JPS5842141A - Pierce type electron gun - Google Patents

Abstract

PURPOSE:To obtain a pierce type electron gun employing an immersed cathode having good electron beam focus characteristic, by reducing the differential thermal expansion between the cathode tube and the wenelt electrode thereby suppressing the variation of the perviance at the operation. CONSTITUTION:The impregnated type cathode 10 is constructed such that a porous tungsten ingot having the porosity of 20% is prepared then impregnated with the non-oxygen copper and worked to make the angle of 67.5 degree against the outermost shell of the electron beam 80 for the purpose to provide the wenelt electrode at a portion. Then it is jointed to the molybdenum supporting tube 20 through the brazing or welding. Thereafter a heater 30 is arranged in said tube 20 together with the mixture of the alumina powder and the organic binder and sintered 40. Then barium oxide, calcium oxide and aluminum oxide are placed on a concave electron radiating face 11 then solved and impregnated. Thereafter a film 12 composed of metal such as tungsten is formed through the fused injection coating method on the surface portion of such impregnated type cathode 10 which functions as the wenelt. Said tubular cathode is jointed to the support 100 through the metallic supports 50, 60 thus to complete the pierce type electron gun.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam tube, and more particularly to an improvement in a pierce-type electron gun using an immersion cathode.

Conventionally, there are several types of electron beam tubes, one of which is an electron beam tube that has an electron gun, a slow wave circuit, and a collector. There are pipes, fly irons, etc.

FIG. 1 is a cross-sectional view of an example of a conventional pierce-type electron gun using an impregnated cathode. A cathode l having a porous tungsten substrate impregnated with nipalium-calcium aluminum oxide is attached to a support cylinder 2 made of molybdenum by brazing or welding, and a sintered body 4 in which a heater 3 is attached is attached to the support cylinder 2 made of molybdenum by brazing or welding. The cathode tube is formed by being embedded in the tube.

The cathode 1 is heated to about 1050° C. by the heater 3 and thermoelectrons are emitted. The cathode tube is supported by a Wehnelt electrode 7 via metal supports 5 and 6 made of tantalum, covar, or the like. Incidentally, the gold-based support 5 is made of 1, for example, Tri 4?, in order to reduce the heater power. Tudo type (3 hanging structure)
etc. are used. Due to the focusing action of the Wehnelt electrode 7 having the same potential as the cathode 1, an electron beam 8 is formed and guided into a slow wave circuit (not shown) through a hole in the anode 9. Note that the Uenel F electrode 7 is at an angle of 67.5 degrees (
(referred to as the pierce angle). An electron gun with this configuration is called a pierce-type electron gun after the researcher. In such a piercing type electron gun, it is important for electron beam focusing to match the electrode spacing between the cathode 1 and Wehnelt electrode 7 and the electrode spacing between the cathode 1 and anode 9, that is, the perveance, to design values. In particular, it is important to achieve dimensional accuracy between the narrowly spaced cathode and Wehnelt.

However, in the conventional piercing type electron gun using an impregnated cathode, the operating temperature of the cathode 1 is about 10! The temperature of the entire cathode tube becomes high (So℃), whereas the Wehnelt electrode 7 only partially heats up to about 400'C1i degrees even under the influence of radiant heat and conduction heat from the cathode tube. There was a large temperature difference between the electrode and the Wehnelt electrode.This is due to the inherent coefficient of thermal expansion of the materials such as porous tungsten and linden that form the cathode tube, and the thermal expansion of the Wehnelt electrode, which is generally made of copper. Due to the difference in ratio, both electrodes undergo complicated dimensional changes during operation, and it is quite difficult to match the perveance to the design value.In particular, as shown enlarged in Figure 2, cathode 1 and Wehnelt electrode 70 interval d
If %B changes (if the cathode protrudes too far, if the cathode falls too low, the dotted line is the design position), the electrons emitted from the end of the cathode 1 form the outermost shell of the electron beam 8. Because of this relationship, the electron beam tends to collide with the anode 9 or the slow wave circuit (not shown), and the focusing effect of the Wehnelt electrode cannot be made effective, making it difficult to obtain good electron beam focusing characteristics. Furthermore, there were layers with large variations in beam focusing characteristics among electron tubes with the same specifications.

Therefore, the purpose of this invention is to reduce the difference in thermal expansion between the cathode cylinder and the Wehnelt electrode that form the pierced electron gun, suppress perveance changes during operation, and use an impregnated cathode that can obtain good electron beam focusing characteristics. The purpose of the present invention is to provide a piercing type electron gun.

The electron gun according to the present invention is characterized in that the cathode impregnated with oxides of barium, calcium, and aluminum and the Wehnelt electrode are integrally formed with a bolus tungsten base.

Next, an example will be described. , FIG. 3 shows an impregnated cathode 10 with Wehnelt according to the present invention, a support cylinder 20 made of Solipden, and an alumina sintered body 40.
The cathode tube of the heater 30 is shown embedded in the heater 30.

Impregnated cathodes are made using a similar process. first,
Tungsten powder with a particle size of about 5 tons is pressed and about 2
A porous tungsten ingot with a porosity of 20% is produced by sintering at 200°C. Then, it is impregnated with, for example, oxygen-free copper to improve machinability and processed into the Wehnelt cathode shape of the present invention. In order to make a part of this cathode 10as a Wehnelt electron, the electron beam 80 was designed using CAD.
It is machined so that it forms an angle of 67.5 degrees with the outermost shell. Copper is completely removed by vacuum treatment at 1800°C. Next, it is joined to the molybdenum reception cylinder 20 by attaching or welding. After that, a heater 30 made by winding a thin tungsten wire into a coil shape is placed in the molybdenum cylinder 20 together with a mixture of alumina powder and an organic binder, and heated to approximately 1700°C.
The kneaded material is sintered at 40°C. Next, a mixture of barium fermentation and calcium fermentation aluminum oxide in a molar ratio of (4:1:1) was placed on a concave sphere at an angle of 1°. Melt-impregnate at 1600'C. A coating 1 made of a metal such as tungsten is applied to the surface portion of the impregnated cathode 10 thus produced, which acts as a Wehnelt.
2 is formed by a melt spray coating method. This tungsten material is formed by burning and melting tungsten powder in a plasma spray gun and spraying it with compressed air. The thickness of this coating can be freely controlled, and in this case may be about 5 to 10 microns. This completes the cathode tube of the present invention. Next, this cathode tube is joined to a support 100 via a gold support 50.degree. 60 to complete a pierced electron gun.

The Wehnelt part of the impregnated @electrode made in this way is sealed by the tungsten coating and no monoatomic layer of barium is formed, so electrons are not emitted from this part and it functions well as a Wehnelt electrode. I can do it.

As described above, in the pierce-type electron gun having an impregnated negative electrode with Wehnelt according to the present invention, the cathode and the Wehnelt electrode part are integrally formed with a porous tungsten base. Argumentative as in
The Wehnelt voltage 11dd does not change. In other words, a good pierce-type electron gun can be obtained that allows the perveance to be adjusted to the design value, has a sufficient effect on the electrons emitted from the sardine part, and does not cause problems in electron beam focusing. can.

[Brief explanation of drawings]

Figures #/s1 and 2 are a sectional view and a partially enlarged view of a conventional piercing type electron gun using an impregnated cathode. 3rd wI is a cross-sectional view of a pierce-type electron gun in an embodiment of the present invention. l... Impregnated 1M cathode, 10... Impregnated cathode with Wehnelt electrode, 2.20... Molybdenum support cylinder, 3°30... Heater, 4.40... Alumina sintered body, 5
゜50... Tri-bod type metal JII [Support, 6.6
0... Gold j4III support, 7... Conventional Wehnelt electrode, 8°80... Electron beam, 9...° anode, 1
00... Metal support, 11... Electron emission surface, 12
...Tungsten coating.

Claims (2)

[Claims] (1) A pierce-type electron gun characterized in that a cathode impregnated with a barium-calcium-aluminum oxide and a Wehnelt electrode having an electron beam focusing function are integrally formed on a porous tungsten base. (2) The pierce-type electron gun according to claim 1, wherein a part of the porous tungsten base is coated with a metal film, and this part is used as a Wehnelt electrode.