JPH03173033A - Cathode body structure for electron tube - Google Patents

Abstract

PURPOSE:To prevent the occurrence of contraction and cracks of sintered body in a soldering process by filling alumina powder which is relatively small in size with a narrow range of size distribution, into the insides of heaters and spaces among heater wires so as to be sintered, and concurrently filling alumina powder which is in a wide range of size distribution, into the spaces of the heaters so as to be sintered. CONSTITUTION:Alumina powder which is relatively small in size with a small range of size distribution, is filled in the insides of heaters 3 and spaces 5 among heater wires which are arranged within a cathode support cylinder 2, and alumina powder which is in a wide range of size distribution same as that of a former one, is filled in the other spaces 4, and the aforesaid alumina powder is sintered thereafter. By this constitution, sintered alumina is hardly contracted or cracked even if it is subjected to high temperature up to about 2000 deg.C after sintering, and the circumferential section of a cathode can thereby be soldered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is particularly applicable to traveling wave tubes that require high current density operation.
This invention relates to cathode assemblies for electron tubes such as talistrons and electron guns.

[Conventional technology]

In electron tube cathodes that require high current density operation, in order to increase the thermal conductivity from the heater to the cathode base metal and heat the cathode base metal efficiently, many of them have conventionally used a cathode base metal. A structure has been adopted in which alumina powder is filled and sintered together with a heater in a cathode support cylinder, and the heater is embedded within the sintered alumina.

FIG. 2 shows an example of a conventional cathode structure for an electron tube of this type.

In the figure, 1 is a cathode base metal impregnated with an electron radioactive substance, 2 is a cathode support cylinder, 3 is a heater, 3a is a heater leg,
4 is sintered alumina.

The sintered alumina 4 is obtained by filling the cathode support tube 2 together with the heater 3 with one type of alumina powder having a wide particle size distribution by a precipitation method using alcohol or an organic solvent, followed by drying and sintering.

Heat from the heater 3 is conducted through the sintered alumina layer 4, reaches the cathode base metal 1, heats the cathode base metal 1, and causes electrons to be emitted from the surface.

[Problem to be solved by the invention]

In recent years, the number of electron tubes that require high assembly precision has increased, and it has become necessary to assemble the area around the cathode by brazing, which has traditionally been done by welding.

In Reiko's case, the brazing temperature is 92000°C, so
Sintered alumina will be exposed to high temperatures above the sintering temperature.

With conventional sintered alumina made of one type of alumina powder with a relatively wide particle size distribution range, the sintered body shrinks even more in the brazing process after sintering, and the sintered body shrinks even more. Cracks, etc. may occur.

If the shrinkage of the sintered body becomes larger or a crank occurs, the heat of the heater will not be effectively transferred to the cathode base metal 1. Also, the temperature of the heater will rise above the design value, causing the heater to It has a short lifespan.

The present invention was made to solve the above problems.
An object of the present invention is to provide a cathode structure in which shrinkage and cranking of the sintered body, which affect thermal conductivity and the life of a heater, do not occur during a brazing process.

[Means to solve the problem]

In order to achieve the above object, the cathode assembly for an electron tube of the present invention has relatively small particles in the space between the heater wires and the space between the heaters arranged in the cathode support cylinder, and has a particle size distribution range wider than that of the conventional one. The space is filled with alumina powder with a narrow particle size distribution, and the other spaces are filled with alumina powder with a wide particle size distribution range, which is the same as conventional ones, and then sintered.

〔Example〕

FIG. 1 shows an embodiment of the invention.

In the figure, 1, 2, 3.3a, and 4 are the same as or equivalent to the same reference numerals in Figure 2, and 5 is alumina powder with a relatively small particle size and narrow particle size distribution range compared to sintered alumina 4. It is a sintered alumina made of

The cathode base metal work is fixed to the cathode support cylinder 2 with a high melting point brazing material, and the average particle size is 70 to 110μ inside the cathode support cylinder 2.
m powder (30% weight ratio) and the average particle size is 10-30μm
(70% weight ratio) and alumina powder mixed with the powder (70% weight ratio) is deposited by a precipitation method using alcohol or an organic solvent, etc., from the back surface of the cathode base metal 1 (bottom surface of the cathode support tube 2) by about 0.5 to 1 m.
The alumina powder is filled to a thickness of m, and then the heater 3 is placed on top of this alumina powder. At this time, at the same time, a cylinder is placed which is inscribed in the inner wall of the cathode support cylinder 2 and circumscribed to the heater 3.

The center of the heater 3 is determined by this cylinder.

With the above structure, an average particle size of 20 to 2
Alumina powder, which is a mixture of 5 μm powder (90% weight ratio) and powder with an average particle size of 10 μm (10% weight ratio), is filled by the same sedimentation method as above.

After drying, the cylinder was removed and the remaining space inside the cathode support cylinder 2 was filled with powder with an average particle size of 70 to 110 μm (30% weight ratio) and powder with an average particle size of 10 to 30 μm (70% weight ratio). Fill the mixed alumina powder using the same sedimentation method,
After drying, it was held at about 1900°C for 60 minutes in a reducing atmosphere to heat and sinter.

According to the above method, a strong alumina sintered body is obtained, and even if it is subsequently heated in a reducing atmosphere at approximately 2000°C for 5 minutes, there is almost no increase in shrinkage or occurrence of cranks. It's gone.

Therefore, when the sintered alumina layer is configured as described above, the peripheral portion of the cathode can be assembled by brazing, and an electron tube with high assembly accuracy can be obtained.

(Effects of the Invention) As explained above, according to the present invention, even when sintered alumina is heated to about 2000°C after sintering, shrinkage becomes large and cranks hardly occur. Finally, it becomes possible to braze the peripheral part of the cathode, which has the effect of making it possible to obtain an electron tube with high assembly accuracy.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an example of a conventional cathode structure for an electron tube of this type. DESCRIPTION OF SYMBOLS 1... Cathode base metal, 2... Cathode support tube, 3...
Heater, 3a... Heater leg, 4, 5... Sintered alumina. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A cathode base metal impregnated with an electron radioactive substance is fixed to a cathode support cylinder, a heater is placed in the cathode support cylinder, and alumina powder is filled and sintered, and the heater is made of sintered alumina powder. In the cathode structure for an electron tube embedded in the cathode structure, the inside of the heater disposed in the cathode support cylinder and the space between the heater wires are filled with alumina powder having a relatively small particle size and a narrow particle size distribution range; A cathode structure for an electron tube characterized in that the space outside the heater is filled with alumina powder having a wide particle size distribution range and sintered.