JPH04319298A - Deflection magnet for charged particle device - Google Patents

Abstract

PURPOSE:To provide a deflection magnet of a minimum heat intruding quantity in a simple support structure by minimizing electromagnetic force between coils and a return yoke. CONSTITUTION:There are provided a plurality of movable ferromagnetic shims 7 in a return yoke 11. The shims 7 are displaced by pushing screws 8, thus finely adjusting distances between the return yoke 11 and coils 2, 3. Consequently, it is possible to easily correct unbalance magnetic attraction force caused by an assembling error of the coils. Moreover, formation of a clearance 9 in the return yoke 11 can reduce outward leakage of a flux.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting deflection magnet for charged particles used in a synchrotron radiation generator or the like to bend the traveling direction of charged particles.

0002

[Prior Art] Figure 7 shows "Nakata et al. "Three-dimensional magnetic field analysis of superconducting 180° deflection magnet using vector potential method", Conference on Computation of Electron Magnetic Field, Computmag (September 1989), 321 page~
324 pages, (J. NAKATA et al., “THREE-DI
MENSIONAL MAGNETIC FIEL
D ANALYSYS OF SUPERCON
DUCTING 180°BENDING MAG
NETS BY POTENTIAL FEM
USING SUPER COMPUTERS”,C
ONFERENCE ON COMPUTATION
N OF ELECTOROMAGNETIC
FIELDS, COMPUMAG SEPTEMBE
3-7, 1989, TOKYO, JAPAN) is an exploded perspective view partially showing a cross section of a conventional superconducting deflection magnet. In the figure, coil 1 is
It consists of an outer diameter coil winding 2, an inner diameter coil winding 3, and a flip-up end coil winding 4 connecting these. 5 is a cryostat, 6 is a charged particle, 11 is a return yoke made of a ferromagnetic material such as iron, and 51 is a window through which the beam duct passes, and is configured symmetrically with respect to a plane 12.

Next, the operation will be explained. The charged particles 6 are subjected to a force in the radial direction mainly due to the vertical magnetic field (magnetic field interlinking with a pair of opposing coils 1) generated by the coil 1, and are deflected by 180°. At this time, the charged particles 6 generate synchrotron radiation in a direction perpendicular to the radial direction (tangential direction of the beam trajectory). A highly uniform and high magnetic field is required to bend a high-energy beam along a designed trajectory with a small radius. By connecting the ends of the coil 1 with the flip-up end coil winding 4, a highly uniform magnetic field can be obtained.

[0004] The cryostat 5 is a low temperature container for maintaining each coil 1 at an extremely low temperature. Cryostat 5
is usually made of a non-magnetic metal such as stainless steel in order to prevent low-temperature embrittlement and to avoid distorting the magnetic field generated from the coil 1. In addition, when a high magnetic field is generated, a large leakage magnetic field is generated in the surrounding area, which affects peripheral devices.
The return yoke 11 using ferromagnetic material
shield.

The return yoke 11 includes an inner return yoke 11a provided with a window 51 through which the charged particles 6 pass through a high vacuum beam duct, and an outer return yoke 11.
b, consists of upper and lower top plates 11c. When a high magnetic field occurs, each coil winding 2, 3, 4 and each return yoke 11
A strong electromagnetic force in a complicated direction is generated between a, 11b, and 11c.

[0006]

[Problems to be Solved by the Invention] Conventional deflection magnets for charged particle devices are constructed as described above, so it is impossible to adjust the distance between the coil winding and the return yoke. The electromagnetic force that acts between the top and bottom, the electromagnetic force that occurs between the inner diameter side coil winding, the end coil winding, and the inner diameter return yoke, and the part of the outer diameter of the outer diameter side coil winding and the end coil winding. It is difficult to balance the electromagnetic force generated between the side return yoke and the outer diameter side return yoke, and a strong electromagnetic force acts between the return yoke and the coil, and errors in assembling the coil may cause damage between the upper and lower coil windings or between the coil windings. There were problems such as an unbalanced magnetic attraction force occurring between the yoke and the return yoke. This required a support material to support the strong electromagnetic force, which complicated the structure of the deflection magnet, resulting in problems such as increased overall weight and increased consumption of cryogens such as liquid helium.

Furthermore, when a high magnetic field exceeding 2T is generated, the return yoke made of ferromagnetic material undergoes magnetic saturation and its magnetic permeability decreases, which deteriorates the shielding effect of the leakage magnetic field and prevents it from leaking to the outside. The leakage magnetic field increases and has a negative effect on charged particles. As a result, the amount of ferromagnetic material used to shield leakage magnetic fields increases, which increases the total weight of the deflection magnet, making it difficult to disassemble and transport, and increasing costs.

[0008] This invention was made in order to solve the above-mentioned problems, and the electromagnetic force acting between the end coil winding and the upper and lower ceilings, the inner diameter coil, and the inner diameter return yoke between the end coil and the inner diameter return yoke. This makes it possible to balance the electromagnetic force generated between the partial end coil winding, the outer diameter side coil winding, and the side return yoke, thereby reducing the radial electromagnetic force applied to the entire coil. The object of the present invention is to obtain a deflection magnet for a charged particle device that does not work substantially and can adjust installation errors between the coil winding and the return yoke due to errors during coil assembly or manufacturing errors.

Another object of the present invention is to obtain a deflection magnet for a charged particle device that can prevent a reduction in the shielding effect of leakage magnetic fields due to magnetic saturation of a ferromagnetic material and reduce leakage magnetic fields to the outside of the deflection magnet.

0010

[Means for Solving the Problems] A deflection magnet for a charged particle device according to the present invention includes a plurality of movable ferromagnetic shims provided on a return yoke installed at a certain distance from a coil winding. be.

[0011] Furthermore, a gap is provided in the return yoke installed at a certain distance from the coil winding, and the return yoke on the inside of the deflection magnet is made thicker than the return yoke on the outside across the gap. It is something.

0012

[Function] In this invention, by providing a shim to enable adjustment of the distance between the coil winding and the return yoke, the electromagnetic force acting between the end coil winding and the upper and lower return yokes can be reduced. The electromagnetic force generated between the wire, the end coil winding, and the inner diameter return yoke is balanced with the electromagnetic force generated between the partial end coil winding, the outer diameter coil, and the outer diameter return yoke, and the No radial electromagnetic force acts between the entire coil and the return yoke, and the supporting material that supports the electromagnetic force can be reduced. Furthermore, by providing a movable ferromagnetic shim, correction of coil assembly errors can be simplified.

Furthermore, by providing a gap between the return yokes, it is possible to prevent an increase in leakage magnetic field due to magnetic saturation of the ferromagnetic material, and to reduce the leakage magnetic field without increasing the weight of the ferromagnetic material.

[0014]

【Example】

Embodiment 1 FIGS. 1 and 2 show an embodiment of the present invention. In the figures, ρ is the radius of curvature of the charged particle, o is the center of curvature, 7 is a movable ferromagnetic shim, and 8 is the movable shim 7. This is a set screw for 9 is a void. In addition, the same reference numerals as in FIG. 7 indicate the same or corresponding parts.

The operation will be explained below. When the coil 1 is energized, a magnetic field is generated in the magnet. This magnetic field causes
Charged particles are subject to Lorentz forces. Using this Lorentz force, charged particles 6 incident from the incident beam line
bend. At this time, synchrotron radiation is generated in the tangential direction of the beam trajectory. When a magnetic field is generated, an electromagnetic force is generated that draws each coil winding 2, 3, 4 toward the return yoke 11. Since the return yoke 11 is installed so as to surround the winding of the coil 1, electromagnetic force is generated in complicated directions. By combining these forces, the entire coil 1 and the return yoke 1
A strong radial electromagnetic force acts between the two. In this embodiment, a ferromagnetic shim 7 that can be moved to the outside of the deflection magnet is provided on the upper and lower return yoke top plates 11c. By installing such a return yoke 11,
The distance between the coil winding 1 and the upper and lower top plates 11c can be equivalently increased, and the electromagnetic force acting between the coil 1 and the return yoke 11 changes. Therefore, by balancing these electromagnetic forces, the radial electromagnetic force acting on the entire coil can be made substantially zero.

[0016] Also, the coil 1 due to the assembly error of the coil 1
It becomes possible to adjust the distance between the return yoke 11 and the return yoke 11, and it becomes possible to correct the unbalanced magnetic attraction force based on this error. As a result, the electromagnetic force in the radial direction only responds to small eccentricities such as positional deviations during magnet excitation, so the support material to be supported can be made extremely small. This dramatically reduces the consumption of cryogens such as liquid helium, making the operating costs of the magnet extremely low.

Furthermore, when a high magnetic field is generated, the return yoke 11 made of a ferromagnetic material undergoes magnetic saturation. As a result, the shielding effect of the leakage magnetic field decreases, and the leakage magnetic field to the outside of the deflection magnet increases, and in order to effectively shield it, it is necessary to increase the amount of ferromagnetic material, which increases the weight. However, in this embodiment, since the air gap 9 is provided in the return yoke, the magnetic resistance becomes high once at the air gap 9. Therefore, the magnetic field penetrating the outer return yoke W2 across the air gap 9 is reduced, the magnetic saturation of the return yoke W2 is alleviated, and leakage magnetic fields can be effectively shielded without increasing the amount of the return yoke 11. especially,
By increasing the thickness of the inner return yoke W1 across the air gap 9, the magnetic field penetrating the outer return yoke W2 can be more effectively reduced.

Embodiments 2 to 4 FIGS. 3, 4 and 5 each show other embodiments in which ferromagnetic shims 7 having different movable directions are attached. Shown in FIG. 3 is a movable ferromagnetic shim 7 operating inside the deflection magnet. Figure 4 is Figure 1, respectively.
FIG. 2 shows a combination of movable ferromagnetic shims 7 that operate in different directions, and FIG. 5 shows a movable ferromagnetic shim that can move both inward and outward directions of the magnet.

Furthermore, although the shims 7 are attached to the upper and lower top plates 11c of the return yoke in each case shown in FIGS. 3, 4, and 5, they may be installed on the outer return yoke 11b or the inner return yoke 11a. By installing and using them in combination, adjustment in all directions is possible. Of course, it goes without saying that the same effects as in the above embodiment can be achieved.

Embodiment 6 FIG. 6 shows another embodiment of the second invention, in which gaps 9 are provided in the upper and lower return yoke top plates 11c. Also,
The air gap 9 can be installed in the inner return yoke 11a, or can be installed in a plurality of locations depending on the position and degree of magnetic saturation of the return yoke 11. It goes without saying that the same effects as in the above embodiment can be achieved.

[0021] Also, since the first invention and the second invention of this invention each have their own effects, the effect remains the same even when used alone, and of course, by combining both, the two effects can be obtained at the same time. Can be done.

Furthermore, the coil 1 can be either superconducting or normal conducting. Further, although the above embodiment shows a case where the deflection angle is 180 degrees, it can also be applied to other angles.

[0023]

[Effects of the Invention] As described above, according to the present invention, by attaching a plurality of movable ferromagnetic shims to the return yoke, it is possible to adjust the distance between each coil winding and each return yoke. , it is easy to balance the electromagnetic force acting between each coil winding and each return yoke, and the radial electromagnetic force acting between the coil and return yoke can be made substantially zero. Furthermore, assembly errors in the coil winding can be easily adjusted from the outside. Therefore, the number of supporting materials can be reduced, the construction of the device can be facilitated, the device can have high performance, and operating costs can be reduced.

Furthermore, by providing a gap in the return yoke, it is possible to reduce the leakage magnetic field to the outside of the magnet without increasing the weight of the return yoke, preventing the weight of the magnet from increasing, and preventing the movement of the deflection magnet and the surrounding equipment. This has the effect of simplifying shielding.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of any one of claims 1, 2, and 3 of the present invention.

FIG. 2 is a plan sectional view of that of FIG. 1;

FIG. 3 is a cross-sectional view of another embodiment of claim 1 of the present invention.

FIG. 4 is a cross-sectional view of still another embodiment of claim 1 of the present invention.

FIG. 5 is a cross-sectional view of another embodiment of claim 1 of the present invention.

FIG. 6 is a cross-sectional view of another embodiment of claim 2 or 3 of the present invention.

FIG. 7 is a partially sectional exploded perspective view of a conventional deflection magnet for a charged particle device.

[Explanation of symbols]

1 Coil 2　　　Outer diameter side coil winding 3 Inner diameter side coil winding 4 End coil winding 6 Charged particles 7 Ferromagnetic shim 9 Void 11 Return yoke

Claims (3)

[Claims] 1. A pair of coils consisting of an outer diameter coil winding, an inner diameter coil winding, and an end coil winding connecting these coil windings, and a return that surrounds the coil at a certain distance. A deflection magnet for a charged particle device, characterized in that the deflection magnet for a charged particle device is equipped with the above return yoke provided with a plurality of movable ferromagnetic shims. 2. A pair of coils consisting of an outer diameter coil winding, an inner diameter coil winding, and an end coil winding connecting these coil windings, and a return that surrounds the coil at a certain distance. A deflection magnet for a charged particle device, characterized in that the deflection magnet for a charged particle device is equipped with the above-mentioned return yoke in which a gap is formed to reduce a leakage magnetic field to the outside of the magnet. 3. The deflection magnet for a charged particle device according to claim 2, wherein the return yoke inside the magnet is thicker than the return yoke outside the magnet across a gap.