JPS6025840Y2 - linear accelerator - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a linear accelerator that uses a plurality of acceleration tubes in tandem.

First, a conventional linear acceleration tube will be explained with reference to FIGS. 1 to 5.

In FIG. 1 (aXb), electrons 1 generated by an electron gun (not shown) are accelerated by an accelerating electric field E generated inside an acceleration tube 4 by microwave power 3 supplied from a microwave source (not shown). Together with the electric field, it travels through the center of the high-vacuum accelerator tube 4 in the direction of arrow 2 and is accelerated.

6 is an accelerating disk having an inner diameter force hole 7 at the center for generating an accelerating electric field E. The accelerating electric field E is given by the following equation.

E = A/2rIP---(1) Formula % Formula %) () () P: Microwave power (MW) Here, the attenuation constant I and shunt impedance r are:
It is a function of the inner diameter of the accelerating disk 6, and in particular, 1 becomes a larger value as the inner diameter decreases.

Now, FIG. 2 shows the inner diameter of the acceleration disk 6 over the length of the conventional linear acceleration tube.

An accelerating tube with a constant inner diameter is used for M water.

In this case, the accelerating electric field E generated in the accelerating tube is caused by the loss of microwave power P3 in the accelerating tube, as shown in FIG.
As is clear from equation (1), it gradually decreases from the inlet to the outlet.

When the accelerating beam current 2 is increased in a device with an accelerating tube configured as described above, the beam blow-up phenomenon (hereinafter abbreviated as B-B-U phenomenon) occurs in which the beam breaks down above a certain current value. ) occurs.

There are two types of this BBU phenomenon:

(i) Oscillation type B-B-U... This occurs due to multiple repetitions of the same structure within one acceleration tube, and is likely to occur when the acceleration disc inner diameter nodule is constant.

(ii) Amplified type B-B-U...When multiple accelerator tubes are used in tandem, each accelerator tube acts like one cavity and causes B-B-U. The seeds of the HEM 11 electric field mode are gradually amplified, and the seeds grow longer, until the beam current 2 is missing in the later accelerating tube.

In the conventional example mentioned above, B・B−L of the above (I) and (II)
The J phenomenon is also likely to occur, and the performance of the electron accelerator is inferior.

Next, another conventional linear acceleration tube will be explained with reference to FIGS. 4 and 5.

In order to maintain the accelerating electric field E shown in FIG. 5 at a constant value over the length of the accelerating tube, the inner diameter of the accelerating disk is configured non-linearly, and in particular is configured to become rapidly smaller on the exit side.

Figure 4 shows this situation.

This example is a constant slope type acceleration tube, and the acceleration tube N of the same structure
The book consists of an electron accelerator.

In this case, there is an advantage that the above-mentioned oscillation type BBU is unlikely to occur, but there are the following disadvantages.

(i) The change in B2'' in the accelerating disk is non-linear,
In addition, since the change on the exit side is large, it is very difficult to machine the accelerating disk 6 and electrically adjust it after assembly, and it is difficult to design a common accelerating disk between each section. , it is also expensive.

(ii) Since a large number of accelerator tubes of the same structure are used, the amplified type B-B-U described above still occurs.

(iii) Since the inner diameter becomes very small on the exit side, the electron beam in the accelerating tube is likely to collide with the disk 6.

This idea was made in order to eliminate the drawbacks of the conventional linear accelerator tube as mentioned above.By simplifying the configuration of the accelerating disk, it is possible to achieve acceleration that is inexpensive and less likely to cause the B/B-U phenomenon. It provides a tube.

An embodiment of this invention will be described below with reference to the drawings.

FIG. 6 shows changes in the inner diameter of the accelerating disk in the longitudinal direction of the accelerating tube over the entire electron accelerator.

The entire acceleration tube is divided into two sections, and the first section I is the inner diameter of the acceleration disk 2a on the inlet side, as shown by the straight line 9.
It consists of one acceleration tube that changes linearly from t to the exit side acceleration disk 2a2.

The second section ■ has an inlet inner diameter of 2, as shown by the straight port.
It consists of Q acceleration tubes that vary linearly from as to inside the outlet u2a4.

The state of the accelerating electric field E at this time is shown in FIG.

This configuration provides the following advantages.

(i) Since the inner diameter of the accelerating disk is changed linearly over the length of the accelerating tube, machining of the accelerating disk 6 is facilitated, and a common accelerating disk 6 can be used for the first section and the second section. Since it can be designed to last a long time, it is inexpensive.

(ii) When capturing with one accelerating tube, the oscillation shape B-B
-U is unlikely to occur.

(iii) Since the entire accelerator tube is divided into two sections, amplified type BBU is also less likely to occur.

Particularly in this case, if 2a is set to >223, the effect is great.

Therefore, an accelerated beam with a large current can be obtained.

(iv) Since the inner diameter of the accelerating disk on the most exit side of the electron linear track can be set to a value that is not extremely small, the transmittance of the accelerated electron beam is improved.

In addition, in the above embodiment, the case where the entire accelerator tube is divided into two sections was explained, but when the entire accelerator tube is divided into three or more sections, the above-mentioned advantage (11) Amplification type B
It goes without saying that the effect on -B-U will be greater.

As described above, according to this invention, multiple types of acceleration tubes in which the inner diameter of the acceleration disk varies linearly within a predetermined range are connected in tandem, making machining of the acceleration disk easy. , and each acceleration tube can be designed to have a common acceleration disk.

As a result, manufacturing becomes easy and inexpensive.

It also has the advantage that beam blow-up phenomenon is less likely to occur.

[Brief explanation of drawings]

Figures 1a and b are longitudinal cross-sectional views and cross-sectional views taken along the line b-b to explain the principle and structure of a linear accelerator tube, and Figure 2 is a diagram showing the acceleration of a conventional linear accelerator tube for an electron accelerator with respect to its length. FIG. 3 is a characteristic diagram showing changes in the accelerating electric field. FIGS. 4 and 5 are characteristic diagrams explaining another conventional example. FIG. 6 is a characteristic diagram showing changes in the accelerating electric field. FIG. 7 is a characteristic diagram showing the change in the acceleration disk inner diameter node with respect to the acceleration tube length of the linear acceleration tube for a power accelerator according to an embodiment of the present invention, and FIG. 7 is a characteristic diagram showing the change in the accelerating electric field. In the figure, 1...electron, 2...acceleration beam current, 3...microwave power, 4...
Acceleration tube, 5... Curved acceleration electric field E, 6... Acceleration disk, 7... Hole in acceleration disk, 8... Inside 12
a, 9... 1st section characteristics, 1°...
...Inlet PIF, 2al, 11...Outlet inner diameter 2212.12...Second section characteristics, 13
...Oil inlet inner diameter 2a3.14...Outlet inner diameter 2a
4. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] It is constructed by connecting multiple accelerating tubes in tandem, each of which is formed so that the inner diameter of the accelerating disk that generates an accelerating electric field decreases linearly from the inlet side where electrons are received to the outlet side where electrons are emitted. A linear accelerator characterized in that the acceleration tubes connected in tandem in the linear accelerator include accelerating disks whose inner diameters vary linearly in different ranges.