JPH07211494A - Small electron gun - Google Patents

Abstract

PURPOSE:To provide a small electron gun that can be miniaturized. CONSTITUTION:A cathode 2 and an anode 3 are provided within a vacuum chamber 1 and an electron gun converges electrons passing through the anode 3. A yoke 18 made of soft iron and a converging magnet 20 comprising a permanet magnet 19 made of a rare earth-Co and enclosed in the yoke 18 are provided inside the vacuum chamber 1 on the emission side of the anode 3.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an industrial linac and X
The present invention relates to a small electron gun used for a line device.

[0002]

2. Description of the Related Art An electron gun used in an industrial linac system and an X-ray device used for nondestructive inspection has a cathode electrode, an anode electrode, a focusing electromagnet, etc. housed in a vacuum chamber and emitted from the cathode electrode to the anode electrode. The generated electrons are converged by a converging electromagnet to form an electron beam, which is accelerated to a predetermined energy by a high frequency accelerator and used.

[0003]

By the way, it is desirable that the electron gun is as small as possible, but if the focusing electromagnet is attached, there is a problem that the electron gun tends to increase in size.

Therefore, an object of the present invention is to solve the above problems and provide a small electron gun which can be made as small as possible.

[0005]

In order to achieve the above-mentioned object, the present invention provides an electron gun in which a cathode electrode and an anode electrode are provided in a vacuum chamber and electrons passing through the anode electrode are converged. In the vacuum chamber of, a yoke made of soft iron is provided and a focusing magnet accommodating a permanent magnet is provided in the yoke.
The permanent magnet contained in the yoke is made of rare earth-Co.

[0006]

According to the above construction, the focusing magnet can be made compact by using a permanent magnet made of rare earth-Co or the like without using an electromagnet as in the conventional case, and the focusing degree can be adjusted by making it replaceable.

[0007]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a vacuum chamber formed by porcelain stones 4 containing a cathode electrode 2 and an anode electrode 3, and an exhaust pipe 5 thereof is connected to a vacuum pump (not shown).

The cathode electrode 2 is a tubular Wenel electrode 6
The cathode terminals 8 and 9 are supported by an insulator 7 provided on the Wenel electrode 6. The Wenel electrode 6 is formed integrally with the flange 10 that holds the porcelain stone 4,
The electrons are held at the same potential as the cathode electrode 2, and the electrons emitted from the cathode electrode are converged by the action of the lines of electric force.

The anode electrode 3 is supported on the other end of the porcelain porcelain 4 so as to face the cathode electrode 2. An electron beam emission port 11 is formed in the exhaust chamber 1a on the emission side of the anode electrode 3 of the vacuum chamber 1, and a connection pipe 12 is formed in the emission port 11.
The high frequency accelerator 13 is connected via. A high frequency is introduced into the high frequency accelerator 13 from the waveguides 14 and 15, and the electron beam 17 is accelerated from the emission port 16 to, for example, 20 keV and emitted.

Now, the exhaust chamber 1a on the emission side of the anode electrode 3
A converging magnet 20 including a yoke 18 formed of soft iron in a hollow annular shape and a strong permanent magnet 19 such as rare earth-Co contained in the yoke 18 is replaceably provided.

In the above, the inside of the vacuum chamber 1 is set to 10 ⁻⁷ , 10 ⁻⁸ torr by the exhaust pipe 10. Cathode electrode 2
Electrons emitted from the anode 3 to the anode electrode 3 are focused on the focusing magnet 20.
It is converged by the magnetic force of the permanent magnet 19 and is supplied from the emission port 11 to the accelerator 13, where it is accelerated to a desired energy, and the beam 17 is emitted from the emission port 16.

The magnetic force of the permanent magnet 19 of the focusing magnet 20 is
Although it is constant, the potential applied between the cathode and the anode is constant, and if the central magnetic field is selected by changing the material and shape of the magnet in advance, no further adjustment is necessary.

[0014]

In summary, according to the present invention, it is possible to make the magnet compact by using a permanent magnet instead of an electromagnet as a converging magnet as in the conventional case, and to replace the magnet so that the degree of convergence can be adjusted.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 vacuum chamber 2 cathode electrode 3 anode electrode 18 yoke 19 permanent magnet 20 focusing magnet

Claims (2)

[Claims] 1. In an electron gun for providing a cathode electrode and an anode electrode in a vacuum chamber and focusing electrons passing through the anode electrode, a yoke made of soft iron is provided in the vacuum chamber on the emission side of the anode electrode. A compact electron gun having a focusing magnet in which a permanent magnet is housed in a yoke. 2. The small electron gun according to claim 1, wherein the permanent magnet housed in the yoke is made of rare earth-Co.