JPH11273900A - Radiation light generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the restriction of the wavelength region and the degradation of the intensity of radiation and maintain a high vacuum state by installing hollow beam dumps, with which at least their radiant light passing surfaces are formed from a thin film and each of their inside is evacuated separately from a vacuum container at a part, excluding a radiant light extracting part located on the side wall of a vacuum container that generates radiant light by the movement of charged particles along a curved track in the inside. SOLUTION: Small box-like hollow beam dumps 50 of which passing surfaces for synchrotron radiation (SR light) 12 from an accumulated electron beam 10 that advances into an arc-like form in an electron beam deflection part are thin film windows 52 made of Be or the like and which are cooled are installed at parts, excluding an SR light extracting port 24P of a sidewall 24S of an evacuating part 24. The SR light 12 from the SR light extracting port 24P is extracted without changes, and a gas generated by photoelectrons emitted by other SR light passing through the thin film windows 52 and striking against the side wall 24S in the beam dump 50 is evacuated by means of an auxiliary vacuum pump or the like separately from an evacuating part 24. A gas generated in the continuous space between the electron beam deflection part can be significantly reduced, with a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchrotron radiation device which generates radiation by moving charged particles along a curved orbit in a vacuum vessel, and more particularly to a synchrotron radiation (referred to as SR light). ) Suitable for use in generating
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation light generator capable of reducing gas generated by irradiation of radiation light in a vacuum vessel.

[0002]

2. Description of the Related Art A synchrotron radiation light generator that generates SR light by moving charged particles such as electrons and positrons along a curved orbit is known.

As shown in FIG. 5 (a plan view of a deflecting unit) and FIG. 6 (a cross-sectional view taken along the line VI-VI in FIG. 5), the synchrotron radiation light generating apparatus has a structure in which the accumulated electron beam 10 is formed in an arc shape. An electron beam deflecting unit 22, a vacuum exhaust unit 24 having an SR light extraction port 24P formed on a side wall for extracting the SR light 12 emitted from the accumulated electron beam 10 to the outside, and the vacuum exhaust unit 24 And a connecting portion 26 connecting the electron beam deflecting portion 22 and the electron beam deflecting portion 22. Here, the electron beam accumulating unit includes the deflecting unit 22 that generates SR light, and a straight traveling unit that does not generate SR light.

The accumulated electron beam 10 continuously generates SR light 12 in a tangential direction at a point where the electron beam is deflected, but except for a portion passing through an extraction port 24P, a vacuum vessel (specifically, evacuation). Part), which is blocked by the side wall 24S, and causes a large amount of outgassing.

[0005] In the emission gas generation, a high-energy photon irradiation to the metal surface layer includes a part of photoelectron emission and a part of emission of adsorbed molecules due to heat input, and the latter is reduced at an initial stage, whereas the former is large. At the same time, it takes time to decrease.
In the former, heating and baking of members (so-called baking)
Then, it cannot be reduced.

[0006] In such a synchrotron radiation light generating apparatus, the problem is that the SR
By irradiating the light 12, a large amount of gas emitted from the surface of the vacuum vessel is exhausted without propagating to the electron beam deflecting unit 22, and the electron beam accumulating unit is maintained in an ultra-high vacuum.

For this reason, a member called a beam dump 30 or a crotch (for example, pure copper dissolved in vacuum) called a beam dump 30 or a crotch is provided in a portion irradiated with the SR light 12, and cooled by water or the like to generate gas. We are trying to reduce it. In order to suppress the propagation of the generated gas to the electron beam deflecting unit 22, a connecting portion 26 having a small conductance is provided between the electron beam deflecting unit 22 and the vacuum exhaust unit 24.

Further, the vacuum exhaust unit 24 is provided with a built-in vacuum pump 32 such as a cryopanel, etc., and a discharge gas generated at the side wall 24S of the vacuum exhaust unit 24 and blocked by the connection unit 26. Is exhausted, and the inside of the vacuum vessel 20 is kept at an ultra-high vacuum.

In FIG. 1, reference numeral 34 denotes an auxiliary vacuum pump.

[0010] One of the basic performances of such a synchrotron radiation light generating device is a circulating life of a stored current. This is because, in an optimally adjusted operation state, an electron beam storing portion of the device is required. It is determined by the degree of vacuum. However, in the initial stage of operation, no matter how low the vacuum of the base is evacuated, a large amount of gas is generated by the accumulation of the electron beam and the irradiation of the SR container with the SR light, and the electron beam travels over the electron orbit. It is difficult to maintain a high vacuum.

Usually, in order to reduce this problem, a vacuum pump having a large pumping capacity is provided, and a material to be irradiated with SR light is selected / used with a material which emits less gas, and can be sufficiently cooled. Is being done,
There are fundamental limits to the reduction of the emitted gas of the beam dump 30 (or crotch) and the reduction of the conductance of the connecting portion 26,
Not enough effect. Eventually, the operation of the apparatus (that is, the irradiation of the SR light 12 to the beam dump 30) is repeated, and it is necessary to wait for the emission gas to decrease (called as withering). During this time, the circulating life of the stored electron beam 10 gradually increases from an extremely short state to a required / designed state, so that the amount of released gas is sufficiently reduced and the circulating life of the stored current is planned (designed). It takes several years to reach the desired length.

In order to solve such a problem, a baffle plate is provided so that the gas discharged from the inner wall of the vacuum vessel does not easily reach the electron accumulation trajectory, and differential exhaust is performed by a built-in pump in the middle. Have been done.

Further, the applicant filed Japanese Patent Publication No. 7-75200,
As shown by a dashed line in FIGS. 5 and 6, the inside of the vacuum vessel 20 is provided concentrically along the outer wall of the vacuum exhaust unit 24.
For example, partition by a partition wall 40 made of a beryllium thin film, SR
It has been proposed to separately evacuate the outside where the gas emitted by the light 12 is generated, for example, by a vacuum pump 42.

[0014]

However, in the prior art in which the generated exhaust gas is evacuated by a large-displacement vacuum pump while having a shape of a vacuum vessel in which the generated gas is difficult to reach the trajectory of the accumulated electron beam, the generated gas is generated. The released gas itself could not be significantly reduced, and it was difficult to keep the trajectory of the stored electron beam 10 at a high vacuum.

In the method proposed in Japanese Patent Publication No. 7-75200, it is difficult to manufacture and construct a material (for example, a beryllium film having a thickness of about 10 μm and having a large area) suitable for the partition wall 40, which has not been realized. . Further, in this method, all the SR light extracted and used from the synchrotron radiation light generator to the outside passes through the partition wall 40.
There has been a problem that only a limited wavelength region of the white SR light spectrum can be extracted to the outside, and the intensity also decreases.

The present invention has been made to solve the above-mentioned conventional problems, and maintains the degree of vacuum in a vacuum vessel at a high vacuum without limiting the wavelength range of emitted light or reducing the intensity. That is the task.

[0017]

According to the present invention, there is provided a synchrotron radiation generating apparatus for generating synchrotron radiation by moving charged particles along a curved orbit in a vacuum vessel. A hollow beam dump having at least a surface through which the radiated light passes is provided in a thin portion, and the inside of the hollow beam dump is separately evacuated to a vacuum separately from the inside of the vacuum vessel. It is a solution to the problem.

According to the present invention, of the generated SR light, the portion which is irradiated to the inner wall of the vacuum vessel and is not taken out and used outside, in other words, only the portion which causes gas release in the vacuum vessel,
Since the gas is introduced into the hollow beam dump and most of the gas emission due to the SR light is in the hollow beam dump, the electron beam can be maintained in an ultra-high vacuum on the storage trajectory. Further, since the quality of the SR light extracted and used outside the apparatus passes through an empty portion between the plurality of hollow beam dumps, the SR light can be extracted without any change.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In this embodiment, FIG. 1 (a perspective view showing a main part), FIG. 2 (a plan view of a deflecting unit), and FIG.
As shown in FIG. 5 and FIG. 6, in the synchrotron radiation light generator similar to the conventional example shown in FIG. 5 and FIG. A small box-shaped hollow beam dump 50 having a thin film window 52 made of, for example, beryllium is provided on a portion excluding the SR light extraction port 24P, and the surface through which the radiated light passes is provided. Alternatively, the inside of the hollow beam dump 50 is connected to, for example, an auxiliary vacuum pump 34 and evacuated to a medium to high vacuum separately from the inside of the evacuation unit 24 while cooling directly.

The other points are the same as those of the above-mentioned conventional example, and the description is omitted.

In this embodiment, the SR light extraction port 2
The SR light 12 traveling to other than 4P is guided into the hollow beam dump 50 through the thin film window 52,
Collides with the side wall of the substrate and emits photoelectrons.

The solid line S in FIG. 4 is an example of the spectrum of the SR light generated from the synchrotron radiation light generator.
For example, the spectrum after passing through a beryllium film having a thickness of 10 μm is indicated by a broken line S ′, and most of the high-energy spectra that cause photoelectron generation pass without generating photoelectrons on the surface of the thin film window 52 and have a hollow beam. Dump 5
Enter within 0. The spectrum that has passed through the thin-film window 52 is applied to the inside of the hollow beam dump 50 to generate photoelectrons.
Since the space is different from the above, the released gas is exhausted by the auxiliary vacuum pump 34 without affecting the stored electrons at all.

On the other hand, the spectrum that does not pass through the thin-film window 52 has low energy, does not generate photoelectrons, and only contributes as heat, so that the effect is reduced in a short time.

Therefore, the gas generated in the space continuous with the electron beam deflecting section 22 is greatly reduced by this structure, and when passing through a 10 μm beryllium film, 1/10
Estimated degree.

Although this principle is also shown in Japanese Patent Publication No. 7-75200, in Japanese Patent Publication No. 7-75200, all the SR light including the SR light to be extracted and used passes through the partition wall 40 and the spectrum changes. This is extremely difficult to realize because a large-area thin film is required, and a vacuum-tight space must be formed with the large-area thin film.

On the other hand, in the present invention, such a problem is solved by disposing an independent small box-shaped hollow beam dump in a portion of the side wall of the vacuum vessel other than the portion for extracting the SR light.

In the present embodiment, since the inside of the hollow beam dump 50 is evacuated by the auxiliary vacuum pump 34, a separate vacuum pump is not required and the configuration is simple. Note that a vacuum pump independent of the auxiliary vacuum pump 34 for evacuating the vacuum evacuation unit 24 can be provided.

Further, in the above embodiment, the present invention
Although the present invention has been applied to the synchrotron radiation light generator, the application target of the present invention is not limited to this.

[0030]

According to the present invention, since no partition is provided at the radiation light extraction portion on the side wall of the vacuum vessel, the spectrum of SR light extracted and used outside the apparatus is not impaired. Further, a large-area thin film is not required and can be easily realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part configuration of an embodiment of the present invention.

FIG. 2 is a plan view showing a deflection unit.

FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a diagram showing a comparison of spectra of synchrotron radiation before and after passing through a beryllium film.

FIG. 5 is a plan view showing a deflection unit of a conventional synchrotron radiation light generating apparatus.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Accumulated electron beam 12 ... Synchrotron radiation light (SR light) 20 ... Vacuum container 22 ... Electron beam deflection part 24 ... Vacuum exhaust part 24P ... Radiation light extraction port 24S ... Side wall 26 ... Connection part 32 ... Built-in vacuum pump 34 ... Auxiliary vacuum pump 50 ... Hollow beam dump 52 ... Thin film window

Claims (1)

[Claims] 1. A synchrotron radiation generating apparatus for generating synchrotron radiation by moving charged particles along a curved orbit in a vacuum vessel, wherein at least a synchrotron radiation is provided at a portion of the vacuum vessel side wall other than a synchrotron radiation extraction section. A radiation beam generating apparatus, comprising: a hollow beam dump having a thin film passing therethrough, wherein the inside of the hollow beam dump is evacuated to a vacuum separately from the inside of the vacuum vessel.