Indirect heating type electron source

Abstract

The utility model discloses an indirect heating type electron source which comprises a base, a heating assembly and an emitter. The heating assembly comprises a ceramic heating body, a conductive heating body and two conductive pins, the two conductive pins are fixed on the base and electrically connected with the conductive heating body, the conductive heating body wraps the outer wall of the ceramic heating body, and the ceramic heating body forms an embedding groove; the emitter is made of lanthanum hexaboride, and the emitter is embedded in the embedding groove. The utility model has the advantage of good reliability.

Description

Technical Field

[0001] The utility model relates to the field of electron sources, in particular to an indirect heating electron source. Background Art

[0002] In the field of electron sources, lanthanum hexaboride has a high melting point, good thermal stability and chemical stability, and it is not easy to form a contamination layer on the surface and has strong anti-poisoning performance; the electron work function of lanthanum hexaboride is 2.3eV~2.8eV, which is much smaller than tungsten (4.55eV). According to literature reports, the electron generation capacity of the electron source made of lanthanum hexaboride is 10 times that of tungsten filaments, and the life span is also 10 times that of tungsten filaments. Therefore, lanthanum hexaboride is an electron beam emission cathode material with excellent performance.

[0003] Due to the high electrical conductivity of lanthanum hexaboride, it is not suitable for making a self-heating cathode, so lanthanum hexaboride is generally used as an emitter (hereinafter referred to as lanthanum hexaboride emitter) and an additional heater is used to indirectly heat the lanthanum hexaboride emitter so that the emitter temperature reaches above 1500°C for use; at high temperatures, the boron atoms of lanthanum hexaboride will continue to diffuse into the metal, thereby destroying its own structure and affecting the emission performance and life. Therefore, pyrolytic graphite is generally used as a diffusion barrier and support for lanthanum hexaboride emitters, and tungsten wire is wound on the pyrolytic graphite as an emitter. It is also possible to directly design the pyrolytic graphite to serve as a heater while providing a barrier and support. However, pyrolytic graphite needs to ensure thermal stability and heat transfer capacity for lanthanum hexaboride emitters, and the matching gap between pyrolytic graphite and lanthanum hexaboride emitters needs to be strictly controlled. However, pyrolytic graphite is hard, brittle and easy to break, which makes the processing of pyrolytic graphite very difficult and costly. In addition, pyrolytic graphite is easily broken during transportation and use, resulting in damage. The above factors lead to the high cost and poor reliability of existing electron sources using lanthanum hexaboride emitters.

[0004] In view of the existence of the above problems, it is necessary to study an indirect thermal electron source, which has the advantage of good reliability in use. Utility Model Content

[0005] The utility model aims to provide an indirect heating electron source, which has the advantage of good reliability in use.

[0006] In order to achieve the above purpose, the solution of the utility model is:

[0007] An indirect heating electron source comprises a base, a heating component and an emitter; the heating component comprises a ceramic heating body, a conductive heating body and two conductive pins, the two conductive pins are fixed on the base and electrically connected to the conductive heating body, the conductive heating body covers the outer wall of the ceramic heating body, and the ceramic heating body forms an embedding groove; the emitter is made of lanthanum hexaboride, and the emitter is embedded in the embedding groove.

[0008] The gap between the emitter and the inner wall of the embedding groove is filled with graphite.

[0009] The emitter is provided with a conical discharge tip.

[0010] The indirect heating electron source further comprises a shielding ring made of a metal material matched with the ceramic heating body, the shielding ring surrounds the heating body and there is no contact between the shielding ring and the heating body.

[0011] The heating component also includes two conductive sheets, which are respectively connected to the two conductive pins, and the two conductive sheets are connected to the conductive heating body.

[0012] The conductive sheet and the conductive pin are made of metal, and the conductive sheet has a bend.

[0013] The conductive heating body is coated on the outer wall of the ceramic heating body.

[0014] The conductive heating body is made of tungsten.

[0015] The conductive heating body has a heating section in a square wave structure.

[0016] The heating component also includes a ceramic protector, which covers the ceramic heating body and the conductive heating body, and the conductive heating body is located between the ceramic protector and the ceramic heating body.

[0017] After adopting the above scheme, the utility model supports the emitter C through a ceramic heater. The ceramic heater is made of ceramic material, which makes the ceramic heater strong. In this way, the ceramic heater is not easy to be damaged and can effectively improve the reliability of the indirect heating electron source of the utility model. Moreover, the ceramic heater can also effectively prevent the boron atoms in the emitter from diffusing to the conductive heater, thereby ensuring the service life of the emitter. In addition, the ceramic heater is also easy to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the utility model.

[0019] Figure 2 It is a structural exploded view of the utility model.

[0020] Figure 3 The utility model is a cross-sectional view Figure 1 .

[0021] Figure 4 The utility model is a cross-sectional view Figure 2 .

[0022] Description of labels:

[0023] Base A,

[0024] Heating component B,

[0025] Ceramic heating body 1, embedding groove 11,

[0026] Conductive heating body 2, heating section 21, conductive connecting part 22,

[0027] Conductive pin 3,

[0028] Conductive sheet 4,

[0029] Emitter C, discharge tip C1,

[0030] Ceramic protector D,

[0031] Occlusion ring E. DETAILED DESCRIPTION

[0032] In order to further explain the technical solution of the present utility model, the present utility model is described in detail below through specific embodiments.

[0033] like Figures 1 to 4 As shown, the utility model discloses an indirect heating electron source, which includes a base A, a heating component B and an emitter C; wherein the base A can be made of ceramic; the heating component B includes a ceramic heating body 1, a conductive heating body 2 and two conductive pins 3, the two conductive pins 3 are fixed on the base A and electrically connected to the conductive heating body 2, the conductive heating body 2 covers the outer wall of the ceramic heating body 1, and the ceramic heating body 1 forms an embedding groove 11; the emitter C is made of lanthanum hexaboride, and the emitter C is embedded in the embedding groove 11.

[0034] When the indirect-heating electron source of the present invention is used, the heat-conducting heater is energized through the two conductive pins 3, so that the heat-conducting heater generates heat and heats the ceramic heater 1, and the ceramic heater 1 heats the emitter C after being heated; when the emitter C reaches a certain temperature, the emitter C emits electrons. Among them, the present invention supports the emitter C through the ceramic heater 1, and the ceramic heater 1 is made of ceramic material, so that the strength of the ceramic heater 1 is large, so that the ceramic heater 1 is not easy to be damaged and can effectively improve the reliability of the indirect-heating electron source of the present invention; and the ceramic heater 1 can also effectively prevent the boron atoms in the emitter C from diffusing to the conductive heater 2, thereby ensuring the service life of the emitter C; in addition, the ceramic heater 1 is also easy to process.

[0035] In an embodiment of the utility model, the gap between the emitter C and the inner wall of the embedding groove 11 can be filled with graphite, which can improve the heat conduction between the emitter C and the ceramic heating body 1, help reduce heat loss, and make the emitter C heat up faster.

[0036] In the embodiment of the present invention, the emitter C is provided with a conical discharge tip C1, which can increase the emission area of ​​the emitter C for emitting electrons.

[0037] In the embodiment of the utility model, the conductive heating body 2 can be directly coated on the outer wall of the ceramic heating body 1, so that the conductive heating body 2 can be closely combined with the ceramic heating body 1, so that the heat conduction between the conductive heating body 2 and the ceramic heating body 1 is better, which also helps to reduce the heat loss and make the emitter C heat up faster. The material of the conductive heating body 2 can be tungsten, which has a good heating effect; the conductive heating body 2 has a heating section 21, and the heating section 21 is a square wave structure, which can increase the effective length of the heating section 21, thereby improving the heating effect of the conductive heating body 2 on the ceramic heating body 1 and making the emitter C heat up faster.

[0038] In an embodiment of the utility model, the heating assembly B further comprises two conductive sheets 4, the two conductive sheets 4 are respectively connected to the two conductive pins 3, and the two conductive sheets 4 are connected to the conductive heating body 2; the conductive heating body 2 may be provided with two conductive connecting parts 22, the two conductive connecting parts 22 are respectively connected to the two conductive sheets 4, the conductive connecting parts 22 and the conductive sheets 4 may be connected by brazing or welding, the conductive sheets 4 and the conductive pins 3 may also be connected by brazing or welding, and the conductive pins 3 and the base A may be connected by bonding or brazing. The conductive sheet 4 has a bend so that the conductive sheet 4 can be elastic, so that the conductive sheet 4 can overcome the deformation caused by thermal expansion at high temperature, thereby increasing the structural thermal stability of the conductive sheet 4, and thus effectively improving the use reliability of the indirect heating electron source of the utility model. The conductive sheet 4 and the conductive pin 3 may be made of metal, so that the structural strength of the conductive sheet 4 and the conductive pin 3 is high, which also helps to improve the use reliability of the indirect heating electron source of the utility model.

[0039] In an embodiment of the utility model, the heating component B also includes a ceramic protector D, which covers the ceramic heating body 1 and the conductive heating body 2, and the conductive heating body 2 is located between the ceramic protector D and the ceramic heating body 1. The ceramic protector D can isolate the conductive heating body from the external environment, thereby reducing the volatilization of metal atoms of the conductive heating body at high temperature and reducing the corrosion of the conductive heating body by the external environment.

[0040] In the embodiment of the utility model, the indirect-heating electron source of the utility model further comprises a shielding ring E made of metal material matched with the ceramic heating body 1, the shielding ring E surrounds the heating body and the shielding ring E and the heating body are not in contact, and the shielding ring E can guide the electrons emitted by the emitter C, thereby increasing the density of emitted electrons. The shielding ring E can hold the ceramic protective body D and match the shielding ring E with the ceramic heating body 1, and the ceramic protective body D and the ceramic heating body 1 can be sintered and connected.

[0041] The above embodiments and drawings do not limit the product form and style of the present utility model. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present utility model.

Claims

1. An indirect thermal electron source, characterized in that: It includes a base, a heating assembly and an emitter; The heating assembly comprises a ceramic heating body, a conductive heating body and two conductive pins, wherein the two conductive pins are fixed on the base and electrically connected to the conductive heating body, the conductive heating body covers the outer wall of the ceramic heating body, and the ceramic heating body forms an embedded groove; The emitter is made of lanthanum hexaboride and is embedded in the embedding groove.

2. An indirect thermal electron source as claimed in claim 1, characterized in that: The gap between the emitter and the inner wall of the embedding groove is filled with graphite.

3. An indirect thermal electron source as claimed in claim 1, characterized in that: The emitter is provided with a conical discharge tip.

4. An indirect thermal electron source as claimed in claim 1 or 3, characterized in that: It also includes a shielding ring made of a metal material matched with the ceramic heating body. The shielding ring surrounds the heating body and there is no contact between the shielding ring and the heating body.

5. The indirect thermal electron source according to claim 1, characterized in that: The heating component also includes two conductive sheets, which are respectively connected to the two conductive pins, and the two conductive sheets are connected to the conductive heating body.

6. An indirect thermal electron source as claimed in claim 5, characterized in that: The conductive sheet and the conductive pin are made of metal, and the conductive sheet has a bend.

7. An indirect thermal electron source as claimed in claim 1, characterized in that: The conductive heating body is coated on the outer wall of the ceramic heating body.

8. An indirect thermal electron source as claimed in claim 1 or 7, characterized in that: The conductive heating body is made of tungsten.

9. An indirect thermal electron source as claimed in claim 1 or 7, characterized in that: The conductive heating body has a heating section in a square wave structure.

10. An indirect thermal electron source as claimed in claim 1 or 7, characterized in that: The heating component also includes a ceramic protector, which covers the ceramic heating body and the conductive heating body, and the conductive heating body is located between the ceramic protector and the ceramic heating body.

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