JPH0470760B2 - - Google Patents

Description

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

Linear accelerators, which accelerate charged particles using 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 accelerator tube does not drop as low as at both ends, and when there is sudden gas release 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. Then, a long acceleration tube consisting of a large number of cavity resonators connected in series is evacuated from its end using a vacuum pump, and charged particles are accelerated in the acceleration tube under an ultra-high vacuum using an electric field created by microwaves. In a linear accelerator, 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 holds the acceleration tube through the exhaust holes. Features.

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

In the drawings, reference numeral 1 denotes a long acceleration tube, and the acceleration tube 1 is integrally formed with partition plates 3 having holes 2 in the center at predetermined intervals along the axial direction on the inner wall, thereby forming a plurality of cavities 4. Each cavity 4 acts as a resonator for microwaves introduced from appropriate locations to accelerate charged particles. Reference numeral 5 denotes an axially elongated exhaust hole in the tube wall of the acceleration tube 1, and for example, four exhaust holes 5 are provided axially symmetrically. Reference numeral 6 denotes an exhaust pipe which is connected to the exhaust hole 5 and is exhausted from a suitable position by a vacuum pump (not shown).

The exhaust holes 5 have a width in the circumferential direction of the tube such that it does not adversely affect the axially symmetric electromagnetic field due to microwaves in the tube, and the length in the axial direction of the tube is related to the number of holes 5, 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 would be blocked from the outside.

Next, its operation will be explained.

The acceleration tube 1 is evacuated from both ends by a vacuum pump (not shown), and at the same time is exhausted from an axially long exhaust hole 5 drilled along its axis via an exhaust pipe 6, so that the center of the tube The tube and both ends are uniformly evacuated and the pressure decreases, and even if the pressure inside the tube increases due to sudden gas release from the tube wall or the like for some reason, the pressure quickly decreases. Thus, when charged particles, such as electrons, enter the tube from a charged particle source (not shown), the electrons are moved along the axis 7 under ultra-high vacuum by the axial electric field formed by the microwave introduced into the tube. Accelerates without any problem.

Since the exhaust hole 5 has a short length in the circumferential direction of the pipe,
The microwave has little effect on the axially symmetrical electromagnetic field, and the length of the tube in the axial direction is long, so it acts to prevent the current from flowing in the circumferential direction of the tube, and as a result, the beam diverges from the tube axis. Non-axisymmetric electromagnetic fields that can cause problems are less likely to occur. Therefore, the axially long exhaust hole 5 has a higher electron acceleration performance than a round hole whose length in the circumferential direction is equal to that of the exhaust hole 5. Furthermore, compared to the round hole, an exhaust performance that is (axial length r of the exhaust hole 5)/(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 an accelerating linear accelerator, by axially symmetrically providing elongated exhaust holes in the tube wall of each cavity resonator, the center and ends of the acceleration tube can be uniformly exhausted. 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 the line A--A in FIG. 1... Accelerator tube, 2... Hole, 3... Partition plate, 4...
...Cavity, 5...Exhaust hole, 6...Exhaust pipe, 7...
shaft.

Claims (1)

[Claims] 1 A linear type 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. In the accelerator, 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 is added by an exhaust pipe that hugs the acceleration tube through the exhaust holes. Accelerator tube for linear accelerator.