JPH02201899A - Bending electromagnet for charged particle devices - Google Patents

Abstract

PURPOSE:To enlarge an output magnetic field of a coil and make a correction of an error magnetic field easy by dividing a main coil in up and down directions so as to make the open angle of one main coil closer to the balanced track plane smaller than that of the other, forming a black between the balanced track plane and the other main farther from the balanced track plane, and installing a shim coil for end part correction in the blank. CONSTITUTION:A deflecting magnet 3 is comprised of a balanced tracks 4, and one main coil wound wire 27, which is closer to the balanced track plane, of an upper main coil wound wire divided into two, the other main coil wound wire 28 which is father to the plane, as the same way, one main coil wound wire 29, which is closer to the balanced track plane, of a lower main coil wound wire divided into two, the other farther main coil wound wire 30, and a quardrupole shim coil 31 composed with coil wound wires 32-35 for end part correction. The open angle theta1 of the main coils 27, 29 is set to be small and the open angle theta2 of the main coils 28, 30 is set to be large. By this way, the end parts of the coil 27 and the coil 28 are dispersed effectively and the absolute value of a magnetic field strength which is in proportion to the strength of an error coil formed by end part wound wire is decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a deflection magnet for a charged particle device, and in particular to a deflection electromagnet for a charged particle device that is equipped with means for correcting an error magnetic field generated by a main coil. It is related to.

[Prior art] Figure 3 shows, for example, the Japan Chemical Technology Information Center 1984
Yoshikaz Myahara, published in September.
u Miyaharal, Koji Kukata
Takatal and Tetsuya Nakanishi
Technical Report of l5SPIN by Naka-nishi
o, 21. Super f! for r synchrotron radiation! 14
Racetrack Electron Storage Ring and Coexisting Injector Microtron (Superconducting®
acetrack Electron Strag
e Ring and Coexistent
Tnject, or Microtron for 5
The conventional charged particle device described in ynchrotron RadiaLionlJ is shown, and in the figure (1)
indicates a storage ring as a charged particle device that removes charged particles, and arrow (2) indicates a storage ring that stores charged particles (e.g. electrons).
1) An entrance beam line for guiding the beam into the center. A superconducting bending electromagnet (3) deflects charged particles into an equilibrium orbit (4).
), and consists of a combination of deflection coils, which will be described later.

The arrow (5) is a synchrotron radiation beam line for extracting the synchrotron radiation generated when charged particles are deflected by the recessed electromagnet (3). This synchrotron radiation is synchrotron radiation, or
OR(Synchrotron 0rbitalRad
It is called a synchrotron radiation beamline (IALion) and is taken out to the outside and used for
) is a bending electromagnet (3) in order to increase the utilization efficiency of the device.
There are many locations along the way.

Here, only one bending electromagnet (3) is shown, and the others are omitted.

The V3 pole'R magnet (6) focuses the charged particles in the storage ring (1). The Am electromagnet (7) corrects the nonlinear magnetic field or chromaticity of the bending electromagnet (3). The radio frequency cavity (8) compensates for the loss of the charged particles exposed to the emission of synchrotron radiation and accelerates them to a predetermined energy. Gicca (9) is for assisting the injection by shifting the equilibrium trajectory (4) when the beam is introduced from the r'R electron beam beam line (2). Vacuum donuts (10
) becomes a path for charged particles.

The inflector (11) is for injecting charged particles from the entrance beam line (2) into the storage ring (1), and the vacuum pump (12) is for injecting charged particles into the storage ring (1).
Maintain a high vacuum inside. Each of the above components is arranged along the equilibrium trajectory (4).

Note that the vacuum donut (10) has high mechanical strength.

In addition, it is made of stainless steel material that can be easily baked to prevent energy loss and shorten its lifespan.

Figures 4 to 8 show the above bending electromagnet (3), and the fourth
In the figure, (13) and (14) are bending electromagnets (3).
) is a pair of superconducting deflection main coils forming (1
3) is the Emperor coil, and (14) is the bottom stop coil, which is shaped like a banana by bending the racetrack coil with the deflection curvature. In addition, the upper and lower stop coils +131. (Since 141 has a high magnetomotive force, it has an air-core structure without using an iron core. Arrows m H and m z indicate upper and lower stop coils (131,
f14), the arrow S indicates the direction of the current flowing in each direction, and the arrow S indicates the equilibrium trajectory i! (4) Shows the traveling direction of the upper electron beam.

Furthermore, as is clear from FIGS. 5 and 6, the equilibrium orbit (4) is horizontal fiRθ (P with Z=01).

It is shown on a plane as a semicircle with a radius of - and a straight line leading to the front end of this semicircle. ρ1. ρtaki is a banana-shaped upper and lower stop coil f131. +141$ are the inner radius and outer radius, respectively.

Furthermore, FIG.
15), 6 (shows the shape of shim coil (2o), flG
1, H71 is the second side coil winding of the quadrupole shim coil (15), +181. +191 indicates the lower coil winding.

(21) to (23) are among the large shim coils (2o),
Upper coil winding, 1241 to (26) indicate lower coil winding.

FIG. 8 shows the main coil f131. It is a diagram in which a quadrupole shim coil (I5) is installed in +141. The Rokuyo shim coil has been omitted because it complicates the diagram. Figure 8 (1 shown in al.
13a+ indicates the end of the main coil winding behind the main coil winding.

With the above configuration, charged particles incident into the storage ring (1) from the entrance plane beam line (2) are deflected in a pulsed manner by the inflector (111) and are deflected in a pulsed manner by the inflector (111).
), the trajectory is shifted. Therefore, the 7-charged particle initially finds itself in an equilibrium orbit (4), which is determined by the arrangement of the bending magnet (3) and the quadrupole magnet (6).

Note that due to the current in the ml and m directions, the upper and lower stop coils f
131. The main magnetic field generated at +141 is -zf-y1
The current flowing in the equilibrium orbit (4) is in the opposite direction to the electron beam direction S. Therefore, the load M, that is, the electron beam, passing between 1, F, and the bottom coil f131. Can be bent. The radius - of this equilibrium orbit (4) is determined by the following equation 0.

P.

1=P/(e・By l ・・■ However, P・Electron motion Rei e: Electron charge By 2 Upper and lower main coils f131. +141 Generated magnetic field in the y-axis direction Here, the y-axis is the equilibrium It is an axis parallel to the Z axis regarding the orbit (4), and the X axis is an axis in the same direction as the radius R of the curved coordinate regarding the equilibrium orbit (4).

On the other hand, the high frequency cavity (8) accelerates charged particles.

The large pole@magnet (7) corrects the non-uniformity of the 1ifl field in the radial direction of the deflection tM1 stone (3) and corrects chromaticity.

In this way, the charged particles orbiting along the equilibrium orbit (4) are
When deflected by the magnetic field of the bending electromagnet (3), the electromagnetic waves due to bremsstrahlung radiation become synchrotron radiation, and the synchrotron beam line (5)
) in the tangential direction of the equilibrium trajectory (4).

By the way, since the electron beam is undergoing betatron oscillation around the planar orbit (4), generally speaking, in the direction perpendicular to the traveling direction S of the electron beam (mainly the R direction, that is, the X-axis direction), the oscillation around the central orbit is A uniform magnetic field distribution (good magnetic field region) of the order of io-' to lO is required over a range of 4 or more.It consists of the superconducting deflection main coil, and the magnetic field distribution of the bottom coil (3) and (3). is non-uniform, the equilibrium trajectory (4) of the electron beam is the upper and lower main coils (131, [
141, but this deviation is larger than a predetermined value (if this happens, the electron beam will hit the vacuum donut (10) and be lost. This uniform magnetic field distribution is It is also necessary.

Therefore, in order to obtain a uniform magnetic field distribution, a shim coil is used to correct error magnetic fields such as primary components and secondary components produced by the main coil. In FIG. 7, +151 is a quadrupole shim coil, which generates a magnetic field in the Y-axis direction that increases in proportion to the first-order component as X (or R) increases. +201 is the inner shim coil, and
] is generated in the Y-axis direction, which increases in proportion to the second-order component.

Figure 8 shows the main coil [131, port 4] and the quadrupole shim coil (
15), and in order to reduce the coil space, it is desirable to arrange the shim coil between the main coils, that is, in the area shown by diagonal lines in FIG. It is omitted in FIG. 8, and the coil f131. By determining the output Un field of each shim coil, that is, the shim coil current value, so as to cancel the generated primary and secondary components of +141, it becomes possible to obtain a uniform magnetic field distribution.

By the way, assuming that the traveling direction of the beam is the S direction, the main coil +1:11. +14) and the quadrupole shim coil (15), the S-direction distribution of the first-order component on parallel orbits is shown with respect to O in Fig. 9 fal fbl. In the example in this figure, the quadrupole shim coil (
15) was determined. As shown in the figure fat, θ
In the range of = 0° to θ = 01, the primary component of the main coil is almost a constant value, but in the range of θ = 01 to 90°,
The magnetic field created by the main coil 4 part (i3a) in Fig. 8 is shown in Fig. 8 i.
Since it is different from the magnetic field generated by the main coil in the range O=0° to θ1 shown in al, the first-order component is no longer constant. Figure 9 f
In the example of al, there is a large negative first-order component between θ=01 and 90', while in the S direction distribution of the quadrupole shim coil (+5) shown in Fig. 9fbl, there is a large negative first-order component between θ=0° and θ. Although it has a nearly constant first-order component over a range of 0201 or more, since the quadrupole shim coil (15) does not exist, the output magnetic field of the quadrupole shim coil (15), that is, the first-order component, becomes zero.

Therefore, in the range of θ=01 to 90°, the first-order component cannot be corrected at all, and a large error magnetic field still exists.

The inner shim coil can be considered in exactly the same way.

[Problem to be Solved by the Invention 1] Since the conventional bending electromagnet for a charged particle device is configured as described above, there has been a problem in that a large error magnetic field component is generated at the end of the main coil.

This invention has been made to solve the above-mentioned problems, and has the following objects: 1. To obtain a deflecting electromagnet for a charged particle device that can generate a uniform &a magnetic field distribution at the end of a main coil.

[Means for Solving the Problems] A bending electromagnet for a charged particle device according to the present invention divides the main coil winding in the vertical direction, and reduces the opening angle of the main coil close to the equilibrium orbital plane among the divided main coils. By increasing the opening angle of the main coil that is far from the balanced raceway surface, a space is created between the main coil that is far from the balanced raceway surface and the balanced raceway surface, and the end correction shim coil is installed in this space.

[Operation] In the present invention, error magnetic field components such as primary components and secondary components generated at the ends of the main coil are corrected by the end correction shim coil.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, (4) is the balanced orbit, +271 is the main coil winding that is closer to the balanced raceway plane among the two divided Emperor coil windings, (28) is the main coil winding that is far from the balanced raceway plane, (
29) is the main coil winding close to the balanced raceway plane among the T1 coil windings that are similarly divided into two.

(30) is the main coil winding far from the balanced raceway plane.

(31) is a four-pole shim coil for end correction, and the coil winding (
32) to (35).

In the above configuration, in order to reduce the error magnetic field component generated at the main coil end, the main coil end (February and T1 coil end 111S 1
It is effective to disperse the 281 windings. By dispersing the end windings, it is possible to reduce the absolute value of the magnetic field strength produced by the end windings (ie, this is proportional to the strength of the false MFa field). However, the range in which the error magnetic field occurs increases.

Specifically, as shown in Fig. 1, the main coil is divided vertically (in the example shown, it is divided into two parts), and the main coil 127) (291) close to the balanced orbital plane is made small in opening angle θ1, and the balanced orbit is This is possible by increasing the opening angle θ of the main coils +281 +301 that are far from the plane.The distribution of the first-order component S direction on the equilibrium trajectory (4) of this type of main coil is as shown in Figure 2 fal. .Comparing with the conventional linear component S direction distribution in Figure 9, it can be seen that the absolute value of the negative direction primary component between θ=θ and 90° has decreased.However, the range is By the way, in order to further reduce the primary component at the end of the main coil, a shim coil (quadrupole shim coil +311 for end correction in this example) is installed at the end to correct the error magnetic field at the end. It is necessary to obtain a large output magnetic field (large primary component) with a small number of ampere turns for this quadrupole shim coil for end correction, but this requires coil winding!11 +3
21 to (35) must be brought as close to the equilibrium orbital surface as possible. The main coil is placed closest to the balanced raceway to obtain a large magnetic field with a small ampere turn. However, in order to install a vacuum donut (10) etc. through which the beam passes, the first
There is an interval d shown in the figure. Shim coil winding is also used for end correction shim coils! ji +321 (33
) It is desirable to make the distance between the lower surface and the balanced raceway surface the minimum distance d, but in the past, it was not possible to install the lower surface of the shim coil windings (32) and (33) on the 8th surface because of the presence of the main coil end. . However, in this embodiment, the main coil is divided vertically, and the main coil (27
) (29) because the opening angle is small.

As you can see in No. 112(b), it is far from the flat orbital surface! A residual quantity is generated under the end of the main coil winding. A quadrupole shim coil (31) for edge correction is installed in this gap. ,t
In Fig. 52(b), the first-order component of the Vq pole comb coil θ=o'' is made equal to the first-order component of the main coil at θ=0°.
The S-direction distribution of the total output of the primary components of the quadrupole shim coil and the quadrupole shim coil for end correction when the current of the quadrupole shim coil is set to A is shown. In actual correction, a first-order component having a sign opposite to that of the first-order component shown in FIG. 2(b) is added to the main coil by turning the magnitude of the absolute straight position. The corrected first-order component is shown in Figure 2 ((:). @2 It can be seen that the first-order component has been corrected compared to Figure 2 (a).

In the above embodiment, the main coil is divided into two parts in the vertical direction, but the main coil may be divided into n parts, and the same effect can be obtained. Furthermore, in the above embodiments, the four-pole shim coil was used as an example, but a high-order shim coil such as a large-pole shim coil may be used, and similar effects can be obtained. Furthermore, in the above embodiment, it was stated that among the main coils divided in the vertical direction, the opening angle of the main coil that is closer to the balanced raceway surface is made smaller, but conversely, the opening angle of the main coil that is farther from the balanced raceway surface is made smaller. It is also possible to make it smaller. In this case, the end correction shim coil is placed on top of the main coil near the lower raceway surface. In this way, the output magnetic field of the end correction shim coil will decrease somewhat, but it is possible to obtain a uniform magnetic field. Further, although the coil wire material was not specified in the above embodiments, it is possible to easily obtain a bending electromagnet that can generate a strong magnetic field by using JTJ material.

[Effects of the Invention 1 As described below] 5 According to the present invention, the main coil is divided in the vertical direction, and among the divided main coils, the opening angle of the main coil near the equilibrium raceway surface is made smaller (by Since a space is provided between the main coil far from the balance raceway surface and the balance raceway surface, and the end correction shim coil is installed in this space, the output magnetic field of the end correction shim coil becomes large.1. The error magnetic field generated by the main coil at the end S can be easily corrected.

[Brief explanation of the drawing]

FIG. 1(a) is a partial plan view of an embodiment of the present invention, and FIGS. 1(b) and 1(c) are cross-sectional views taken along lines B-B and C-C in FIG. 1(a), respectively. , 213th? l is the first
FIG. 2 is a magnetic field distribution characteristic diagram of the one shown in FIG. Figures 3 to 9 relate to the conventional technology; Figure 3 is a schematic plan view of a charged particle device, Figure 4 is a perspective view of the main coil, and Figures 5 and 6 are similar to those in Figure 4. 7A is an exploded perspective view showing the main soil and shimcoil, FIG. 8 is an assembled plan view of the one shown in FIG. 7, and FIG. 9 is a magnetic field distribution characteristic diagram. (3)...Bending electromagnet, (4)...Equilibrium orbit,
(I5)...Shim coil, (27)(29)...
・Of the main coils divided in the vertical direction, the main coil closest to the balanced raceway surface, (28) (: 1 (1)... Among the main coils divided in the vertical direction, the main coil far from the balanced raceway surface ,
(311... Shim coil for end correction. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Shiga Dosho 4 Shiga all

Claims (1)

[Claims] 1 placed across the equilibrium orbit of charged particles
In a deflecting electromagnet for a charged particle device comprising a pair of upper and lower main coils and an end correction shim coil for correcting error magnetic field components generated by these main coils, the winding of the main coil is divided in the vertical direction, Among the divided main coils, the opening angle of the main coil close to the balanced raceway plane is made small, and the opening angle of the main coil far from the balanced raceway plane is made large, so that the main coil far from the balanced raceway plane and A deflecting electromagnet for a charged particle device, characterized in that a space is provided between the balanced orbital surfaces, and the end correction shim coil is disposed in the space.