JPS61133531A - Impregnated cathode - Google Patents

Abstract

PURPOSE:To obtain good emission life characteristic through preventing unnecessary thermal evaporation of electron radiating material from the faces except the electron radiating face of a cathode body by fixing wax material to the cathode body by means of laser weld after temporarily sintering it to the cathode body in the reducing atmosphere. CONSTITUTION:The wax material molten in trichlene is applied to the side face of a cathode body 1 by using a writing brush. Subsequently, temporary sintering of the wax material is finished by heating it to the temperature, 1,200 deg.C in the reducing atmosphere. Subsequently, a laser beam is radiated to the side face and back face of the cathoide body 1 the times respectively, a wax material film 11 is formed by fixing the wax material to the cathode body 1 and therefore, the impregnated cathode 20 is formed. Thereby, the thermal evaporation of the impregnated cathode 20 is caused from only the front of the cathode body 1 when the cathode is operated, resultautly the thermal evaporation amount of the electron radiating material can be reduced to about one third of the normal level.

Description

[Detailed description of the invention] Technical field of invention] The present invention relates to improvements in impregnated cathodes (1).

[Technical background of the invention and its problems]

An example of a conventional impregnated cathode structure will be explained using No. 31.

That is, an electron-emitting material consisting of a porous body CBaO, CaO, A7203, etc., obtained by compression molding tungsten (w) powder with a grain size of 3 to 10 μm and then sintering in a reducing atmosphere. The cathode substrate (1) obtained by melting and impregnating in an atmosphere is resistance welded into a cup (2) obtained by press-forming a tantalum plate with a thickness of 25 μm via a bonding material (4) to form an impregnated mold. It constitutes a cathode (10).

The dimensions of this cathode substrate (1) are, for example, outer diameter 1.5 and thickness 0.
．． It has 53 wings.

This impregnated cathode (l) is fitted into the top of the cathode sleeve (3) made by processing a tantalum plate with a wall thickness of 25 μm, and the cathode sleeve (3) is welded by laser light at the welding point (7).
The cup (2) and the cathode substrate (1) are welded.

The main purpose of using the cup (2) described above is to use the cathode substrate (1).
) from the cathode sleeve (3) due to thermal evaporation.
) This is to prevent attention to the heater (not shown) installed in the inside.

Near the bottom of the above-mentioned cathode sleeve (3) and with a wall thickness of 0,
Between the shoulders (61) of the cathode holder (6) manufactured by press-forming a Fe-Ni-Co alloy plate with a length of 25 m, there is a strap (made of tantalum ribbon with a wall thickness of Q, Q5 mm and a width of 0.7 s11). 5) is connected to the cathode sleeve (3) at the welding point (8), and the shoulder of the holder (6) is connected to the welding point (9).
) to complete the impregnated cathode structure.

However, in the case of the structure using the cup (2) described above, it is inevitable that there is a gap of about 0.01 mfi between the side surface of the cathode substrate (1) and the inner surface of the cup (2). Therefore, it is possible to prevent the electron emitting material from adhering to the heater, etc. in a direction other than the electron emitting surface, but the cup (2) cannot be used to prevent the ineffective evaporation of the electron emitting material from the sides and back surface of the cathode substrate (1). It's almost the same as the case. Furthermore, during resistance welding through the bonding material (4), the heat generated causes a considerable amount of electron emitting material in the cathode substrate (1) to ooze out, and in this respect, the electron emitting material is also ineffectively consumed. .

Furthermore, since the brazing temperature of the bonding material (4) is high, brazing must be performed before impregnating the electron emitting material. Taking the case of using Mo-Ru material as the bonding material (4), first, the temperature during brazing in a hydrogen furnace is quite high at approximately 2000°C, and this high temperature may cause undesirable damage to the porous body. Sintering and deformation will occur.

In addition, the recently developed 5C2 is said to have 2"L straight performance.
This method cannot be used for porous bodies that contain 0, and have a low cotton sintering temperature. Furthermore, the depth at which the bonding material (4) penetrates into the inside of the porous body is uneven, and in some cases, it may penetrate as deep as several tens of micrometers. Therefore, after brazing, the amount of electron emitting material that is impregnated with C2 is reduced, which also causes a shortening of the life of the impregnated cathode.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and provides an impregnated cathode that prevents unnecessary thermal evaporation of an electron emitting substance from a surface other than the electron emitting surface of a cathode substrate and has good emission life characteristics. It is intended to.

[Summary of the invention]

That is, the present invention provides a thermal evaporation prevention method capable of preventing thermal evaporation of the electron emitting material by covering the whole or part of the cathode substrate, which is formed by impregnating the electron emitting material into a porous body containing at least W, except for the electron emitting surface. In the impregnated cathode, the brazing material forming the heat evaporation preventing section or the brazing material and a member such as a high melting point metal foil are heated in a reducing atmosphere for about 12 hours.
It is an impregnated cathode characterized by being temporarily sintered on the cathode base at 00°C and then fixed to the cathode base by laser welding (two screws).

In other words, in the present invention, there is no need to raise the temperature of the cathode substrate to a high temperature range unlike in conventional brazing, and the intensity of the laser beam, the spot size, and (- means the position and number of welding points can be adjusted arbitrarily). This makes it possible to control the adhesion state of the heat evaporation prevention part.

[Embodiments of the invention]

Next, an impregnated cathode structure including an impregnated cathode of the present invention will be explained with reference to FIG.

That is, after compression molding tungsten particles having a grain size of 3 to 10 μm, BaO, CaO, AA! The cathode substrate m is melted and impregnated with a radioactive substance such as 203 in a high-temperature reducing atmosphere.
make. The dimensions of this cathode substrate (1) are, for example, an outer diameter of 1.5
M, thickness 0.5 mm.

Next, polystyrene and dioctyl phthalate are mixed with about 60% Mo - 40% Ru, melted with a brazing filler metal Wotriclean rolled up on a roll machine, and applied to the side surface of the cathode substrate (1) using a brush.

Temporary sintering of the brazing filler metal is completed by heating at 1200° C. for 5 minutes in a C2 reducing atmosphere. Since the bonding between the brazing material and the cathode substrate (1) is incomplete if this temporary sintering remains, a portion of the brazing material is then sintered and fixed to the cathode substrate (1) using a laser beam.

The laser used in this example is a pulse type YAG laser, with a pulse width of 2 m5ec and a repetition rate of L and a frequency of 10.
pps, energy 5 joules/pulse, beam diameter 0.7aφ, the back and side surfaces of the cathode substrate (1) are irradiated 7 times and 10 times to complete the adhesion of the brazing material to the cathode substrate (1) and form a brazing material film. A circle is formed to complete the impregnated cathode (20).

The oscillation conditions, optical system, etc. of this laser can be selected depending on the cathode substrate (10) produced and the brazing material C2 used.

This impregnated cathode (2) is a cathode sleeve (121) manufactured by processing a tantalum plate with a wall thickness of 25 μm, and is inserted into the top of the welding point (7).
3) The brazing material film OD and the cathode substrate (1) are welded.

This cathode sleeve (near the bottom of 3 mm and wall thickness 0.125 mm)
There is a wall thickness of 0.05ii between the shoulders of the cathode holder (6) manufactured by press-forming an Fe-N1-co alloy plate of n.
A strap (5) formed from a tantalum ribbon with a width of 0.7 mm is welded and fixed to the cathode sleeve at a welding point (8) and to the shoulder at a welding point (9) to complete an impregnated cathode structure.

The above-mentioned impregnated cathode f20) (for the second case, 1200
Since it can be temporarily sintered at a temperature much lower than that of the conventional method, such as 0.degree. C., it is also possible to braze the cathode substrate (1) impregnated with a seiton emissive material. It is also considered that thermal evaporation of the electron emitting material during cathode operation occurs only from the front surface of the cathode substrate (1). Therefore, compared to the conventional example, the thermal evaporation of the electron emitting material is reduced by about 1/3 (2).

As a result of actually testing the emission characteristics of the impregnated cathode of the embodiment and the conventional example, as shown in Fig. 2, in the C2 embodiment, the change in emission with respect to time is small (curve 01) (as shown in Fig. 2), but in the conventional example As shown in the song fJ +221, there was a large change in emissions from time C1 to time C2.

In this figure 2, the vertical axis is IIQQ 'Cb (br igb
Emissions without an electric field are taken at tnessTemperature), and the cathode loading is 1 A/d.

As can be seen from FIG. 2, the decay rate of emissions is less than half of that of the conventional example, and therefore it can be said that the impregnated type negative & of the embodiment has a life more than twice that of the conventional example.

In the above-mentioned embodiment, a brazing system was used to prevent thermal evaporation of the electron emitting material, but the present invention is not limited to this, and it is also possible to braze parts such as high-melting point metal foils or thin plates through a brazing material. is also possible.

Also, taking advantage of the lower sintering temperature compared to the conventional example, 5C2
Even if a porous body containing 03 is used, there is no deformation or shrinkage, and there is also the advantage that there is little penetration of the brazing filler metal. Furthermore, partial brazing C2 of the underground stone base can also be applied, and brazing has the advantage that the condition can be easily controlled.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an impregnated cathode with a long life and less thermal evaporation of the electron emitting material.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of an impregnated cathode structure equipped with an embodiment of the impregnated cathode of the present invention, FIG. 2 is a curve diagram comparing the emissions of the embodiment and a conventional example, and FIG. FIG. 3 is a partially cutaway perspective view of an impregnated cathode structure equipped with a conventional impregnated cathode. l... Cathode base 3... Cathode sleeve 5.
...Strap 6...Cathode holder 11...
・Brazing material film

Claims (1)

[Claims] Thermal evaporation of the electron emitting material is prevented by covering the whole or part of the cathode substrate except for the electron emitting surface, which is formed by impregnating an electron emitting material into a porous body obtained by sintering a powder containing at least W. In the impregnated cathode provided with a heat evaporation prevention section, the brazing material forming the heat evaporation prevention section or a member such as the brazing material and high melting point metal foil is fixed to the cathode base by laser welding. An impregnated cathode characterized by: