JPH02201900A - Deflecting electromagnet for charged particle apparatus - Google Patents

Abstract

PURPOSE:To improve the uniformity of a magnetic field in the end part of a main coil by enlarging an end part of a main coil wound wire which forms a deflecting electromagnet, especially, the periphery area immediately above a balanced track and forming a straight line part in the perpendicular direction to a beam proceeding direction. CONSTITUTION:A deflecting electromagnet for a charged particle apparatus is comprised of an outside main coil wound wire 28, an inside main coil wound wire 29, an outside main coil terminal wound wire 30 which is projected to farther outside than the external radius R1 of the outside main coil wound wire, an inside main coil terminal wound wire 31 which is projected to farther inside than the internal radius R2 of the inside main coil wound wire, and a main coil end part wound wire 32 in a straight part connecting the terminal wound wires 30 and 31. To generate a uniform magnetic field in y-direction against x-direction in an area close to theta=90 deg., the wound wire may be infinite and parallel to the x-direction at theta=90 deg.. That is, theta=90 deg. and a straight line part as long as possible in the direction of the x-axis should be required. To satisfy that, the coil 31 and the coil 30 are projected to inside and outside, respectively, as mentioned above.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bending electromagnet for a charged particle device, and in particular,
The present invention relates to a deflecting electromagnet for a charged particle device that is equipped with means for improving the magnetic field uniformity of a magnetic field generated by a main coil.

[Prior art] Figure 3 shows, for example, the Japan Chemical Technology Information Center 1984
Yoghikaz Myahara, published in September.
u Miyahara), Corn Takata (Koj
1 Takata) and Tetsuya Nakanishi (Tetsu
Technical Report or l5SP by ya Naka-nfshi
) No. 21, “Superconducting Racetrack Electron Storage Ring and Coexisting Injector Microtron for Synchrotron Radiation”
Racetrack Electron Strag
e Ring and Coexis'tent Inj
ector Microzon for 5ynch
rotr-on←-circle→←Radiation) The conventional charged particle device described in J.
1) is a storage ring as a charged particle device that stores charged particles, and arrow (2) is an entrance beam line for guiding charged particles (for example, electrons) into the storage ring (1).

A superconducting bending electromagnet (3) is used to deflect charged particles to form a balanced orbit (4), and is made up of a combination of coils to 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 deflection electromagnet (3). This synchrotron radiation is Zincroto 07 synchrotron radiation or S
OR(Synchrotron 0rbitalRa
It is taken out to the outside and used for V graphics, etc. Generally, the synchrotron radiation beam line (5) is equipped with a bending electromagnet (
3), but here only one is shown for each bending electromagnet (3), and the others are omitted.

A quadrupole electromagnet (6) focuses the charged particles within the storage ring (1). The large pole electromagnet (7) corrects the nonlinear magnetic field or gromaticity of the bending electromagnet (3). The skin cavity (8) compensates for the energy loss of the charged particles due to the emission of synchrotron radiation and accelerates them to a predetermined energy. The kicker (9) is for assisting the incidence of charged particles by shifting the equilibrium trajectory (4) when the charged particles are incident from the incident beam line (2). The vacuum donut (lO) provides a path for charged particles. The inflector (11) is for making charged particles enter the storage ring (1) from the entrance beam line (2),
A vacuum pump (12) maintains a high vacuum inside the vacuum donut (10). Each of these parts is arranged along a balanced trajectory (4).

The vacuum donut (10) is made of a stainless steel material that has high mechanical strength and is easy to bake.
The inside of the chamber is maintained at an ultra-high vacuum by a vacuum pump (12) to prevent charged particles from colliding with gas molecules and losing energy and shortening their 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 eccentric main coils forming (1
3) is a Tonosho coil, and (14) is a T1 coil, which is shaped like a banana by bending a racetrack coil with a deflection curvature. Incidentally, since the upper T1 coils (13) and (14) have a high magnetomotive force, they have an air-core structure without using an iron core. Arrow m,, m, is up, T1 coil (13), (
14), and the arrow S indicates the traveling direction of the electron beam on the equilibrium orbit (4).

Furthermore, as is clear from FIGS. 5 and 6, the equilibrium orbit (4) has a radius ρ on the plane of polar coordinates Rθ (z = O).
. It is represented by a semicircle and straight lines connected to the front and back of this semicircle. ρ1. ρ is the T1 coil (13
), (14) are the inner radius and outer radius, respectively.

Moreover, the shaded part (27) is the upper end of the T1 coil.

(28) is the outer coil winding, and (29) is the inner coil winding.

Furthermore, Fig. 7 shows the main coil (3) and the main coil (3).
Quadrupole shim fill (15) that corrects the error magnetic field generated by
and the large pole shim coil (2o), (1B), (
17) is the upper coil winding of the quadrupole shim coil (15), (rg), and (19) is the lower coil winding.

(21) to (23) are upper coil windings of the large pole shim coil (20), and (24) to (26) are lower coil windings.

With the above configuration, the charged particles incident into the storage ring (1) from the entrance beam line (2) are deflected in a pulsed manner by the inflector (11), and the kicker (9)
), the trajectory is shifted. The charged-3 particle initially orbits on an orbit slightly deviated from the equilibrium orbit (4), and after several revolutions, it continues to orbit on the equilibrium orbit (4) in the direction of arrow A. This equilibrium trajectory (4) is determined by the arrangement of the bending electromagnet (3) and the quadrupole electromagnet (6).

Due to current in Nao, m+, m= direction, upper T1 coil (1
The main magnetic field generated in 3) and (14) is in the -z (-y) direction, and the current flowing in the equilibrium orbit (4) is in the opposite direction to the electron beam direction S. Therefore, the upper T1 coil (13
), (14) A charged particle, i.e., an electron beam, passing between them receives an electromagnetic force in the direction of -R due to Fleming's left-hand rule, which causes the radius ρ to increase. can be bent with a curvature of

The radius ρ of this equilibrium orbit (4). is given by the following equation 0.

ρ. = P/(e-By) ・・■ However, the momentum e of the P near M child is the magnetic field generated in the y-axis direction of the electron charge By upper and lower main fills (13) and (14). Here, the y-axis is an axis parallel to the Z axis regarding the equilibrium orbit (4), and the X axis is the radius R of polar coordinates regarding the equilibrium orbit (4).
The axis is in the same direction as .

On the other hand, the high frequency cavity (8) accelerates charged particles, and the large pole electromagnet (7) corrects the non-uniformity of the magnetic field in the radial direction of the bending electromagnet (3) and corrects chromaticity.

In this way, the charged particles orbiting along the equilibrium orbit (4) are
When deflected by the electric field of the bending electromagnet (3), the electromagnetic waves due to bremsstrahlung are converted into synchrotron radiation and are connected to the synchrotron radiation beam line (
5) is radiated tangentially to the equilibrium orbit (4).

By the way, since the electron beam undergoes betatron oscillation around the equilibrium 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 vibration around the central orbit is A uniform magnetic field distribution (good magnetic field region) of about 10 -4 to 10 -3 is required over a range of several cm or more.

Upper and lower stop coils (13) consisting of superconducting deflection main coils.

If the magnetic field distribution in (14) is non-uniform, the equilibrium trajectory (4) of the electron beam will deviate from the center of the upper and lower coils (13) and (t4), but if this deviation is greater than a predetermined value and uniform in the direction A magnetic field is required at each θ position.

Therefore, in order to obtain this uniform magnetic field distribution, the main coil (
A shim coil is used to correct error magnetic fields such as the primary component and secondary component of the magnetic field generated in 3). The quadrupole shim coil (15) in FIG. 7 generates a magnetic field in the Y-axis direction that increases in proportion to the first-order component as X (or R) increases,
do. The large pole shim coil (20) generates a magnetic field in the Y-axis direction that increases in proportion to the second-order component as X (or R) increases. By determining the output magnetic field of each shim coil (15) (2G), that is, the shim coil current value, so as to cancel out the primary and secondary components, which are the error magnetic field components generated by the main coil (3), a uniform magnetic field distribution can be achieved. It becomes possible to obtain.

East Figure 8 is a diagram in which the large shim coil (20) is incorporated into the main coil (3). By the way, assuming that the beam traveling direction is the S direction, the S direction distribution regarding θ of the second-order component on the balanced trajectory (4) of the main coil (3) and the large shim coil (20) shown in FIG. This is shown in Figures (a) and (b). In the example in this figure, at θ=0°, the main coil (3)
The current value of the large-pole shim coil (20) was determined so that the secondary components of the large-pole shim coil (20) were the same. Figure 9 (
As shown in a), the secondary component of the main coil (3) is θ=
It has a nearly constant value in the range from 0° to θ=01, but θ
Since the magnetic field created by the main coil end ((27) in the range of = θ1 to 90° is different from the magnetic field created by the main coil (3) in the range of θ・0° to θ shown in Figure 8, 1 The second-order component is no longer constant. In the example shown in FIG. 9(a), there is a large negative second-order component between θ=θ and 90°.

This can be thought of as follows. Figure 10 Ca”
) is the X-direction distribution of the y-direction magnetic field B) r at θ=O' y=o. The magnetic field distribution varies depending on the distance between the outer coil winding (28) and the inner coil winding (29), etc., but when the outer coil winding (28) and the inner coil winding (29) are relatively far from each other, Give an example. As X increases from X = 0, the magnetic field approaches the outer coil winding and increases;
At position XI between x and wa, the magnetic field decreases because the windings between x and wa create a magnetic field in the opposite direction.
If it becomes thicker than , the value of the magnetic field becomes negative. From the above, Figure 10 (a
), the second-order component near X=O has a positive value. On the other hand, Fig. 10(b) shows the By magnetic field distribution at θ = 90° y = o, and the magnetic field is almost at its maximum near x = Q, but as X increases, the current flowing in the winding between 0 and Since the current component in the y direction creates a magnetic field in the opposite direction, the magnetic field decreases.

Furthermore, when the value exceeds the 0 point, the By magnetic field becomes negative. Compared to the distance between X=O and point b, the distance between x=O and point 6 is shorter, and the first
As shown in Figure 0 (b), it becomes negative with a small X. In other words, as shown in Figure 10(b), when X=0, a large negative 2
It has the following components.

In addition, Fig. 9(b) shows the two-stroke component of the large pole shim coil (20), and the second-order component is almost constant in the range of θ=0° to θ1, but when θ=0° is exceeded, the second-order component starts to decrease, and since there is no shim coil near θ = 90°, 2
The next component becomes almost zero.

However, since the winding of the shim coil creates a magnetic field between opposite directions like the main coil, it has a slight negative component as shown in FIG. 9(b). From the above, if the current value of the large pole shim coil (20) is determined so as to cancel the second-order component at θ=0°, a large negative error second-order component will be generated near the end of the main coil, θ=90°. will occur.

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

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a deflecting electromagnet for a charged particle device that can generate a uniform magnetic field distribution at the end of a main coil.

[Means for Solving the Problems] The bending electromagnet for a charged particle device according to the present invention widens the main coil winding end, especially the vicinity directly above the equilibrium trajectory, and forms a straight line perpendicular to the beam traveling direction (S direction). A section has been established.

[Function] In this invention, the straight portion at the end of the main coil creates a uniform magnetic field in the X direction.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, (28) is the outer main coil winding, (29) is the inner main coil winding, (30) is the outer main coil end winding that protrudes outward from the outer main coil winding outer radius R, (3
1) The inner radius of the 17441 winding is R3.With the above configuration, in order to generate a uniform y-direction magnetic field with respect to the X-direction near θ=90", as shown in FIG. It suffices if the winding is infinite and parallel to the X axis. In other words, θ = 90°
, it is effective to provide as long a straight line section as possible parallel to the X axis. In order to provide a straight section as long as possible at the end of the main coil winding, as shown in Figure 1, the inner main fill end winding (
31) to the inside of the inner main coil winding inner radius R, and the outer main coil end winding (30) to the outside of the outer main coil outer radius R3.

Although the coil winding was not specified in the above embodiment, if the fill winding is made of HiTc wire, a strong magnetic field can be easily generated at the nitrogen temperature.

[Effects of the Invention] As described above, according to the present invention, since the main coil end is widened and a straight portion is provided at the end, the magnetic field uniformity at the main coil end is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a main part of an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of an infinite length winding parallel to the X axis of FIG. 1,
3 to 10 relate to the conventional technology, FIG. 3 is a schematic plan view of a charged particle device, FIGS. 4 to 6 are perspective views, plan views, and front views of the main coil, respectively, and FIG. 7 is a schematic plan view of a charged particle device. FIG. 8 is an exploded perspective view of the main coil and shim coil, FIG. 8 is an assembled plan view, and FIGS. 9 and 10 are magnetic field distribution characteristic diagrams. (3) Main coil, (4) Balanced orbit, (2g),
(29)...Outer and inner main coil windings, (30)
, (31) ... i end of outer and inner main coil winding, (32) ... linear coil winding, R, ... outer radius of outer main coil winding, R, ... inner radius of inner main coil winding . In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A charged particle comprising a pair of main coils that form a loop so that currents in opposite directions flow inside and outside along a balanced trajectory around which the charged particle circulates, and that are placed across the balanced trajectory. In a bending electromagnet for equipment, the end winding of the outer main coil projects outward from the outer radius of the outer main coil winding, and the end winding of the inner main coil projects outward from the inner radius of the inner main coil winding. By this, the main coil winding end is widened, and the outer main coil end winding and the inner main coil end winding are connected by a linear coil winding substantially perpendicular to the balanced trajectory. Features of a bending electromagnet for charged particle devices.