JPH0448600A - Synchrotron radiation apparatus - Google Patents

Abstract

PURPOSE:To lessen the number of electromagnets for deflection, make the circumferential length of an accumulation ring short and the whole size small and at the same time obtain a highly intense synchrotron radiation output by using a prescribed prior stage accelerator as well as a core of an electromagnet for deflection. CONSTITUTION:A prior stage accelerator 1 is composed of a linear accelerator to accelerate an electron at <=20MeV or a microtron to accelerate an electron at 60-140MeV. Each electromagnet 5 for deflection consists of a pair of magnetic pole parts 8, 9 which are in the opposite each other in the direction rectangularly crossing the electron orbit plane while having the electron orbit P between them and a yoke part 10 to connect the pair of the magnetic pole parts 8, 9 on the center axis of the electron orbit P and is so formed as to have a fan-like shape as a whole and at the same time it also consists of a core 6 whose width in the direction rectangularly crossing the electron orbit of the yoke 10 is set to be wider than that in the direction rectangularly crossing the electron orbit P of the magnetic pole parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a synchrotron radiation device capable of extracting electromagnetic waves emitted when high-energy electrons are deflected by a magnetic field.

(Prior Art) As is well known, the degree of integration of a semiconductor device is greatly influenced by the wavelength of an exposure light source. Currently, ultraviolet light and the like are used as exposure light, but the degree of integration with these lights is approaching its limit.

For this reason, research has recently been conducted on using highly directional electromagnetic waves (specifically soft X-rays) emitted when high-energy electrons are deflected by a magnetic field as exposure light, and research has already been conducted Several proposals have been made for synchrotron radiation devices capable of transmitting this light.

A synchrotron radiation device normally makes high-energy electrons accelerated by a pre-stage accelerator enter a storage ring maintained in a vacuum state, and deflects the incident electrons using a plurality of deflecting electromagnets installed along the storage ring. It is configured to rotate while being deflected and to extract the soft X-rays emitted during deflection.

By the way, a synchrotron radiation device is, for example, an LSI
There are still some points that need to be improved in order to make it easier to use in the manufacturing field. For example, in conventional synchrotron radiation equipment, the lifetime of low-energy electrons is extremely short, so the electrons are accelerated to several hundred MeV or more in a pre-stage accelerator, and these high-energy electrons are injected into a storage ring to gradually increase the rated value. Accelerate up to energy or 100 M
The system employs a method in which the energy is injected at less than eV and then rapidly accelerated to the rated energy within the storage ring.

However, in the former case, the front stage accelerator becomes larger, which inevitably increases the size of the entire device. In addition, in the latter case, when the electron flow is rapidly accelerated in the storage ring, a large eddy current is induced in the iron core that makes up the deflection electromagnet, and the demagnetization effect accompanying this eddy current increases the strength of the deflection magnetic field. decreases.

For this reason, it is not possible to increase the deflection angle per deflection electromagnet, which not only necessitates a large number of deflection electromagnets, but also makes it necessary to increase the circumference of the storage ring. In this case, there was also the problem of increasing the size of the entire device.

In addition, in conventional synchrotron radiation devices, the iron core of the deflection electromagnet is a so-called recutangular type, in which thin plates punched in the cross-sectional shape of the iron core are stacked in a fan shape along the electron trajectory. The so-called sector type is used, in which punched thin plates are stacked in a fan shape with a spacer interposed outside the deflection track, or the type is formed into a similar shape by machining.

However, in most of the iron cores, the magnetic pole width on the electron orbit side and the cross-sectional width of the return yoke portion are formed to be approximately the same. For this reason, the magnetic flux path area on the return side is small, which makes it difficult to raise the magnetic field to nearly 1.5 T, which is considered the maximum effective magnetic field of the iron core material.
It has been difficult to increase the strength of the deflection magnetic field, reduce the number of deflection electromagnets, and shorten the circumference of the storage ring.

(Problems to be Solved by the Invention) As described above, in the conventional synchrotron radiation device, it has been difficult to reduce the overall size and store sufficient electrons in the storage ring.

Therefore, the present invention makes it possible to downsize the front-stage accelerator, reduce the number of deflection electromagnets, and shorten the circumference of the storage ring, thereby making it possible to downsize the entire system and obtain high-intensity synchrotron radiation output. The purpose is to provide a synchrotron radiation device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the synchrotron radiation device according to the present invention uses a pre-stage accelerator to emit electrons at 20 Me
A linear accelerator that accelerates electrons below V or 60 to 140
A microtron accelerated to MeV is used. The deflecting electromagnet also has a pair of magnetic pole parts facing each other in a direction perpendicular to the electron orbit plane with the electron orbit in between, and a yoke part that connects the above pair of magnetic pole parts around the center axis of the electron orbit, as the iron core of the deflection electromagnet. The width of the yoke portion in the direction perpendicular to the electron trajectory is set larger than the width of the magnetic pole portion in the direction perpendicular to the electron trajectory.

(Function) According to the conventional theory, the electron lifetime τa is extremely short in the low energy region. Based on this established theory, conventional synchrotron radiation devices use a large pre-accelerator as described above, or adopt a method in which the radiation is introduced at 100 MeV or less and then rapidly accelerated in a storage ring.

However, according to the research conducted by the present inventors, it was found that this established theory is not accurate. FIG. 5 shows an example calculated in detail by the inventor. This figure shows the relationship between the electron life, the radiation decay time τ4, and the electron energy under the conditions that the degree of vacuum in the storage ring is 10 −9 Torr and the storage current is 500 s^. Electronic energy is 200
When evaluating the lifetime of a single electron in a region near or below MeV, it is extremely important to take into account the expansion of a mass of electrons due to minute Ron scattering between electrons. In the example shown in Figure 5, the swelling of the electron mass is determined by detailed calculations, and then the probability that the electrons will be scattered at a large enough angle to collide with a wall is evaluated, and the electron life τ7 is calculated. is decided.

As can be seen from FIG. 5, it was found that there is a lifetime of 200 seconds even near 50 MeV, where the lifetime of one electron is the shortest. This is a matter that requires revision of conventional dogma. In other words, even if electrons of 20 MeV or less are incident, the lifetime of one incident electron is from a few minutes to several tens of thousands.
It is kept for minutes.

The present invention is based on this new knowledge.

In the synchrotron radiation device according to the present invention, a linear accelerator that accelerates electrons to 20 MeV or less is used as a pre-stage accelerator, or a linear accelerator that accelerates electrons to 60 to 14011 eV.

A microtron is used.

When electrons with an energy of 20 MeV or less are injected into the storage ring, large vibrations in the electron beam trajectory (
The time τ for the betatron oscillations to decay is the electron lifetime τ7
becomes longer. Therefore, 20 electrons are added to the front accelerator.
When using a linear accelerator that accelerates to MeV or less, electrons cannot be made to be incident multiple times. However, a linear accelerator can inject 500 electrons or more in one injection by providing an energy width compression device at the subsequent stage. Therefore, after injecting such a large current once, it is accelerated to the rated value of, for example, 800 MeV over a relatively long period of time, that is, about 1 minute, which is ample time until the electron life τT, and then the accumulation state, high-intensity synchrotron radiation output will be obtained.

On the other hand, when using a microtron that accelerates electrons to 60 to 140 IeV as a pre-stage accelerator, it is not possible to inject a large current in one injection due to the characteristics of the microtron, but as can be seen from Fig. 5, Since the electron lifetime τ↑ significantly exceeds the radiation decay time τ4, electrons can be injected multiple times after waiting for the betatron oscillation of the incident beam to decay. Therefore, in this case also 500s^
Or more electrons can be incident. and,
In this case as well, high-intensity synchrotron radiation output can be obtained by accelerating to the rated value of, for example, 800 MeV over a relatively long period of time, that is, about one minute, and then shifting to the storage state.

In this way, by using a linear accelerator that accelerates electrons to 20 Mev or less or a microtron that accelerates electrons to 60 to 1401 eV, a large current electron beam with the required energy can be delivered to the storage ring without rapid acceleration after injection. Can be accumulated.

Linear accelerators and microtrons with these characteristics are
Usually, it is small and contributes to suppressing the increase in size of the entire device. In addition, since electrons can be accelerated to the required energy without sudden acceleration after entering the storage ring, large eddy currents are not induced in the iron core that makes up the deflection electromagnet during acceleration. , the strength of the deflection magnetic field does not decrease. Therefore, the deflection angle per deflection electromagnet can be increased, which can also contribute to reducing the number of deflection electromagnets and shortening the circumference of the storage ring.

Furthermore, in the synchrotron radiation device according to the present invention, the widths of the magnetic pole part and the yoke part in the iron core of each deflecting electromagnet are set in the above relationship, so that the cross-sectional area of the magnetic flux path of the yoke part is equal to that of the magnetic pole part. It can be the same or even better. Therefore, even with a sector-type core configuration, it is possible to supply a magnetic field of about 1.5 T, which is usually considered the maximum effective magnetic field of the core material, on the electron orbit, and it is not subject to the demagnetization effect described above. Coupled with this, the deflection angle per deflection electromagnet can be further increased, and as a result, the number of deflection electromagnets and the circumference of the storage ring can be further reduced.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a synchrotron radiation apparatus according to an embodiment of the present invention.

In the figure, 1 indicates a linear accelerator as a pre-stage accelerator. This linear accelerator 1 is a small one that accelerates electrons to 20) lIev or less, in this example, 15 Me2.

The electron beam accelerated by the linear accelerator 1 is passed through an energy width compression device 2 using a set of electron meandering magnets and an acceleration cavity.
After passing through the injector 3, it is injected into a storage ring 4 which is under a vacuum condition of about 10-' Torr.

The inside of the storage ring 4 is formed by a circulating cavity.

In this example, the storage ring 4 is not a completely circular ring but is formed in the shape of a square frame. The four apexes are formed into arc shapes having a length of one-fourth of a circle with a predetermined radius of curvature. Near the four arc-shaped parts of the storage ring 4, the electrons traveling inside the storage ring 4 are
A deflection electromagnet 5 for deflecting the beam is disposed.

Each deflection electromagnet 5 includes an iron core 6 and a coil 7 wound around the iron core 6 and formed of a normal conducting coil or a superconducting coil. The iron core 6 is formed in a sector shape, and as shown in FIG. It is provided with a yoke part 10 that connects the magnetic pole parts 8 and 9 around the central axis of the electron orbit P, and is formed into a sector shape as a whole. As shown in FIG. 3, the width L1 of the yoke portion 10 in the direction orthogonal to the electron trajectory P is set larger than the width L2 of the magnetic pole portion 8 (9) in the direction orthogonal to the electron trajectory P. . That is, by setting the widths L2 and Ll in the above relationship, the yoke portion 1
The cross-sectional area of the magnetic flux path in the magnetic pole portions 8 and 9 is made to be equal to or larger than that in the magnetic pole portions 8 and 9.

A quadrupole magnet 1] is arranged near the straight part of the storage ring 4, and a high frequency acceleration cavity 1 is arranged at one place in the straight part.
2 is provided. On the wall of the arc-shaped part of the storage ring 4, located outside the electron orbit P, there is a beam line 13 for guiding the generated synchrotron radiation to a predetermined location.
passes through storage ring 4 and is connected in tangentially extending relationship.

Furthermore, on the outer periphery of the storage ring 4, a relatively thin lead plate or the like is formed at the position where the storage ring approaches the curved part from the straight part with reference to the traveling direction of the electrons, as shown in Fig. 4. A gamma ray shield 14 is attached. Furthermore, a gamma ray shield 15 formed of a relatively thin lead plate or the like is also provided on the extension line where the storage ring 4 approaches the curved part from the straight part.
is located. Note that 16 in FIG. 4 indicates the wall of the building.

In the synchrotron radiation device configured in this way, electrons are accelerated by 1.5 MeV in the linear accelerator 1. The energy width of this accelerated electron beam is typically 1% or more wide. If the electrons are allowed to enter the storage ring 4 as is, many electrons will collide with the walls of the storage ring 4, making it difficult to increase the storage current. Therefore,
In this embodiment, an electron beam having a wide energy width is first passed through an energy width compression device 2 to reduce its energy width, and then is made to enter a storage ring 4.

The electron beam incident on the storage ring 4 is deflected along the orbit by the magnetic field given by the deflection electromagnet 5, and is further accelerated to a higher energy in the high frequency acceleration cavity 12 and circulates. In this case, as shown in Figure 5, by effectively utilizing the sufficiently long electron lifetime τ↑, 2
The high frequency acceleration cavity 12 is controlled to accelerate at a relatively slow rate of change of about 0 MeV/sec. Then, synchrotron radiation emitted when the electron beam in the storage ring 4 is deflected by the magnetic field while being accelerated to a target energy is extracted via the beam line 13.

Note that when the electron beam circulates within the storage ring 4 as described above, some of the electrons collide with the walls forming the storage ring 4, and γ-rays are emitted as a result of this collision. A detailed analysis of this phenomenon revealed that the part where the electrons concentrate and collide is the wall located in the straight part of the storage ring 4, and the collision occurs at an angle of incidence of about ]° or less with respect to this wall. It turns out. Based on such analysis results, in this example, γ-ray shields 14 and 15 are arranged on the outer periphery of the linear portion of the storage ring 4 and on an extension of the linear portion.

In this way, in the above embodiment, one electron is
A linear accelerator 1 that accelerates to 5 MeV is used. Therefore, it is possible to reduce the size of the pre-stage accelerator, and it is possible to reduce the size of the entire device. Further, as described above, even in the case of low-energy electrons, the lifetime τT is sufficiently long, so there is no need to rapidly accelerate the electrons after they enter the storage ring 4. Therefore, a decrease in the magnetic field strength of the polarizing electromagnet 5 that occurs during rapid acceleration can also be prevented. As a result, the magnetic field can be used effectively,
Since the deflection angle can be increased, the number of deflection electromagnets 5 can be minimized and the circumference of the storage ring 4 can be shortened.
The entire device can be further downsized. Furthermore, the deflection electromagnet 5
Since the magnetic flux path cross-sectional area of the yoke part 10 of the iron core 6 incorporated in the iron core 6 is set to be equal to or larger than that of the magnetic pole part 8.9, the magnetic flux path on the electron trajectory P in the deflection part can be made with the maximum effective magnetic field of the iron core material. It is possible to supply a magnetic field of about 1.5 T, which is thought to be around 1.5 T. Therefore, it is possible to increase the supplied magnetic field to the upper limit determined by the core material by using a sector-type core that is advantageous for downsizing, and as a result, the deflection angle can be increased while the deflection electromagnet 5 is downsized. Therefore, the entire device can be further downsized.

Furthermore, by providing the gamma ray shielding bodies 14 and 15 at the positions shown in the embodiment, it is possible to effectively shield the parts where gamma rays are concentrated and generated, so that the shielding function required of the wall 16 of the building can be achieved. Overall, the costs required for buildings and gamma ray shielding can be significantly reduced.

Note that the present invention is not limited to the embodiments described above. That is, in the embodiment described above, a small linear accelerator that accelerates electrons to 20 HeV or less is used as the front-stage accelerator, but a microtron that accelerates electrons to 60 to 140 MeV may be used as the front-stage accelerator. Microtrons in the above range are relatively small and do not adversely affect miniaturization of the overall device. In the case of a microtron, the single injection current is small due to its characteristics, but in the energy range mentioned above, the electron lifetime τ7 is much longer than the radiation decay time τ, so multiple injections are possible as mentioned above. It is. Therefore, even if a microtron is used, a large current can be accumulated, and the same effects as in the embodiments described above can be obtained.

[Effects of the Invention] As described above, according to the present invention, high-intensity synchrotron radiation output can be obtained while reducing the overall size.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a synchrotron radiation device according to an embodiment of the present invention, FIG. 2 is a perspective view showing only one deflection electromagnet incorporated in the device, and FIG. A view cut along the A-A line in the figure and viewed in the direction of the arrow, No. 4
The figure is a diagram showing the length of the bent portion of the storage ring incorporated in the device, and FIG. 5 is a diagram showing an example of calculation on which the present invention is based. 1...Linear accelerator, 2...Energy width compression device, 4
... Storage ring, 5... Deflection 7 is magnet, 6... Iron core, 7... Coil, 8, 9... Magnetic pole part, 10... Yoke part, 12... High frequency acceleration cavity, 13...Beam line, 14.15...γ-ray shield, P electron orbit. Applicant's Representative Patent Attorney Takehiko Suzue Figure 4, Ward 2, Ward 3, Figure 5

Claims (3)

[Claims] (1) High-energy electrons accelerated by a pre-stage accelerator are made to enter a storage ring maintained in a vacuum state, and the incident electrons are deflected by a plurality of deflecting electromagnets provided along the storage ring and circulate around the storage ring. In the synchrotron radiation device which extracts the electromagnetic waves emitted during the deflection, the front stage accelerator is a linear accelerator that accelerates electrons to 20 MeV or less, or a linear accelerator that accelerates electrons to 60 to 140 MeV.
Each of the deflecting electromagnets has a pair of magnetic pole parts facing each other in a direction perpendicular to the plane of the electron orbit with the electron orbit in between, and a pair of magnetic pole parts facing each other in a direction perpendicular to the plane of the electron orbit. The iron core is provided with a yoke portion that connects to the yoke portion, the whole being formed in a fan shape, and a width of the yoke portion in a direction perpendicular to the electron trajectory is set to be larger than a width of the yoke portion in a direction perpendicular to the electron trajectory of the magnetic pole portion. A synchrotron radiation device characterized by: (2) The synchrotron radiation device according to claim 1, wherein an energy width compression device is provided downstream of the linear accelerator. (3) The synchrotron radiation device according to claim 1, wherein a gamma ray shield is provided on at least one of the outer periphery of the straight portion of the storage ring and an extension of the straight portion.