JP2511991B2 - Synchrotron radiation generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a synchrotron radiation generator (hereinafter, abbreviated as SOR device), and particularly for obtaining a vacuum performance suitable for a small industrial SOR device. The present invention relates to a SOR device with an improved vacuum duct.

[Conventional technology]

Generally, in a SOR device, as described later in detail, a large amount of gas, which is proportional to the deflection angle, is emitted particularly in the deflection part of the charged particle beam by irradiating the vacuum wall with radiation (hereinafter abbreviated as SOR). It

The conventional SOR device is described in Proceedings of the Fifth, Symposium on Accelerator Science and Technology (1984), pages 234 to 236.
Page (Proceeding of the 5th Symposium on Accelerator
As discussed in Science and Technology (1984) p234-236), the overall size of the charged particle beam storage ring is equipped with a large number of deflection electromagnets, and the deflection angle per deflector is It is made small. For this reason, the gas released by the SOR is dispersed all over the charged particle beam orbit, and the amount of gas released per deflecting portion is reduced. Also, on both sides of the deflected beam duct,
Since a vacuum pump with a relatively large capacity in space can be installed, effective exhaust is obtained together with the built-in pump in the beam duct. Furthermore, in the SOR lead-out duct that guides the SOR to the outside, Nukurya Instruments and Method 177 (1980), pages 111 to 115 (Nuc
lear Instruments and Methods 177 (1980) p111-115)
As discussed in, the large SOR device has a small deflection angle, so the derived SOR has a small divergence angle.
Irradiation of SOR to the inner wall of the lead-out duct is avoided, and gas release due to SOR irradiation in the duct is prevented. This is very effective in differentially pumping the SOR beam line, which has a relatively high pressure, and the charged particle beam duct, which requires ultra-high vacuum.

[Problems to be solved by the invention]

However, when the SOR device is miniaturized into an industrial device, the deflection parts for extracting the SOR are arranged in a centralized manner in order to reduce the installation space restriction and the manufacturing cost. The deflection angle of is greatly expanded.

For example, if the SOR device is composed of two linear parts and two deflecting parts, the deflecting angle per deflecting part is 180 degrees, and the SOR from the inner wall surface of the charged particle beam duct in one deflecting part is accompanied by this. The amount of gas released by this is about 10 times that of a large SOR device.

Also, because the number of deflecting parts is limited, multiple SOR loading ducts will be installed in one deflecting part to derive SOR. However, since the SOR spreading angle in the SOR derivation duct is large The inner wall is illuminated by the SOR, and a large amount of gas is released even in the SOR outlet duct.

Therefore, in the case of a small SOR device, a large amount of gas is intensively generated even though the space for installing a vacuum pump is restricted due to the miniaturization, so the charged particle beam duct cannot be sufficiently evacuated. There is a problem that the desired beam life cannot be obtained because the gas molecules hinder the orbital movement of the charged particles.

An object of the present invention is to provide a SOR device capable of extending the life of a charged particle beam and supplying a stable and strong SOR even when used in a small industrial SOR device.

[Means for solving problems]

The above object is to provide a deflection duct that forms a deflection portion of the beam of the circular orbit around which the charged particle beam revolves, and a radiation duct that is connected to the outer peripheral side of the deflection duct and extends in the tangential direction of the circular orbit. In a synchrotron radiation light generation device including at least one lead-out duct for leading out light, the lead-out duct has a divergent shape in which an inner width is gradually increased toward an outer peripheral side on a circular orbital surface of the beam. And a divergence angle of the divergent shape is made larger than a divergence angle of the radiated light passing through the inside of the lead-out duct, and a vacuum exhaust device for evacuating the inside of the lead-out duct is provided in the vicinity of the outermost periphery of the lead-out duct. To be achieved.

[Action]

According to the present invention, by making the spread angle of the lead-out duct larger than the spread angle of the SOR, the inner surface of the lead-out duct is not irradiated with SOR, so that the inside of the lead-out duct can be maintained in an ultrahigh vacuum. Also, even if the SOR is irradiated to the SOR transportation duct connected to the outer circumference of the outlet duct and the gas is released, the released gas can be immediately exhausted by the vacuum exhaust device provided near the outermost periphery of the outlet duct. It is possible to prevent the released gas from lowering the vacuum degree in the deflection duct. Furthermore, since the inside of the lead-out duct can be maintained at an ultra-high vacuum, the vacuum exhaust device provided near the outermost periphery of the lead-out duct also contributes to the vacuum exhaust in the deflector duct, so that the inside of the deflector duct can be made to a higher vacuum. Can be maintained.

Therefore, it is possible to suppress the charged particle beam that orbits the circular orbit from colliding with the gas component in the deflection duct and disappear, and thus it is possible to extend the life of the charged particle beam.
As a result, a desired beam current can be stably circulated, so that a stable SOR having high strength can be supplied.

〔Example〕

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

FIG. 1 shows the deflecting portion of a small industrial SOR device provided with the SOR lead-out duct according to the present invention.

In the present embodiment, the deflection angle of the charged particle beam per deflecting portion is set to 180 degrees for the purpose of downsizing, and the entire SOR device has the deflecting portions shown in two positions on the left and right, and the middle portion thereof is a linear portion. By connecting with, the circular orbit of the charged particle is configured to be an elliptical orbit.

In the figure, reference numeral 1 is a deflection beam duct for orbiting charged particles along an orbit A, and the periphery thereof is surrounded by an iron core 3 of a deflection electromagnet for controlling a deflection motion of the charged particle beam.

FIG. 2 is a sectional view taken along line XX of FIG.
The cross-sectional shape of is shown. As shown in the figure, on the inner peripheral side of the deflection duct 1, there is a pump chamber 1c which is separated by a partition plate 1a, and a non-evaporating getter pump 2 is provided all over the entire 180 degrees.

On the other hand, on the outer peripheral side of the deflection duct 1, four SOR derivation ducts 4 branched from the outer peripheral wall of the duct 1 are parallel to the orbital plane (the plane including the orbit A) of the charged particle beam and the orbit A Tangentially, it extends through the iron core 3 and is connected to the SOR beam line 6 by a flange 4b at the outer end.

FIG. 3 shows the YY cross section of FIG.
An ion pump 5a and a titanium getter pump 5b are directly installed on the side surface of the SOR lead-out duct 4 between the outer wall and the flange 4b.

As can be seen from FIG. 1 and FIG. 3, the SOR lead-out duct 4 is a flat spreading duct in which only the cross section parallel to the charged particle beam orbital plane expands as it extends outward from the outlet 4a at the branch point. There is.

FIG. 4 shows the ZZ cross section of FIG. 3 and shows the relationship between the divergence angle of the SOR lead-out duct and SOR. Of the SOR radiated tangentially from the charged particle beam passing through the orbit A, the divergence angle θ _s equal to the deflection angle θ _b, which is obtained by the geometric relationship from the size of the frontage of the outlet 4a and the orbital curvature, SO
Although R is led to the SOR beam line 6 through the SOR lead-out duct 4, the spread angle θ _d of the SOR lead-out duct has a relationship of θ _d > θ _s (1), that is, the charged particle beam trajectory of the SOR lead-out duct. The divergence angle of the cross section parallel to the plane is slightly larger than the divergence angle of the same cross section of the SOR.

Next, the operation and effect of this embodiment will be described.

When the SOR irradiates the vacuum wall, the gas inside the material excited by the high-energy SOR is released, and the photoelectrons emitted by the light irradiation stimulate the wall surface, which is orders of magnitude higher than in ordinary thermal desorption. Releases a large amount of gas. Its release amount of gas, the photon number n _p of SOR applied per unit time, is by connexion estimated Q = ηn _p ... (2) When the elimination coefficient of the material pieces Yes eta, photon number n _p Increases in proportion to. Since n _p is proportional to the deflection angle of the charged particle beam, that is, the larger the deflection angle, the larger the amount of released gas per deflecting section.

In this embodiment, about half of the total gas released by SOR is 1
It is concentratedly emitted to the deflection part, but since the SOR is led out by the four SOR lead-out ducts, the released gas for a deflection angle of 4θ _b is released inside the SOR lead-out system and remains there. Are emitted into the deflected beam duct.

In the deflected beam duct 1 of FIG. 2, the gas B released by SOR irradiating the outer peripheral wall 1d of the duct 1 flows into the pump chamber 1c through the gas passage 1b, and In addition to being exhausted by the evaporative getter pump 2, it is also exhausted to both ends of the duct and is also exhausted by an ion pump or the like provided in a linear beam duct connected to the same, although not shown. . The partition plate 1a is for preventing the exhausted gas from being re-emitted by reflected light or photoelectrons stimulating the non-evaporable getter pump 2.

On the other hand, in the SOR derivation system, as shown in FIG.
Is not directly radiated to the SOR derivation duct due to the relationship of the equation (1), but is radiated to the inner wall of the subsequent SOR beam line 6. Most of the released gas C is SOR due to the influence of this light and photoelectrons.
It is emitted to the beam line 6 side and is exhausted by the pumps 5a and 5b and the pump provided in the SOR beam line 6 (not shown).

FIG. 5 shows the pressure distribution in the deflector duct formed by the above-mentioned exhaust.

For comparison, the distribution curve 7 in the figure shows the pressure distribution in the case of using the unexpanded SOR derivation duct in which the SOR derivation port 4a is extended as it is. Since the gas is emitted into the duct due to the irradiation of the gas, the duct conductance is small, and the effective pumping speed of the vacuum pumps 5a and 5b for the emitted gas is small, so that a part of the emitted gas flows out to the deflection duct side. become. In the deflected beam duct, a large amount of gas is discharged, but the installation space for the vacuum pump is narrow, so the pump capacity is limited. In addition, since the gas passage 1b is small, the effective pumping speed of the vacuum pump 2 is small. When the released gas flows in, sufficient exhaust cannot be performed and the pressure rises.

On the other hand, when the SOR derivation duct is a widened duct, as shown by the distribution curve 8, the conductance increases due to the expansion of the flow path, so that the effective pumping speed of the vacuum pumps 5a and 5b increases. Further, since the gas emission source approaches the vacuum pumps 5a and 5b, the exhaust efficiency of the vacuum pump is improved. Further, since the gas released in the SOR derivation duct is very small, the maximum value of the pressure cannot exist in the duct, and the gas emitted from the deflected beam duct 1 is also exhausted.
Therefore, the exhaust capacity in the deflected beam duct is improved and the pressure in the duct is reduced.

Further, according to the present invention, the source of the gas released by the SOR is located outside the outer circumference of the iron core 3 of the deflection electromagnet, but the vacuum pumps 5a and 5b having a large exhaust capacity are installed because the vacuum pumps are easy to install there. As a result, the exhaust capacity for the deflected beam duct is increased more and more, and the pressure is greatly reduced as shown by the distribution curve 9.

Similar to the large-scale SOR device, a slit is provided at the SOR outlet 4a to squeeze the light so that the SOR outlet duct is a parallel duct with a width that does not irradiate the SOR. Although the effect of
Since the OR spread angle is large, the width of the duct becomes very large, and therefore the iron core near the deflected beam duct is removed, resulting in non-uniform magnetic flux density and unstable orbital motion of the charged particle beam. become. That is, according to the present invention, there is an advantage that the vacuum exhaust performance can be improved without adversely affecting the circulation of the charged particles.

The above-mentioned improvement of the exhaust performance by the SOR lead-out duct works particularly effectively in the initial startup operation of the SOR device.

 Next, this effect will be described.

The desorption coefficient η of the gas shown in the above equation (2) is related to the cumulative number of photons N _p obtained by integrating the number of photons η _p with time, and decreases almost in inverse proportion to N _p on the logarithmic graph. Tend to do.
That is, as the cumulative value of the number of photons irradiated after long-term operation increases, the wall surface is cleaned and the amount of released gas decreases, and the pressure in the deflected beam duct also decreases. , The amount of emitted gas is very large and the pressure in the deflected beam duct is high because the irradiation history of photons is shallow. Since the charged particle beam lifetime is inversely proportional to the orbital pressure, the beam current cannot be maintained, and the charged particles are frequently repeatedly incident. Therefore, since the number of irradiation photons N _p does not increase in the early stage of operation, the desorption coefficient η does not decrease and the pressure drop with time is slow, so that a large exhaust gas with excellent exhaust performance is obtained.
Even in the SOR device, it takes a yearly startup operation time to obtain a desired beam current. According to the present invention, even in a high pressure region, the same exhaust performance can be exhibited and the pressure can be lowered. Therefore, the extension of the life of the charged particle beam and the reduction of the emitted gas act synergistically, and the desired beam current can be promptly obtained. can get.

In addition, the non-evaporable getter pump installed in the deflected beam duct shortens the life of the pump itself when used in a high pressure range. In the high pressure region, the operation in which the non-evaporable getter pump 2 is temporarily stopped becomes possible.

Furthermore, according to the present invention, other effects can be obtained in addition to the exhaust performance.

The SOR irradiation surface is a high heat source because it is irradiated with high-energy photons, and is usually cooled from the back surface. Even in the SOR derivation duct, the inside of the duct is surrounded by a high vacuum, and the outside is surrounded by the iron core of the bending electromagnet, so the heat transfer condition is very bad.Therefore, cooling is required when SOR is irradiated. In the invention, since the inner surface of the duct is not irradiated with SOR, it is possible to omit the cooling in the place where the space is narrow.

Further, depending on the SOR user, a large installation space for the spectroscope and the mirror, and for other purposes, a SOR with a large divergence angle is required, but according to the present invention, the SOR radiated from the SOR outlet is Since it is possible to derive everything into multiple parts without messing up in the middle of the SOR derivation duct, there is an advantage that SOR can be effectively used.

In the embodiment described above, the SOR derivation duct was composed of four, and the titanium getter pump and the ion pump were used together per one duct, but the number of SOR derivation ducts is determined by the request of the SOR user. However, the amount of gas released in the deflected beam duct and the exhaust capacity toward the SOR derivation duct change depending on the number of attachments. However, if the exhaust capacity of the above-mentioned pump is appropriately selected, almost the same effect can be obtained. The same applies to the built-in pump in the deflection beam duct, and in addition to the non-evaporating getter pump described in the embodiment, a distributed ion pump utilizing the magnetic field of the deflection electromagnet may be used. That is, the present invention does not limit the number of SOR derivation ducts, the type of pumps, the number of pumps, and the like.

Further, in the embodiment, the deflection part having a deflection angle of 180 degrees is shown. However, since this deflection angle is the most severe condition in terms of vacuum pumping performance, the condition of equation (1) is satisfied even when the deflection angle changes. Only by changing the divergence angle of the SOR derivation duct so as to satisfy the requirement, it can be applied without any special innovation.

〔The invention's effect〕

As described above, according to the present invention, the inside of the lead-out duct can be maintained in an ultrahigh vacuum by making the spread angle of the lead-out duct larger than the spread angle of the SOR. Further, by providing the vacuum exhaust device in the vicinity of the outermost periphery of the lead-out duct, it is possible to prevent the release gas generated on the outer peripheral side of the lead-out duct from lowering the degree of vacuum in the deflection duct. Further, the vacuum exhaust device provided near the outermost periphery of the lead-out duct also contributes to the vacuum exhaust in the deflection duct, and the inside of the deflection duct can be maintained at a higher vacuum. Therefore, it is possible to extend the life of the charged particle beam that orbits the orbit, and it is possible to supply a stable and stable SOR.

[Brief description of drawings]

FIG. 1 is a plan view of a deflecting portion showing an embodiment of a synchrotron radiation light generating apparatus of the present invention, FIG. 2 is a sectional view taken along line XX in FIG. 1, and FIG. 3 is YY in FIG. FIG. 4 is a sectional view, FIG. 4 is a sectional view taken along line ZZ in FIG. 3, and FIG. 5 is a characteristic diagram showing a pressure distribution of the deflection section according to the present invention. 1-deflecting part charged particle beam duct (deflecting beam duct), 1a ... partition plate, 1b ... gas passage, 1c ... pump chamber, 1d ... wall, 2 ... non-evaporable getter pump, 3 ... iron core 4 ... SOR outlet duct, 4a ... outlet, 4b ... flange, 4c ... wall, 5a ... ion pump, 5b ... titanium getter pump, 6 ... SOR beamline, 7,8,9 ...... Pressure distribution curve, A …… charged particle beam orbit, B, C …… released gas.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Ikeguchi, 502 Jinrachicho, Tsuchiura-shi, Ibaraki Hitachi Machinery Research Laboratory, Inc. (72) Shinjiro Ueda, 502, Jinmachi-cho, Tsuchiura, Ibaraki Hitachi, Ltd. Inside the laboratory (72) Inventor Toshiaki Kodai 502 Jinrachicho, Tsuchiura City, Ibaraki Prefecture Hitachi Machinery Research Laboratory (72) Inventor Tadashi Sonobe 3-1, 1-1 Sachimachi, Hitachi City, Ibaraki Inside Hitachi Factory, Hitachi Ltd. (72) Inventor Tatsu Murashita No. 3 Morinosato Wakamiya, Atsugi City, Kanagawa Prefecture, Japan Atsugi Telecom Research Laboratories, Nippon Telegraph and Telephone Corporation (72) Atsushi Ito No. 3 Morinosato Wakamiya, Atsugi City, Kanagawa Prefecture, Japan Telegraph and Telephone Corporation (72) Inventor, Kazuo Kuroishi, 2-9-1, Aize-cho, Hitachi-shi, Ibaraki Japan Service Engineering in Inc. (56) References Patent Sho 62-216200 (JP, A) JitsuHiraku Akira 63-79100 (JP, U)

Claims (1)

(57) [Claims] 1. A deflection duct forming a deflection portion of the beam of a circular orbit around which a charged particle beam orbits, and a deflection duct connected to an outer peripheral side of the deflection duct and extending in a tangential direction of the circular orbit to extend from the beam. In a synchrotron radiation generator including at least one lead-out duct for leading out synchrotron radiation, the lead-out duct has a widening tip on the circular orbital surface of the beam, the inner width of which widens toward the outer peripheral side. A evacuating device that has a shape, a divergence angle of the divergent shape is made larger than a divergence angle of radiated light passing through the lead-out duct, and a vacuum exhaust device for evacuating the inside of the lead-out duct is provided near the outermost periphery of the lead-out duct. A synchrotron radiation generator characterized by.