JPH02295100A - Synchrotron radiation generator - Google Patents

Abstract

PURPOSE:To make an insertion device function effectively in a radiation generator which takes an in-ring accelerating method of low energy incidence by providing two vertical cross sections of different heights, in a linear vacuum chamber through which charged particles pass linearly. CONSTITUTION:A vacuum chamber at a linear part is put in such structure that two chambers 11 and 12 wherein height dimensions of vertical cross sections are different adjoin each other, and deflecting magnets 13a-13d for curving the orbits of electrons are provided at both ends of it. By taking such structure, large height dimensions can be sought in the vacuum chamber. Even in the device by the in-ring accelerating method of low energy incidence, an insertion device requiring to suppress the height dimension of the vacuum chamber low can be installed. Hereby, even in the device by the in-ring accelerating method of low energy incidence, synchrotron radiation, which is different in spectrum and strength from the deflecting part, can be generated from an insertion device installed in the linear part.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to a synchrotron radiation light (hereinafter referred to as SOR light) generation device, and particularly relates to a vacuum chamber structure in a charged particle beam straight-travel portion of an SOR light generation device. It is related to.

(2) Conventional technology When a charged particle such as an electron or positron that has been accelerated to a speed close to the speed of light is bent in its traveling direction, the wavelength range becomes X-rays along the straight direction of the particle trajectory due to the action of bremsstrahlung. It is known that SOR light in the infrared range is generated from

An example of a conventional SOR light generation device is shown in FIG.

It is composed of a plurality of deflection sections 1 and a straight section 2 connecting the deflection sections 1, and has a configuration in which charged particles (hereinafter referred to as electrons) circulate in a vacuum chamber 3 maintained at a high vacuum. ing. A deflection magnet 4 that bends the traveling direction of electrons is installed in the deflection section 1, and a quadrupole magnet 5 that converges the electron beam, a multipole magnet (not shown in the figure), an RF cavity, etc. are installed in the straight section 2. . In this configuration, SOR light is generated in the linear direction of the electron trajectory of the deflection unit 1. Book SO
When the electron energy and deflection magnetic field are fixed, the characteristics of R light also become constant. Therefore, an insertion device 6 such as a wiggler or an insulator is installed in the straight section 2 in order to increase the strength of the SOR destination or make it monochromatic even with the same electron energy.

When electrons pass through the magnetic field formed by the wiggler or undulator, the electrons are affected by bremsstrahlung radiation, similar to the deflection unit 1 described in "-", and SOR light is generated in the direction in which the electrons travel straight. The SOR light generated from the wiggler has a spectral distribution shifted to the shorter wavelength side compared to that generated from the deflection section 1, and the SOR light generated from the undulator is strong interference light. In this way, the Inri Schondehuis is an SO with different characteristics from the deflection section 1.
Since it can generate R light, it has become an indispensable device in fields such as spectroscopy.

On the other hand, as one of the methods for accumulating high-energy electrons in the SOR light generator, there is an in-ring acceleration method. This is a method in which low-energy electrons are input from an input accelerator such as a linac, accelerated to the final energy in an SOR light generator, and then directly transferred to an accumulation state. The lower the incident energy, the smaller the incident accelerator, so the in-ring acceleration method is extremely effective in downsizing the device. For example, if the incident energy is lowered to around 15 MeV, the total length of the linac will be reduced to about 2 m.

The distribution of the number of electrons in the vertical cross section of an electron beam is a Gaussian distribution, and it is difficult to accurately express the size of the beam. Let express the diameter of the beam. When the incident energy is about 15 MeV, the diameter of the incident electron beam is several Inm~
It spreads to 10mm. As the electron beam is accelerated to a high energy level, the diameter of the electron beam becomes narrower due to the effects of adiabatic attenuation and radioactive decay, eventually reaching about 1 mm.

The intensity of the SOR light is determined by the number of electrons that have been accelerated to high energy and accumulated as they are, that is, the accumulated current value. In the in-ring acceleration method, unlike the case of injecting high-energy electrons, it is difficult to inject low-energy electrons multiple times. Therefore, it is necessary to accelerate the low-energy electrons to the final energy with only one injection. In order to obtain strong SOR light, it is necessary to prevent the dropouts during the acceleration of incident low-energy electrons, that is, undamped electrons with a widened beam diameter, from colliding with the inner wall of the vacuum chamber.
It is important to keep it as low as possible.

In addition, the movement of electrons circulating inside the SOR light generator,
When viewed from the vertical section of the vacuum chamber, it is horizontal. It vibrates in both vertical directions and is always inside the vacuum chamber tC,-
There is no C. Particularly in the case of low-energy electrons such as in the in-ring acceleration method, it is necessary to consider the generation of COD due to the earth's magnetism and the spread of the beam diameter due to the above-mentioned non-damped electrons.

For the above reasons, from the standpoint of beam dynamics, it is considered necessary to ensure a height of the vacuum chamber of 7σ to 10σ, specifically at least 50 to 60 mm.

On the other hand, in the case of an undulator, a linear vacuum duct 1- is sandwiched between an array of magnets from above and below, and electrons passing through the gap are periodically deflected by the upper and lower magnets, thereby generating strong interference light. .

The intensity of the interference light is determined by the number of periods of periodically arranged magnets and the magnetic field strength of those magnets. In order to improve the intensity of interference light, it is effective to increase the magnetic field intensity.

The magnetic field strength and the magnetic pole spacing are inversely proportional to each other, and in order to obtain strong interference light, it is necessary to reduce the gap between the upper and lower magnet rows, that is, the height of the vacuum chamber, as much as possible. By the way, the magnet gap of the conventional insertion device is 2
Most of them are 0 to 30 mm, and this value is about half the height of the vacuum chamber required for the intra-ring acceleration method of low energy incidence. On the other hand, if the magnet gap of the insertion device is set to 50 to 60 mm, the magnetic field strength decreases to half of the conventional strength, making it impossible to obtain interference light of sufficient strength. For this reason, in order to make the insersigon device function effectively in a synchrotron radiation generator that uses an in-ring acceleration method with low energy incidence, an unprecedented vacuum chamber structure is required.

(3) Purpose of the Invention The present invention relates to a charged particle SOR light generation device, in which an insertion device can be inserted into the straight part of the device, and synchro 1-ron synchrotron synchrotron synchrotron radiation, which uses an in-ring acceleration method with low energy incidence, is provided. The purpose is to realize a generator.

(4) Structure of the invention (4-1) Differences between characteristics of the invention and conventional technology Conventional SOR
In a light generating device, particularly in an SOR light generating device that uses an in-ring acceleration method with low energy incidence, it is necessary to increase the height of the vacuum chamber in order to reduce the dropout of electrons. For this reason, the straight section of the vacuum chamber in which the insertion device is to be installed is a straight pipe with a high and uniform cross-sectional height, and it is difficult to install the insertion device in that state.

In contrast, in the present invention, the vacuum chamber in the straight section in which the insertion device is installed has two levels of height: a high chamber through which electrons pass when the incident energy is low; It has a structure that combines a "low-height chamber" that accelerates the beam to high energy and passes it when it is focused.The insertion device is used in combination with the "low-height chamber". By doing so, the function can be demonstrated.

In the present invention, deflecting magnets for bending the traveling direction of electrons are provided at both ends of the vacuum chamber having such a composite structure. Furthermore, in the present invention, bellows can be provided at both ends of the vacuum chamber of the composite structure so that it is movable.

With this configuration, low-energy electrons incident on the SOR light generator first pass through the vacuum chamber on the higher side. As the electron energy increases, the electron beam diameter becomes narrower. The narrower beam allows the electrons to pass through a lower vacuum chamber. The timing of moving the electron orbit may be when the energy of the electron is in the middle of acceleration or when the electron has reached its final energy.

As a result, even in an electron storage ring that uses an intra-ring acceleration method with low energy incidence, it is possible to install an insertion deheith with a narrow gap between magnets.

In addition, in the present invention, an optical absorber made of a material that releases less gas due to optically stimulated desorption is provided on the inner surface of the linear vacuum chamber to reduce the amount of gas released due to optically stimulated desorption and maintain a good degree of vacuum in the vacuum chamber. can be maintained in the same condition.

(4-2) Example (Example 1) Fig. 2 is a plan view of an embodiment of the vacuum damper structure of the straight section according to the present invention, Fig. 3 is a sectional view taken along plane AA of Fig. 2, and Fig. FIG. 4 is a sectional view taken along the line B--B in FIG. 2.

As shown in FIGS. 2 and 3, the vacuum chamber structure of this embodiment has a high-height chamber 11 (hereinafter referred to as a high chamber) and a low-height chamber 12 (hereinafter referred to as a low chamber). They are arranged adjacent to each other in parallel, and the interiors of both are spatially connected as shown in FIG. Taka Champa 1
1 has a straight part and two deflection parts, and the low chamber 12 has only a straight part. Both ends 14a of the vacuum chamber
, 14b is connected only to the high chamber 11, and the low chamber 12 joins the high chamber 11 before reaching both ends 14a, 14b of the vacuum chamber.

The point where the high chamber 11 and the low chamber 12 meet in this way corresponds to the starting point when bending the traveling direction of electrons. There are deflecting magnets 13a to 1 as illustrated in FIG.
3d and by changing their excitation conditions, it is possible to select which of the high chambers 11 and the low chambers 12 the electrons will pass through. For example, as shown in Figure 2,
When electrons e- travel downward from the north of the paper, if the magnetic fields of the deflecting magnets 13a and 13t are directed vertically downward at 13a and vertically downward at 13b, the electrons will move inside the high chamber 11. It passes through the orbit 15a of . Deflected borite 13a
, 13b by changing the excitation conditions of the high chamber 1.
Orbit 15a within 1 or orbit within low chamber 12]-
5b, electrons can pass through any of them. Although the deflection magnets 13a and 13b have been described above, the functions of the deflection magnets 13c and 13d are also exactly the same.

S where a vacuum chamber with the above structure is installed on a straight section
When the in-ring acceleration method with low energy incidence is applied to the OR light generator, the electrons incident on the SOR light generator first excite the deflection magnets 13a to 13d so as to pass through the trajectory 15a in the high chamber 11. control. The incident electrons are accelerated within the ring, their energy increases, and when the electron beam reaches a narrow state, the deflection magnet]. By gradually changing the excitation of 3a to i3d, the orbit of the electron is changed to the orbit i in the lower chamber 12.
15b. When the energy of the electrons passing through the low chamber 12 reaches the final energy, a magnet array of the insertion height is inserted into the low chamber 12 from above and below. If the magnet is in an excited state, S○R light will be generated along the straight direction of the electrons.

(Example 2) When the inner wall of a vacuum chamber is irradiated with SOR light, a large amount of gas is released from the inner wall surface and surface layer due to a phenomenon called photostimulated desorption, which may worsen the vacuum inside the chamber. Are known.

Also in the first embodiment of the present invention, the deflecting magnets 13a to 1
3d bends the traveling direction of the electrons, and when the energy of the electrons increases during the process of acceleration within the ring and SOR light begins to be generated, gas emission occurs due to the above-mentioned optically stimulated desorption. This phenomenon is particularly noticeable in stainless steel, which is the most commonly used material for vacuum chambers.

A second embodiment of the invention is shown in FIGS. 5 and 6.

FIG. 6 shows a cross section taken along the line C--C in FIG. 5. The basic structure of the vacuum chamber is the same as in FIG. The inner surface of the vacuum chamber where the SOR light is irradiated is coated with abrasive materials that release less gas due to optically stimulated desorption, specifically oxygen-free steel and aluminum 1.
, or an optical absorber 21 made of silicon or the like. According to this, the SOR light generated when the traveling direction of electrons is bent by the deflection magnet is irradiated onto the optical absorber 21 without being irradiated directly onto the inner wall surface of the vacuum chamber. The amount of gas released from the optical absorber 21 is much smaller than that of stainless steel, which is the material of the vacuum chamber, and therefore the degree of vacuum within the vacuum chamber can be maintained at a good level even when SOR light is generated.

The portion irradiated with the SOR light receives the energy of the SOR light and causes a temperature rise. As the number of accumulated electrons, that is, the current value increases, the temperature rise also increases, which may lead to softening and melting of the material itself. In order to prevent this, in this embodiment, a cooling pipe 22 is provided in the optical absorber 21, and a coolant is passed through the pipe 22 to cool the optical absorber 21.
1 is forcibly cooled. As a refrigerant, cooling water is inferior in terms of cooling efficiency, but low-temperature gases such as Freon can also be expected to have a cooling effect. Note that when it is not possible to use an optical absorber due to spatial constraints, cooling piping may be arranged on the outer wall of the vacuum chamber to perform forced cooling.

Furthermore, in this embodiment, distributed vacuum pumps 23 are installed along the electron traveling direction of the vacuum chamber.

As the distributed vacuum pump 23, a DTP that utilizes the leakage magnetic field of a deflection magnet is well known, but in this embodiment, since it is operated in the absence of a magnetic field, a non-evaporative getter bomb is suitable. Light absorber 21 already mentioned
By using the distributed type vacuum bomb 23 in combination, it becomes possible to maintain the degree of vacuum in the vacuum chamber in a good state.

If it is difficult to install a distributed type vacuum pump due to constraints on installation space, a conventional centralized type vacuum pump, such as a spaso ion bomb or a titanium getter pump, may be installed at an appropriate location. In this embodiment, the distributed vacuum pump is provided on the lower surface of the high chamber for convenience, but it is obvious that it can be mounted on either side of the high chamber or on the side of the high or low chamber. .

(Example 3) FIG. 7 shows a third embodiment related to the present invention.

The structure of the vacuum chamber consists of a high chamber 31 and a low chamber 3.
2 are adjacent to each other, and the shape of the DD cross section is basically the same as that of the first embodiment shown in FIG. At both ends 33a and 33b of the vacuum chamber, heroses 34a and 34b are provided which are movable in the horizontal plane of the paper. The cross-sectional shape of the bellows may be any shape, such as a circular oval, a race/rack shape, or a rectangle, but the opening cross-sectional area must be such that it does not impede the passage of electrons.

A case will be described in which low-energy electrons are incident on an SOR light generation device in which a vacuum chamber having the above configuration is installed in a straight section using an in-ring acceleration method. In this embodiment, the electrons always pass through a straight trajectory 35. Therefore, the chamber centers of the high chamber 31 in the case of low energy and the low chamber 32 after acceleration to high energy are aligned with the linear trajectory 35, respectively. That is, by utilizing the movable function of the bellows 34a and 34b in the horizontal plane, vacuum is applied in the direction of arrow A in FIG. 7 in the case of low energy, and in the direction of arrow B in the figure in the case of high energy. Move the chamber. Thereby, it is possible to realize a vacuum chamber in which an insertion device can be installed without using a deflecting magnet to bend the trajectory.

Furthermore, by superimposing the deflecting magnet described in Embodiment 1 on this embodiment, the amount of movement of the vacuum chamber by the bellows can be reduced, and even if the amount of excitation of the deflecting magnet is weakened, the same effect can be expected. I can do it.

(5) Effects of the Invention As explained above, in the present invention, the vacuum chamber in the straight section of the SOR source generator has a structure in which two chambers having different vertical cross-sectional height dimensions are adjacent to each other, and both ends of the vacuum chamber are A deflection magnet is installed to bend the trajectory of the electrons. By adopting such a structure, it is necessary to keep the height dimension of the vacuum chamber low even in the SOR light generation device using the "low energy intra-ring acceleration method" which requires a large height dimension in the vacuum chamber. It is possible to install an insertion deheis.This allows even for a SOR light generation device using the in-ring acceleration method of a low-energy person'J=1, the deflection part can be separated from the deflection part by an insertion deheis installed in a straight section.・It is possible to generate SOR light with different intensity and intensity.The lower the incident energy, the more compact the incident accelerator can be, which is especially useful for industrial applications where there are many space constraints. This is advantageous.In addition to miniaturization,
If it is also possible to install an insertion device, it is possible to further expand the uses of the SOR light generation device as a multipurpose SOR light source.

Furthermore, by arranging bellows near both sides of the linear vacuum chamber to enable movement of the vacuum chamber,
It is possible to realize a vacuum chamber in which an insertion device can be installed without using a deflecting magnet to bend the trajectory.

Furthermore, in the present invention, an optical absorber made of a material that releases less gas due to optically stimulated desorption is provided on the inner surface of the linear vacuum chamber, thereby reducing the amount of gas released due to optically stimulated desorption and increasing the degree of vacuum in the vacuum chamber. Can be maintained in good condition.

[Brief explanation of drawings]

FIG. 1 is an arrangement diagram showing an example of the configuration of a conventional electron storage ring, FIG. 2 is an arrangement diagram showing an example of the vacuum chamber of the linear part of the electron storage ring in the present invention, and FIGS.
The figure is a cross-sectional view of the vacuum chamber shown in Fig. 2, Fig. 5 is a longitudinal sectional view showing an example of a vacuum chamber in which a light absorber is installed as a second embodiment of the present invention, and Fig. 6 is a cross-sectional view of the vacuum chamber shown in Fig. 5. FIG. 7 is a cross-sectional view of a vacuum chamber shown, and FIG. 7 is a front view showing an example of a vacuum chamber in which a bellows is arranged as a third embodiment of the present invention. ]... Deflection section, 2... Straight line section, 3... Vacuum chamber, 4... Deflection magnet, 5... Quadrupole magnet, 6... Insertion device, 11. 13...high chamber, 1.2. 32...low chamber, 13a-13d.
...Bending magnet, 14a, 14b, 33a, 33b...
Vacuum chamber end, 15a. l5b...orbital, 21.
・・Light absorber, 22・・Cooling pipe, 23・・Distributed vacuum pump, 34a, 34b・・Bellows, 35・
...straight trajectory.

Claims (3)

[Claims] (1) In a synchrotron radiation light generating device composed of a plurality of deflection parts and a straight part, the straight part vacuum chamber, through which charged particles pass in a straight line, has a structure having vertical cross sections of two different heights. A synchrotron radiation light generating device characterized by: (2) The synchrotron radiation light generating device according to claim 1, wherein bellows are arranged near both ends of the linear vacuum chamber to enable movement of the vacuum chamber. (3) The synchrotron radiation light generating device according to claim 1, characterized in that an optical absorber made of a material that releases less gas due to optically stimulated desorption is provided on the inner surface of the linear vacuum chamber. .