JPH074800Y2 - Electromagnetic pole structure of cyclotron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a magnetic pole structure of an electromagnet of a cyclotron dedicated to protons and deutrons.

(Prior Art) Generally, a small cyclotron has a longitudinal sectional view of FIG.
As shown in the cross-sectional view of the drawing, an acceleration space 1 is horizontally provided between the opposing magnetic poles of electromagnets composed of yokes 2 and 3 and exciting coils 4 and 5 which are vertically opposed to each other, and an ion source is provided at the center of the magnetic poles. 6 is provided. In the accelerating space 1, two sets of fan-shaped electrodes 7, 7 and 8, 8 of the same shape, which are vertically opposed to each other in a horizontal plane, are arranged symmetrically and horizontally with respect to the center point, respectively. A high-frequency voltage from an oscillator 9 having a frequency f is applied to each of them via an RF final amplifier 10 and a feeder 11.

The facing surfaces of the facing magnetic poles are generally shown in FIG.
As shown in the plan view of (a) and the AA cross-sectional view of (b), the whole is divided into even parts, and the valley parts (V) 17 and the hill parts (H) 18 are alternately arranged. And hill section 18
The structure is such that they face each other.

The acceleration space 1 is evacuated by vacuum pumps 23 and 24, and the exciting coils 4 and 5 are excited by a variable DC power supply 25.

The charged particles emitted from the ion source 6 in the cyclotron having such a structure are constrained by the magnetic field in the acceleration space 1 between the magnetic poles excited by the exciting coils 4 and 5, and are accelerated by the RF electric field by the electrodes 7 and 8. It makes a spiral motion, and finally the deflecting deflector 14 guides the charged particle beam 15 to the extraction port 16.

In this case, the velocity of the charged particle beam 15 can be appropriately selected by adjusting the frequency of the RF voltage applied to the electrodes 7 and 8 and the exciting current of the exciting coils 4 and 5 required in this case.

Furthermore, when accelerating particles with different masses, such as protons or dutrons, the strength of the magnetic field in the acceleration region must be increased as the energy of the particles to be accelerated increases. Moreover, the amount of increase depends on the type of particles.

Therefore, in order to properly use the particles having different masses, as shown in the development view of the outer periphery of the magnetic pole shown in FIG. 5 and the plan view of the magnetic pole surface shown in FIG. Circulation trimming coils (CTC) 19 are arranged concentrically on the surfaces of the magnetic poles facing each other, and the hill portion 18 is provided with a fine adjustment of the particle position as shown in the plan view of FIG. The spirally shaped harmonic trimming coil (HTC) 20 is provided separately,
The inside of each of these coils 19 and 20 (the facing magnetic pole side) is covered with a ground plate 22, and the inside hill portion is further covered.
Electrodes 7 or 8 for acceleration are provided at 18 positions.

In this way, the magnetic field strength of the duhtron was corrected by adjusting the current of the CTC 19 to obtain the theoretical magnetic field strength for the duhtron as shown in the characteristic curve diagram of the magnetic field strength between the magnetic poles shown in FIG. The magnetic field of Dutron is generated only by magnetic poles without using CTC.

Furthermore, the fine adjustment of the particle extraction position was performed by magnetic field correction by adjusting the current of the HTC 20 on the surface of the hill portion 18.

(Problems to be solved by the invention) As described above, since the CTC19 and the HTC20 are arranged in a superposed state on the surfaces of the magnetic poles facing each other, as shown in the development view of the magnetic pole outer circumference shown in FIG. The magnetic pole spacing must be increased by the amount of the double coil of CTC19 and HTC20, and the magnetic pole spacing must be increased to secure the necessary acceleration space 1 and the efficiency of the electromagnet becomes poor. .

For this reason, the electromagnet becomes large in size in order to obtain the required magnetic field strength, and the exciting current also becomes large, which hinders the miniaturization of the device.

An object of the present invention is to solve the above problems and provide a device that can be downsized.

(Means for Solving the Problem) In order to achieve the above-mentioned object, in the electromagnet of the cyclotron dedicated to protons and dutrons, the composite correction coil 21 is provided in the valley portions 17 of the surfaces of the magnetic poles facing each other, A correction coil is not provided in the hill portion 18, and the composite correction coil 21 connects the two first conductors 21-3 on the radius of the magnetic pole and the two first conductors 21-3. In addition, the magnetic pole structure of the electromagnet of the cyclotron is formed by a plurality of arc-shaped second conductors 21-4 having the center point of the magnetic pole as the center.

(Operation) As described above, the lead wire 21-1 of the composite correction coil 21 provided in the valley portion 17 is used as the + terminal of the excitation power source, and the lead wire 21-2 is
When the required direct current is supplied by connecting to the terminals, each composite correction coil 21 acts as one HTC 20, and the entire magnetic pole surface is provided in every other valley portion 17 on the magnetic pole surface. Since current is flowing in the same direction, CTC1
Acts as 9.

(Embodiment) FIG. 1 is a development view of the outer circumference of a magnetic pole in which the composite correction coil of the present invention is arranged between magnetic poles, and FIG. 2 is a plan view of the composite correction coil of the present invention.

As shown in the first drawing, the composite correction coil 21 is arranged only in the valley portion 17, and no correction coil is arranged in the hill portion 18. The surfaces of the composite correction coil 21 and the hill portion 18 are covered with a ground plate 22, and the inside (on the opposite magnetic pole side) is covered.
The acceleration electrode 7 or 8 is provided at the position of the hill portion 18. The composite correction coil 21 connects the two first conductors 21-3 and 21-3 on the radius of the magnetic pole to the two first conductors 21-3 as shown in the second illustration, and It is formed by a plurality of arc-shaped second conductors 21-4 centered on the center point of the magnetic pole, and the two first conductors 21-3 are provided with lead wires 21- on the outer peripheral side of the magnetic poles, respectively. 1, 21-2 are connected. The lead wire 21-1 is connected to the positive terminal of the power source (not shown), and 21-2 is connected to the negative terminal.

The pitch interval and the thickness of the arrangement of the second conductors 21-4 may be appropriately adjusted according to the required theoretical magnetic field strength.

Next, the operation of the magnetic pole structure of the present invention will be described.

As described above, the second conductor 21-4 of each composite correction coil 21 has a concentric circular arc shape, and therefore acts as a 1/2 turn coil and thus acts as an HTC 20. Further, the composite correction coil 21 is arranged in the valley portion 17 of the magnetic pole surface, and operates as one CTC 19 by causing the current direction of the second conductor 21-4 to flow in the direction of rotation with respect to the magnetic pole center. .

In this case, since the composite correction coil 21 covers the entire surface of the valley portion 17, it exhibits 100% of the effect as the HTC20.
As 9 is only half of the total magnetic pole surface in the part of the valley part 17, so it shows a 50% effect, but the conventional HTC20 and CTC19
There is almost no difference compared with the case where they are provided separately.

(Effect of the Invention) As described above, the conventional correction coil having a two-layer structure of HTC20 and CTC19 is a single-layer composite correction coil 21 having both functions, so that the structure is The gap between the magnetic poles can be made smaller by the simplification, and the efficiency as an electromagnet is increased. Along with this, the exciting current can also be reduced, so that the DC power supply can be downsized.

[Brief description of drawings]

FIG. 1 is a development view of the outer circumference of the magnetic pole in which the composite correction coil of the present invention is arranged on the magnetic pole surface, FIG. 2 is a plan view of the composite correction coil of the present invention, and FIG. 3 is the characteristic of the magnetic field strength between the magnetic poles. Fig. 4 is a curve diagram, Fig. 4 is an outline view of the facing surface of the magnetic pole, (a) is a plan view, (b) is a sectional view taken along the line AA, Fig. 5 is a development view of the outer circumference of a conventional magnetic pole, and Fig. 6 is a conventional plan view. Plane view of the pole face, Fig. 7 is HTC
FIG. 8 is a vertical sectional view of the compact cyclotron, and FIG. 9 is a horizontal sectional view of the same. 17: Valley part, 18: Hill part, 21: Composite correction coil, 21-3: First conductor, 21-4: Second conductor.

Claims (1)

[Scope of utility model registration request] 1. A cyclotron electromagnet dedicated to protons and deutrons, wherein a complex correction coil is provided in a valley portion on the surface of the opposing magnetic poles, and no correction coil is provided in a hill portion. The coil includes two first conductors on the radius of the magnetic pole surface, and a plurality of arc-shaped second conductors connecting the two first conductors and having the center point of the magnetic pole as the center. The magnetic pole structure of the electromagnet of the cyclotron characterized by being formed by.