JPS60236499A - Accelerating tube for linear accelerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to an acceleration tube for a linear accelerator.

Linear accelerators, which accelerate charged particles through electric fields created by microwaves, must operate under ultrahigh vacuum conditions.

However, since the accelerator tube is formed of a large number of cavity resonators along the axial direction that communicate with each other in the tube in order to accelerate charged particles, and is long, it is necessary to exhaust the gas from both ends with a vacuum pump. The pressure in the center of the tube due to gas released from the inner wall of the accelerating tube is not as low as at both ends, and if there is a sudden release of gas from the tube wall, it takes a long time for the pressure inside the tube to decrease. .

The purpose of the present invention is to shorten the time required for the pressure inside the acceleration tube, which is based on the gas released from the inner wall of the acceleration tube, to drop to a value that allows beam acceleration operation, and to lower the pressure inside the acceleration tube during operation. A long acceleration tube consisting of a large number of cavity resonators connected in series is evacuated from its end using a vacuum bonder, and charged particles are exposed to an electric field generated by microwaves inside the acceleration tube under ultra-high vacuum. In a linear accelerator that accelerates areas, a plurality of elongated exhaust holes with a large aspect ratio are provided in the tube wall of each cavity resonator in an axially symmetrical manner, and exhaust air is added by an exhaust pipe that hugs the acceleration tube through the exhaust holes. It is characterized by what it did.

Embodiments of the present invention will be described below with reference to the drawings.

In the drawing, (1) is a long acceleration tube;
) has one hole (2
) is integrally formed with a plurality of cavities (4), and each cavity (4) acts as a resonator for microwaves introduced from appropriate locations to emit charged particles. It is designed to accelerate. (51 is the acceleration tube (
1) is an axially long exhaust hole in the pipe wall, and the exhaust hole (5)
For example, four are provided axially symmetrically. (6) is the exhaust hole (5
) is an exhaust pipe that is evacuated from a suitable location by a vacuum pump (not shown).

The width of the exhaust hole 151 rt in the circumferential direction of the tube is set to a size that does not adversely affect the axially symmetrical electromagnetic field caused by microwaves in the tube, and the length of the tube in the axial direction is equal to the number of holes (5). On a related note, the size was chosen so that the necessary gas exhaust performance could be obtained, and the size was chosen so that microwaves introduced from a suitable location were blocked from the outside.

Next, its operation will be explained.

The acceleration tube (1) is evacuated from both ends by a vacuum bonder (not shown), and at the same time is exhausted through an axially long exhaust hole (5) drilled along its axis via an exhaust pipe (6). As the gas is transmitted through the pipe, the center and both ends of the pipe are evacuated uniformly, resulting in a drop in pressure.Also, even if gas is suddenly released from the pipe wall for some reason and the pressure inside the pipe rises, it is quickly removed. The pressure decreases.

When a charged particle, such as an electron, enters this tube from a charged particle source (not shown), the electron moves along the axis (7) under ultra-high vacuum due to the axial electric field formed by the microwave placed inside the tube. Accelerates without any problem.

Since the length of the exhaust hole (5) in the circumferential direction of the tube is short, it has little effect on the axisymmetric electromagnetic field caused by microwaves, and since the length of the exhaust hole (5) in the axial direction of the tube is long, current flows in the circumferential direction of the tube. As a result, non-axisymmetric electromagnetic fields that can cause the beam to diverge from the tube axis are less likely to occur.

Therefore, the axially long exhaust hole 151 has a higher electron acceleration performance than a round hole whose circumferential length is equal to the length of the exhaust hole 151. An exhaust performance that is twice the circumferential length (r)/(circumferential length r/) can be obtained.

As described above, according to the present invention, the inside of a long acceleration tube consisting of a large number of cavity resonators is evacuated from its end with a vacuum pump, and charged particles are generated by an electric field generated by microwaves inside the acceleration tube under an ultrahigh-speed vacuum. In a linear accelerator that accelerates, by providing elongated exhaust holes in the axial direction in the tube wall of each cavity resonator in an axially symmetrical manner, it is possible to uniformly exhaust the center and ends of the acceleration tube. Therefore, the pressure due to the gas released from the inner wall of the accelerator tube can be reduced in a short time, and the device can be started operating. Furthermore, even if there is a sudden release of gas within the accelerator tube, the pressure can be quickly reduced.

At this time, since the electric field formed by the microwave is not deteriorated, there is an effect that acceleration of electrons is not hindered.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention, and FIG. 2 is a sectional view taken along line A--A in FIG. 1. (1)... Accelerating pipe C)... Hole (3)... Partition plate (4)... Cavity 151... Exhaust hole (61... Exhaust pipe (7)... Shaft patent Applicant: Japan Vacuum Technology Co., Ltd.

Claims (1)

[Claims] A linear accelerator in which a long acceleration tube consisting of a large number of cavity resonators connected in series is evacuated from the end with a vacuum pump, and charged particles are accelerated in the tube under ultra-high vacuum by an electric field created by microwaves. A plurality of elongated exhaust holes having a large aspect ratio in the axial direction are provided in the tube wall of each cavity resonator in an axially symmetrical manner, and exhaust air is added by an exhaust pipe that embraces the accelerator tube through the exhaust holes. Accelerator tube for linear accelerator.