Vacuum insulation displacement small-diameter high-voltage vacuum device

Abstract

The utility model discloses a vacuum insulation displacement small-diameter high-voltage vacuum device, which comprises a shell, a high-voltage electrode and a ground electrode, the high-voltage electrode and the ground electrode are arranged in the shell, a special-shaped ceramic tube is arranged between the high-voltage electrode and the grounded shell, and the special-shaped ceramic tube comprises an insulation displacement area and a surface insulation area. Conductive layers are arranged on the inner wall and the outer wall of the ceramic tube in the insulation displacement area, the conductive layer on the outer wall is connected with the shell, the conductive layer on the inner wall is connected with the high-voltage electrode, one end of the ceramic tube in the creeping insulation area is connected with the ceramic tube in the insulation displacement area, and the other end axially extends towards one side of the ground electrode. According to the utility model, a main electric field is transferred from a vacuum gap to a ceramic component body, a high electric field established in vacuum by an external potential boundary is eliminated, and a ceramic body breakdown with a higher and more stable threshold value is adopted to replace a vacuum gap breakdown with a lower and unstable threshold value; and meanwhile, the surface insulation position of the ceramic is transferred to a low electric field region for surface breakdown isolation, so that the surface breakdown probability is greatly reduced.

Description

Technical Field

[0001] The utility model belongs to the field of high-end equipment, and specifically relates to a small-diameter high-voltage vacuum device with higher insulation performance than traditional vacuum electrode gap breakdown. Background Art

[0002] Vacuum electronic devices refer to devices that convert one form of electromagnetic energy into another form of electromagnetic energy by means of the interaction between electrons and electromagnetic fields in a vacuum or gas. They have a vacuum-sealed tube shell and several electrodes. The tube is evacuated to a vacuum with a residual gas pressure of 1E-4 to 1E-8 Pa. High-voltage vacuum devices are vacuum electronic devices that use high-voltage physical processes, such as high-voltage vacuum switches and circuit breakers.

[0003] Among them, active vacuum devices are vacuum devices that use microscopic particles. The most common ones are X-ray tubes and neutron tubes, which use electron beams and proton beams to generate X-rays and neutrons respectively, which are used for imaging, material analysis, irradiation and other applications.

[0004] Vacuum high voltage insulation is one of the most critical technologies for high voltage vacuum devices. Unstable operation or even failure of devices is often caused by high voltage breakdown. In high voltage vacuum devices, high voltage breakdown mainly includes vacuum electrode gap breakdown and insulation surface breakdown. Since the threshold of vacuum electrode gap breakdown is much higher than the insulation material surface breakdown, various insulation technologies are focused on surface breakdown, such as using conical insulators to reduce the probability of secondary electron multiplication, using coatings on ceramic surfaces to reduce secondary electron emission coefficients and resistivity, and using metal structures to shield triple points, etc.

[0005] For vacuum electrode gap breakdown, generally, the electrode surface curvature radius is increased to reduce the surface electric field, low initial electron emission metal materials are used, and the surface is polished and cleaned to reduce surface field emission, etc.

[0006] The above methods can solve most of the vacuum electrode gap breakdown problems. However, with the increasing popularity of portable applications, in addition, some special applications such as well logging and prospecting have become more and more urgent for device miniaturization. In well logging and prospecting applications, it is necessary to drop the X-ray tube or neutron tube into the detection pipeline; in the detection of some small-aperture objects, it is also necessary to insert the device deep into it. Due to the small diameter of the pipeline or aperture, the outer diameter of the X-ray tube or neutron tube is greatly limited.

[0007] X-ray tubes or neutron tubes are typical high-voltage vacuum devices that need to work at high voltages of more than 100 kilovolts, especially X-ray tubes that require high voltages of more than 270 kV to achieve good detection results. For high-voltage vacuum devices such as X-ray tubes or neutron tubes for well exploration, which have strict outer diameter constraints, the length of the insulating parts can be greatly extended because there is no constraint in the length direction. Therefore, the risk of surface breakdown can be greatly reduced, giving way to insulation risk.

[0008] However, for safety reasons, the device shell is usually grounded, which results in an extremely high field strength on the surface of the high-voltage electrode in the vacuum, reaching more than 20kV / mm, exceeding the threshold of vacuum gap breakdown. Vacuum breakdown will occur between the high-voltage electrode and the metal shell, and the stable operation of the device cannot be guaranteed. More importantly, the vacuum breakdown threshold is very unstable. During the operation of the device, heat and outgassing cause a decrease in vacuum, particle irradiation and particle impact-induced emission, electrode surface contamination, etc., which can easily cause the actual vacuum breakdown threshold to be far lower than the above-mentioned empirical threshold.

[0009] Therefore, it is difficult to increase the working voltage of small diameter X-ray tubes or neutron tubes used for well logging. It is urgent to develop a small diameter high voltage vacuum device with a high voltage / diameter ratio to meet the needs of well logging and portable applications. Utility Model Content

[0010] In view of the above problems in the prior art, the utility model provides a small-diameter high-voltage vacuum device for vacuum insulation replacement.

[0011] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0012] A small-diameter high-voltage vacuum device with vacuum insulation substitution includes a shell and a high-voltage electrode and a ground electrode arranged in the shell. A special-shaped ceramic tube is arranged between the high-voltage electrode and the grounded shell. The special-shaped ceramic tube includes an insulation substitution area, and the insulation substitution area includes an insulation substitution area ceramic tube. The inner wall of the insulation substitution area ceramic tube is provided with an inner insulation substitution conductive layer, and the outer wall of the insulation substitution area ceramic tube is provided with an outer insulation substitution conductive layer. The outer insulation substitution conductive layer is connected to the shell, and the inner insulation substitution conductive layer is connected to the high-voltage electrode. Through this solution, the high electric field on the vacuum surface of the high-voltage electrode and the field emission and vacuum breakdown caused by it are avoided.

[0013] Furthermore, it also includes a surface insulation area, wherein the surface insulation area includes a surface insulation area ceramic tube, one end of the surface insulation area ceramic tube is connected to the insulation replacement area ceramic tube, and the other end extends axially toward the ground electrode. Through this solution, the surface insulation area ceramic is extended to a low electric field area formed by being surrounded by ground potential structures inside and outside, thereby reducing the electric field on the surface of part of the ceramic and suppressing surface discharge breakdown.

[0014] Furthermore, the outer insulating replacement conductive layer of the insulating replacement area extends to the surface insulating area to the same or close axial position as the target, so as to form an outer surface insulating conductive layer on the outer wall of the ceramic tube in the surface insulating area. Through this scheme, a low electric field area is formed by the outer surface insulating conductive layer and the ground electrode which are also at the ground potential, so as to facilitate the implementation of the ceramic surface insulation function in this area.

[0015] Furthermore, a rounded transition structure is adopted at the transition position between the insulation replacement area and the surface insulation area, and at the connection between the special-shaped ceramic tube, the shell and the high-voltage electrode.

[0016] Furthermore, the creeping insulation region has a surface with a 180-degree normal change on a side close to the ground electrode.

[0017] Furthermore, it also includes a coating, which is used to reduce the secondary electron multiplication coefficient and surface resistivity of the surface of the special-shaped ceramic tube.

[0018] Furthermore, there is a weak electric field area between the insulating replacement area ceramic tube and the shell, and between the insulating replacement area ceramic tube and the high voltage electrode.

[0019] Compared with the prior art, the beneficial effects of the utility model are:

[0020] (1) By transferring the main electric field from the vacuum gap to the ceramic component body, the higher threshold and more stable ceramic body breakdown is used instead of the lower threshold and unstable vacuum gap breakdown, achieving higher insulation performance than the traditional vacuum electrode gap breakdown.

[0021] (2) The position of ceramic surface insulation is moved to the low electric field area to greatly reduce the probability of surface breakdown. And by changing the surface normal by 180 degrees, the electron multiplication path is completely cut off at the ceramic end face, which can better ensure the surface insulation performance compared with traditional high-voltage sockets. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a basic structural diagram of the existing active principle high-voltage vacuum device;

[0023] Figure 2 This is a simulation diagram of the electric field on the electrode surface of an existing high-voltage vacuum device;

[0024] Figure 3 This is a schematic diagram of the structure of a small-diameter high-voltage vacuum device for vacuum insulation replacement of the utility model;

[0025] Figure 4 This is a simulation diagram of the electric field in a small-diameter high-voltage vacuum device of the utility model in which the vacuum insulation is replaced;

[0026] Figure 5It is a schematic diagram of the surface breakdown electron multiplication process of the existing active principle high-voltage vacuum device;

[0027] Figure 6 This is a schematic diagram of the surface breakdown electron multiplication process of a small-diameter high-voltage vacuum device of the utility model for vacuum insulation substitution;

[0028] Figure 7 It is a schematic diagram of the structure of a small-diameter high-voltage vacuum device with a vacuum insulation replacement having an absorption electrode and a shielding body.

[0029] Markings in the figure: 1. Shell; 2. Vacuum zone; 3. Coating; 4. Ceramic; 5. Target; 6. Ground electrode; 7. Primary particles; 8. High-voltage electrode; 9. Secondary particles; 10. Electric field; 11. Surface insulation zone; 11-1. Ceramic tube in the surface insulation zone; 11-2. External surface insulation conductive layer; 12. Insulation substitution zone; 12-1. Ceramic tube in the insulation substitution zone; 12-2. External insulation substitution conductive layer; 12-3. Internal insulation substitution conductive layer; 13. Weak electric field zone; 14. Surface breakdown electron multiplication process of conventional insulator; 15. Surface breakdown electron multiplication process of substitution insulator; 16. Absorption electrode; 17. Shield. DETAILED DESCRIPTION

[0030] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0031] In order to solve the problem that the working voltage of small-diameter high-voltage vacuum devices such as X-ray tubes or neutron tubes is always difficult to increase due to vacuum gap breakdown constraints, the utility model provides a small-diameter high-voltage vacuum device with vacuum insulation replacement.

[0032] The basic structure of existing active principle high-voltage vacuum devices is as follows: Figure 1 As shown, it mainly includes a shell 1, a ceramic 4, a high-voltage electrode 8, and a ground electrode 6. The ceramic 4, the high-voltage electrode 8, and the ground electrode 6 are arranged in the shell 1. The shell 1 is a vacuum-sealed tube shell. The tube is evacuated to form a vacuum zone 2. The surface of the ceramic 4 can be coated with a coating 3. An electric field 10 is formed in the vacuum gap. The primary particles 7 are shot toward the target 5 under the action of the electric field between the high-voltage electrode 8 and the ground electrode 6, and are emitted as secondary particles 9 after being reflected by the target 5. Since the shell is grounded, a very high field strength (such as Figure 2 As shown in Figure 1, when the vacuum gap breakdown threshold is exceeded, vacuum breakdown will occur between the high-voltage electrode and the shell, and the stable operation of the device cannot be guaranteed. In addition, during the operation of the device, heat and gas release cause the vacuum degree to drop, particle irradiation and particle impact-induced emission, electrode surface contamination, etc., which can easily cause the actual vacuum breakdown threshold to be far lower than the above empirical threshold.

[0033] The utility model discloses a small-diameter high-voltage vacuum device with vacuum insulation replacement. Figure 3 As shown, a special-shaped ceramic tube is arranged between the high-voltage electrode 8 and the grounded shell 1. The special-shaped ceramic tube includes an insulating replacement area 12 and may further include a surface insulating area 11.

[0034] The insulating replacement area 12 includes an insulating replacement area ceramic tube 12-1, the inner wall of the insulating replacement area ceramic tube is provided with an inner insulating replacement conductive layer 12-3, and the outer wall is provided with an outer insulating replacement conductive layer 12-2, wherein the outer insulating replacement conductive layer 12-2 is connected to the outer shell 1, and the inner insulating replacement conductive layer 12-3 is connected to the high-voltage electrode 8.

[0035] In the insulating replacement area 12, the ceramic is metallized inside and outside to become a conductive layer, the outer conductive layer is connected to the shell, and the inner conductive layer is connected to the high-voltage electrode. Therefore, the voltage difference (electric field 10) between the high-voltage electrode and the shell is fully loaded in the ceramic (such as Figure 4 As shown). The inside and outside of the ceramic tube, because they are in the same potential boundary, become weak electric field areas 13 or only have very low penetration electric fields. Since the field strength of the ceramic body breakdown is generally greater than 30kV / mm, higher than the vacuum breakdown field strength of 20kV / mm, and is not affected by factors such as changes in the vacuum degree inside the device, particles and particle induction, and pollution, its withstand voltage performance is very stable.

[0036] The surface insulating region 11 includes a surface insulating region ceramic tube 11-1, one end of which is connected to an insulating replacement region ceramic tube 12-1, and the other end of which extends axially toward the ground electrode 6. In this embodiment, the outer insulating replacement conductive layer 12-2 of the insulating replacement region 12 extends toward the surface insulating region 11 to an axial position that is the same as or close to that of the target, thereby forming an outer surface insulating conductive layer 11-2 on the outer wall of the surface insulating region ceramic tube 11-1.

[0037] Most of the surface insulation area 11 is in the area far away from the high-voltage electrode 8. Since both the inner and outer sides are at ground potential, the electric field on the ceramic surface is not high, and it is easy to achieve ceramic surface insulation. According to the principle of surface breakdown, in the process of surface breakdown of insulating components, electron multiplication driven by the electric field is the main factor, and the surface insulation area of ​​the utility model is in a low electric field, so the electron multiplication process is significantly weakened; at the same time, there is a 180-degree surface normal change in the surface insulation area of ​​the ceramic tube, which completely cuts off the electron multiplication path at the end face, so that the secondary electrons are received and absorbed by the ground electrode and the tube shell at ground potential, and it is not easy to continue to creep through the outer surface of the ceramic to the outer shell. Compared with the conical surface design of traditional high-voltage sockets, it can better guarantee the surface insulation performance. The difference between the secondary electron breakdown process of traditional insulators and replacement insulators is as follows Figure 5-6 As shown, Figure 5 The electron multiplication process of the conventional insulator along the surface breakdown is shown in Fig. Figure 6The electron multiplication process of the substitutional insulator along the surface breakdown is shown in FIG15.

[0038] In order to improve the surface insulation capability of the replacement insulator, the coating 3 may be used to reduce the secondary electron multiplication factor and the surface resistivity of the surface.

[0039] In order to reduce the electric field strength in the ceramic body, a rounded corner design is preferably adopted at the transition position between the insulation replacement area and the surface insulation area, and at the connection between the ceramic and the inner and outer metal parts.

[0040] On the basis of the above device structure, an absorption electrode 16 and a shielding body 17 can be further provided to form a Figure 7 The vacuum insulation substitution small diameter high voltage vacuum device shown. Specifically: an absorption electrode 16 extending in the axial direction is arranged inside the shell 1 of the device, one end of the absorption electrode 16 is connected to the shell 1, and is connected to the inner wall of the shell 1 on the same side as the target 5. At the same time, a depression is arranged at the end face of the surface insulation area 11, and the other end of the absorption electrode 16 extends toward the surface insulation area 11 and extends into the depression. The absorption electrode 16 has no connection with the depression. The absorption electrode 16 is mainly used to further reduce the electric field along the surface area and absorb the secondary electrons multiplied along the ceramic surface; the inner insulation substitution conductive layer 12 extends toward the surface insulation area and bends outward to form a hook-shaped shielding body 17, and the shielding body 17 is mainly used to shield the triple point and reduce the secondary electrons initially emitted along the surface area.

[0041] In summary, the utility model proposes a small-diameter high-voltage vacuum device with vacuum insulation replacement, which transfers the main electric field from the vacuum gap to the ceramic component body, eliminating the high electric field established by the external potential boundary in the vacuum. The utility model abandons the conventional method of using vacuum gap to isolate high-voltage electrodes, and uses a ceramic body breakdown with a higher threshold and more stable to replace the vacuum gap breakdown with a lower threshold and unstable; at the same time, the position of the ceramic surface insulation is transferred to the low electric field area for surface breakdown isolation, which greatly reduces the probability of surface breakdown.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A small-diameter high-voltage vacuum device with vacuum insulation displacement, comprising a housing and a high-voltage electrode and a ground electrode arranged in the housing, characterized in that: A special-shaped ceramic tube is arranged between the high-voltage electrode and the grounded outer shell, and the special-shaped ceramic tube includes an insulating replacement area, and the insulating replacement area includes an insulating replacement area ceramic tube. The inner wall of the insulating replacement area ceramic tube is provided with an inner insulating replacement conductive layer, and the outer wall of the insulating replacement area ceramic tube is provided with an outer insulating replacement conductive layer. The outer insulating replacement conductive layer is connected to the outer shell, and the inner insulating replacement conductive layer is connected to the high-voltage electrode.

2. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 1, characterized in that: It also includes a surface insulation area, which includes a surface insulation area ceramic tube. One end of the surface insulation area ceramic tube is connected to the insulation replacement area ceramic tube, and the other end extends axially toward one side of the ground electrode.

3. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 2, characterized in that: The outer insulating replacement conductive layer of the insulating replacement area extends toward the surface insulating area, thereby forming an outer surface insulating conductive layer on the outer wall of the ceramic tube in the surface insulating area.

4. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 2, characterized in that: A rounded transition structure is used at the transition position between the insulation replacement area and the surface insulation area, and at the connection between the special-shaped ceramic tube, the shell and the high-voltage electrode.

5. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 2, characterized in that: The creeping insulation region has a surface with a 180-degree normal change on a side close to the ground electrode.

6. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 2, characterized in that: The invention also comprises a coating, wherein the coating is used for reducing the secondary electron multiplication coefficient and the surface resistivity of the surface of the special-shaped ceramic tube.

7. A small-diameter high-voltage vacuum device with vacuum insulation replacement according to claim 1, characterized in that: There is a weak electric field area between the insulating replacement area ceramic tube and the shell, and between the insulating replacement area ceramic tube and the high-voltage electrode.

Images