around. Therefore, by arranging a large number of relatively small vacuum pumps in the entire beam duct, and further by installing the built-in pump on the inner peripheral side of the duct of the deflection unit,
I have been evacuating. With such a small-capacity, large-biased vacuum evacuation system, the inside of the beam duct can be kept in an ultra-high vacuum, and the life of the charged particle beam can be maintained for a certain long time.

[Problems to be solved by the invention]

However, even in the conventional SOR device, the life of the charged particle beam cannot be said to be sufficiently long, and it has been strongly demanded to improve it by further improving the degree of vacuum.

If you want to further apply the SOR device for industrial use,
This problem becomes even more important. In other words, the industrial SOR device needs to be downsized due to restrictions on installation space and reduction in manufacturing cost, and therefore a compact configuration in which the number of deflecting parts is reduced as much as possible is required. For example, in a race track type SOR device that bends charged particles by 180 ° at one deflection portion, it is composed of two deflection portions and two straight portions.
Comparing this with a large-scale SOR device having 20 deflection sections, the amount of gas generated by SOR light per deflection section is about 10 times that of the same beam energy.
Moreover, since the size of the deflection unit itself must be smaller than that of a large-sized device, it is difficult to increase the number of vacuum pumps. Therefore, if the vacuum system of the large SOR device is directly applied to the small SOR device, sufficient exhaust capacity cannot be obtained, the pressure in the beam duct rises, and the life of the charged particle beam becomes even shorter. Atsuta

Also, when the SOR light collides with the wall, not only the gas,
Photoelectrons are excited and emitted. When the photoelectrons collide with other gas molecules in the duct, they ionize them. While the ionized gas molecules fly around in the duct, they collide with the electrons in the charged particle beam and are neutralized, so that the beam current is lost. This is so-called ion trapping development, which also shortens the life of the charged particle beam.

The purpose of the present invention is to extend the life of a charged particle beam by trapping gas molecules, photoelectrons and ions generated by irradiation of SOR light, and to provide stable SOR light and synchrotron radiation. It is to provide a light generation device.

[Means for solving the problem]

The above-mentioned object is achieved by providing a beam absorber at a position where it is irradiated with SOR light in the beam duct of the deflecting unit, insulating the beam absorber from the beam duct, and applying a DC voltage between them. It Furthermore, a greater effect can be obtained by using a so-called low photostimulation desorption coefficient material, which has a small amount of gas desorbed when irradiated with SOR light, as the material of the beam absorber.

[Action]

Gas is emitted from the wall surface irradiated with SOR light, and photoelectrons are excited and emitted. The mechanism by which the gas is released by SOR light has not been fully clarified yet, but at present, the emitted gas from the directly irradiated wall, reflected light irradiates the other wall in the beam duct. It is said that the photoelectrons generated in the deflection part, which are said to consist of the emission gas generated as a result, and the gas emitted from the wall surface by the action of the emitted photoelectrons, do not fly freely, but instead of a strong magnetic field of the deflection part electromagnetic pressure. It is affected and makes a spiral movement along the direction of the magnetic field. Because it draws a spiral trajectory, photoelectrons will travel a very long distance in the duct.
Then, when they collide with the molecules of the residual gas in the duct while moving, they are ionized.

With the above configuration, the ions generated in the duct are attracted to the low potential side and trapped on the side wall surface of the cathode according to the electric field based on the application of the DC voltage. Photoelectrons are also captured on the anode side while drawing a spiral locus. In this way, part of the gas generated by SOR light irradiation is captured by the cathode, the residual gas in the beam duct is reduced and the degree of vacuum is improved, and the ion trapping is performed by the action of the electric field. Since the effect of preventing the occurrence of the charged particle beam also occurs, the life of the charged particle beam can be extended.

〔Example〕

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

FIG. 1 is a cross-sectional view of the deflection section of the SOR device. Reference numerals 1a and 1b are electromagnets for the deflecting section, and 2 is a beam duct, and the inside thereof is kept in an ultrahigh vacuum. The electron beam 3 running in the duct is deflected by the action of the electromagnet 1, and at the same time, the SOR light 4 is emitted outward in the tangential direction of the electron beam guide. Reference numeral 5 is an absorber, which receives irradiation of SOR light 4. From the illuminated surface,
The gas molecules 6 indicated by and the photoelectrons 7 indicated by
Further, the reflected light 8 shown by hits the wall surface of the duct, and the gas molecules 9 also shown by are emitted. 10 is a cooling pipe of the absorber. 11 is a chamber for built-in pump, 12
Is a built-in pump, and 13 is a window connecting between the beam duct and the built-in chamber. As the built-in pump, an ion pump or a non-evaporable getter pump is usually used.

The absorber 5 is electrically insulated from the beam duct 2, and a lead wire 14 is led from the one end to the outside through a current introduction terminal 15. 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 has a positive potential and the beam duct side has a negative potential, and the beam duct side is grounded.

In order to deepen the understanding, the behavior of gas molecules and photoelectrons induced by SOR light irradiation will be explained in FIG. When the SOR light 4 is generated in the beam duct 2 and the absorber 5 is irradiated, gas molecules 6a and photoelectrons 7a are emitted, and reflected light 8
Also by this, the gas molecules 9 are released. Gas molecules are usually
While flying around the duct, there is a certain probability that the built-in pump,
The air is exhausted by a vacuum pump connected to a straight duct outside the deflecting unit. Further, the photoelectrons receive a force in a direction perpendicular to the moving direction due to the magnetic field 19 generated by the deflecting electromagnet 1, and therefore move while drawing spiral orbits 20a and 20b. When it collides with the photoelectrons 7a and the gas molecules 6b, these are ionized and ions 21 are generated. When the photoelectrons make a spiral motion, the moving distance increases, and thus the probability of collision with gas molecules increases. Ionized gas molecules fly around in a duct in the same manner as neutral gas molecules in a conventional SOR device, and are eventually exhausted by a vacuum pump with a certain probability. Alternatively, there are those that return to neutral gas molecules that collide with other photoelectrons or secondary electrons generated when ions are generated. Further, among those accidentally entering the trajectory of the electron beam 7, there are some that are coupled with the beam electrons and cause ion trapping.

Next, the operation and effect of this embodiment will be described. Third
The figure is an enlarged view of the vicinity of the absorber in FIG. In the figure, the beam duct 2 is grounded, and a voltage is applied to the absorber 5 on the high potential side by a DC power supply 16. By applying this DC voltage, an electric field is formed in the beam duct with the absorber as the anode and the beam duct as the cathode. Consider a state in which gas molecules and photoelectrons are emitted from the absorber by the action of SOR light as described above. Some of the photoelectrons are spiraled under the influence of a magnetic field as shown by 7b in the figure, and are attracted to the anode side, that is, the absorber side along the electric field, and finally captured by the absorber.
Another photoelectron collides with the gas molecule 6a during the spiral motion 7a and ionizes it. The generated ions 21 are attracted to the cathode side, that is, the side of the beam duct 2 by the action of the electric field, and are trapped on the wall surface. Further, of the secondary electrons generated during ionization, one part is captured by the absorber 5, and the other one collides with gas molecules to generate ions again. In this way, it is captured by the beam duct. That is, the gas emitted by the SOR light and its reflected light, or the gas originally existing in the duct is trapped on the beam duct wall by the above-mentioned action, in addition to the vacuum pump of the entire device. Therefore, the degree of vacuum in the duct is improved. Further, since the action of trapping ions on the duct wall is utilized, there is also an effect of preventing ion wrapping with respect to the electron beam. Due to these effects, the life of the electron beam can be extended.

FIG. 4 shows another embodiment. In this embodiment, contrary to the case of FIG. 3, the grounded beam duct side has a positive potential, that is, the anode, and the absorber side has a negative potential, that is, the cathode. Therefore, in this embodiment, the photoelectrons and the ions which are trapped by the absorber and do not collide with gas molecules or ions
Secondary electrons are trapped in the beam duct. The effect of trapping gas molecules or the effect of preventing ion trapping is the same as in the case of FIG. 3, and the life of the electron beam is also prolonged.

As yet another embodiment, the absorber 5 shown in FIG.
In some cases, a low photodesorption coefficient material made of oxygen-free copper, aluminum, or the like having an extremely high purity is used as the material. In this case, the amount of gas released by SOR light irradiation is originally reduced, which is more effective for improving the degree of vacuum.

〔The invention's effect〕

According to the present invention, gas molecules and ions emitted by SOR light are captured by the wall surface or the absorber, the degree of vacuum in the beam duct is improved, and ion trapping is prevented. There is an effect that can be extended.

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention, a sectional view of a beam deflecting portion of a SOR device, FIG. 2 is an enlarged sectional view of a beam duct near an absorber, and FIG. 3 is an enlarged sectional view of a beam duct of this embodiment. FIG. 4 and FIG. 4 are enlarged sectional views of a beam duct of another embodiment. 1 ... Bending electromagnet, 2 ... Beam duct, 3 ... Electron beam, 4 ... SOR light, 5 ... Absorber, 6 ... Emitted gas molecule, 7 ... Photoelectron, 8 ... Reflected light, 9 ... Emitted gas molecules by reflected light, 11 …… Built-in pump chamber, 12 …… Built-in pump, 14 …… Lead wire, 15 …… Current introduction terminal, 16 …… DC power supply, 20 …… Spiral electron orbit, 21 ……ion.

Front page continued (72) Inventor Takashi Ikeguchi 502 Jinmachicho, Tsuchiura-shi, Ibaraki Hitachi Machinery Research Laboratory, Inc. (72) Inventor Manabu Matsumoto 502 Jinmachi-cho, Tsuchiura-shi, Ibaraki Hitachi Machinery Research Institute, Inc. (72) ) Inventor Toshiaki Kodai 502, Kintate-cho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Shunji Kakiuchi 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi Ltd. (72) Invention Ito Satoshi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Tatsu Murashita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-62-180999 (JP, A) JP-A-62-200697 (JP, A) JP-A-62-110300 (JP, A)

Claims (1)

(57) [Claims] 1. A synchrotron radiation generator that is surrounded by a deflecting magnet and has a beam duct required for circulating charged particles. In the synchrotron radiation generator, the beam deflector is provided on a side of the beam duct which is not irradiated with the synchrotron radiation. A built-in chamber is provided, a window is opened between the built-in chamber and the beam duct, and a built-in pump is provided in the built-in chamber, and low light desorption is performed in the beam duct at a position irradiated with synchrotron radiation. A synchrotron radiation generating apparatus characterized in that a beam absorber made of a coefficient material is provided, the beam absorber and the beam duct are electrically insulated, and a DC voltage is applied between them.