Ion source structure with high extraction efficiency and sealed neutron tube structure

Abstract

The application discloses a high-extraction-efficiency ion source structure and sealed neutron tube structure; a TiT thin film target is tightly attached to the inner wall of a closed shell; a target grid is tightly attached to the TiT thin film target, and a negative bias voltage is generated by loading a voltage between the target grid and the closed shell; plasma is generated after a voltage is loaded between a discharge anode and a discharge cathode; the scheme is based on the existing vacuum arc discharge ion source structure and is improved in structure; space is reserved between the discharge cathode and the anode grid for free expansion of the plasma, an open expansion space is provided for the plasma, most of the plasma generated by the discharge can expand into the acceleration zone to obtain energy and bombard the target surface, so that the arc current utilization rate can be increased to about 1%, and the neutron yield can be broken through 1*10 10 n / s.

Description

Technical Field

[0001] This invention relates to the field of neutron tube technology, specifically to an ion source structure with high extraction efficiency and a sealed neutron tube structure. Background Technology

[0002] A neutron tube is a small accelerator neutron source that produces neutrons using deuterium-deuterium or deuterium-tritium nuclear reactions. It is a sealed vacuum electro-optical device, mainly consisting of an ion source, a beam acceleration and transmission structure, a target, and a sealed casing. The neutron tube ion source generates deuterium ions through glow discharge or arc discharge, which are then accelerated under a high-voltage electric field to bombard a deuterium or tritium target, producing neutrons. Neutron tubes offer advantages such as small size, safety and controllability, and portability, and are widely used in fields such as oil well logging, elemental analysis, and explosives detection.

[0003] Typical neutron tube ion sources use Penning discharge mode, with an ionization efficiency of less than 1%, and an effective single-atom deuterium ion ratio of less than 10%. The deuterium ion beam current is weak, and the neutron yield is generally only 10. 8 n / s. Later, some neutron tubes used vacuum arc discharge or RF discharge as the ion source, which increased the density and proportion of single-atom deuterium ions, resulting in a high-current deuterium ion beam and increasing the neutron yield to 10. 9 To facilitate beam extraction and transmission, the extraction aperture size of ion sources is typically tens of millimeters. Most of the plasma is lost due to collisions with the walls within the expansion cup, resulting in very low utilization efficiency. For example, the ion current in plasma generated by vacuum arc discharge accounts for about 10% of the discharge current intensity, but the actual utilization rate is far less than 1%. The most typical example is the ING series neutron tubes developed by the All-Russian Scientific Research Institute of Automation in Russia. The vacuum arc discharge current is close to 1000A, but the extracted deuterium ion current is only about 100mA, with an efficiency of only 0.01%. Furthermore, RF ion sources need to operate under a pressurized atmosphere. To load a high voltage of around 100kV, the pressure cannot be too high, which also limits the magnitude of the deuterium ion current. Most seriously, the beam spot size on the target surface of conventional neutron tubes is typically tens of millimeters, resulting in a very high deposition power density. Simply increasing the discharge current intensity or acceleration energy to increase the neutron yield will cause target damage. Therefore, a neutron yield of 10... 9 n / s is roughly the limit for neutron tubes.

[0004] Because neutrons are uncharged, they rarely react with elements, resulting in weak gamma signals and low signal-to-noise ratios in elemental analysis. Accurate analytical results require long periods of cumulative interaction. Increasing the neutron yield in neutron tubes would significantly shorten analysis time and is crucial for improving neutron utilization efficiency. Summary of the Invention

[0005] The technical problem this invention aims to solve is that the production volume of sealed neutron tubes is difficult to exceed 1×10⁻⁶. 10The present invention aims to provide a high extraction efficiency ion source structure and neutron tube. Based on the isotropic uniform expansion law of vacuum arc discharge plasma, the existing vacuum arc discharge ion source structure is improved by setting the ion source expansion cup to a hemispherical or cylindrical shape, providing a sufficiently open expansion space for the plasma, so that the plasma generated by the discharge can expand into the acceleration region to obtain energy and bombard the target surface, thereby increasing the arc current utilization rate to about 1%. This solution improves the plasma utilization efficiency and reduces the target surface deposition power density by improving the neutron tube ion source expansion cup and extraction structure, thus breaking through the limit of the highest neutron yield of the neutron tube.

[0006] This invention is achieved through the following technical solution:

[0007] This scheme provides a high extraction efficiency ion source structure, including: a discharge cathode, a discharge anode, and an anode grid; the discharge anode and discharge cathode are used to generate plasma, and a space is reserved between the discharge anode and the anode grid for the free expansion of the plasma. In this scheme, the space formed by the discharge cathode and the anode grid has the same distribution pattern as the free expansion space of the plasma, which improves the plasma utilization efficiency.

[0008] This solution also provides a high extraction efficiency sealed neutron tube structure, including: a discharge anode, a discharge cathode, an anode grid, a target grid, a TiT thin film target, and a sealed shell;

[0009] The discharge anode, discharge cathode target grid, and TiT thin film target are all disposed inside a closed housing, with the TiT thin film target closely attached to the inner wall of the closed housing;

[0010] The target grid is close to the TiT thin film target, and a negative bias voltage is generated by applying a voltage between the target grid and the enclosed shell.

[0011] The discharge anode is close to the discharge cathode, and plasma is generated after a voltage is applied between the discharge anode and the discharge cathode;

[0012] A space is reserved between the discharge anode and the anode grid to allow the plasma to expand freely.

[0013] The working principle of this invention is as follows: This invention aims to provide an ion source structure and neutron tube structure for vacuum arc discharge. Based on the isotropic uniform expansion law of vacuum arc discharge plasma, it improves the existing vacuum arc ion source structure by setting the ion source expansion cup to a hemispherical or cylindrical shape, and reserving space between the discharge anode and the anode grid for free plasma expansion. This allows the plasma generated by the discharge to expand into the acceleration zone, gain energy, and bombard the target surface, thereby increasing the arc current utilization rate to approximately 1% and achieving a neutron yield exceeding 1×10⁻⁶. 10 n / s.

[0014] Under the extremely high pressure inside the cathode spot, the plasma generated by the vacuum arc discharge ion source expands almost uniformly outwards. Conventional ion source structures utilize only a small portion of the plasma along its axis, with the remainder collapsing against the expansion cup walls and becoming neutral particles, resulting in the loss of deuterium ions and beam current. This proposed vacuum arc discharge ion source, based on an open expansion space, allows the plasma to expand freely in the open space between the cathode and anode grids, avoiding the problems of high deuterium ion loss due to wall collisions and low utilization rates found in conventional vacuum arc ion sources. This achieves a neutron yield exceeding 1×10⁻⁶. 10 n / s.

[0015] In this scheme, the target grid is close to the TiT thin film target. The target surface of the target grid is a large-area curved target, which can effectively reduce the power density of the ion beam deposited on the target surface without causing target damage, so that the ion source structure can work for a long time. The TiT thin film target is a thin film deposited on the tube wall, which can form various irregular structures. The TiT thin film target substrate is a metal material with high thermal conductivity such as Cu and Al alloy. If necessary, cooling water can be passed through the outside of the metal substrate to further reduce the target surface temperature.

[0016] When high-energy ions bombard the target surface, a large number of secondary electrons are generated simultaneously. These secondary electrons are then drawn back by the high-voltage electric field to bombard the ion source, causing damage to ion source components, extremely high beam load, and even high-voltage breakdown. To solve this problem, a target grid is placed in front of the target, serving as both an extraction electrode and forming a negative voltage with the target to prevent the secondary electron beam from back-bombarding the ion source structure. To extend the surface distance between the anode and cathode of the ion source structure and the target, the target is placed in the middle of the neutron tube, allowing the neutron tube to operate normally even under very high voltages.

[0017] A further optimized solution is that the enclosed shell includes a metal part and an insulating ceramic part; the plasma accelerates freely in the direction of the metal part;

[0018] The TiT thin film target is attached tightly to the inner wall of the metal part.

[0019] A further optimized scheme involves using an anode grid as the discharge anode, which is then wrapped around the discharge cathode. This scheme directly uses the grid as the anode, allowing the plasma more space to expand freely within the same volume of enclosed casing, avoiding losses due to collisions with walls and improving plasma utilization.

[0020] A further optimized scheme is that the discharge cathode includes: a TiD cathode, a trigger ceramic, and a cathode feed electrode. The TiD cathode is close to the discharge anode, and the applied voltage is applied to the TiD cathode through the cathode feed electrode and the trigger ceramic.

[0021] A further optimized solution is that the enclosed shell is a hollow cylinder, and the height of the hollow cylinder is greater than the diameter of the bottom circle;

[0022] The discharge cathode is located at the center of the hollow cylinder. The anode grid is a hollow circular tube surrounding the discharge cathode. The height of the hollow circular tube is greater than the diameter of the bottom circle. The center of the hollow cylinder coincides with the center of the hollow circular tube. The metal part of the enclosed shell is a first hollow circular tube, which is wrapped around the outer edge of the hollow circular tube.

[0023] A further optimized solution is that the metal part of the enclosed shell is a hollow hemisphere, and the insulating ceramic part is a cylindrical groove, with the hollow hemisphere matching and covering the insulating ceramic part; the anode grid is a hollow hemisphere that coincides with the center of the metal part.

[0024] The discharge cathode is located at the center of the hollow hemisphere.

[0025] A further optimized scheme is that the discharge anode includes a positive electrode and an anode feed electrode, the positive electrode is close to the discharge cathode, and the applied voltage is applied to the positive electrode through the anode feed electrode.

[0026] A further optimized solution includes a first anode grid and a thin-film resistor;

[0027] The anode is a ring-shaped electrode with a thickness of m, and the TiD cathode is a cylinder. The TiD cathode is disposed inside the ring of the anode, and the centerline of the TiD cathode coincides with that of the anode. An insulating ring is filled between the TiD cathode and the anode.

[0028] The first anode grid, target grid, TiT thin film target, thin film resistor, and metal part are hemispheres with successively increasing sphere radii. The TiT thin film target and the thin film resistor are in close contact, and the thin film resistor and the metal part are in close contact. The sphere radius of the first anode grid is equal to the outer ring radius of the anode, and the first anode grid covers the anode.

[0029] The insulating ceramic portion is a cylindrical groove, and the metal portion covers the insulating ceramic portion.

[0030] A further optimization scheme involves setting a bias power supply, a self-biasing resistor, or a thin-film resistor between the target grid and the TiT thin-film target to generate a negative bias voltage, wherein the TiT thin-film target is applied with a positive electrode and the target grid is applied with a negative electrode.

[0031] Both the insulating ceramic portion and the trigger ceramic are semiconductor-doped ceramics or surface-coated ceramics. Semiconductor-modified materials can reduce the surface resistivity of the ceramic, thereby increasing its surface withstand voltage and operating voltage.

[0032] The neutron tube operation of this invention is as follows: First, a voltage is applied between the discharge anode and the discharge cathode, causing vacuum breakdown discharge and generating seed electrons; then, under the action of the electric field between the discharge electrodes, the discharge anode and the discharge cathode transform into a vacuum arc with an arc current of approximately 10A to 1kA, generating a density of 10A near the cathode spot. 16 ~10 20 cm -3 The deuterium ions expand freely in all directions, pass through the anode grid, are accelerated by an 80–200 kV high voltage, and then bombard the TiT thin film target on the metal part of the tube wall, producing high-yield neutrons. A negative voltage of 2–10 kV is applied between the target grid and the TiT thin film target to suppress secondary electrons generated by the ion beam bombardment of the target, reduce the load on the high-voltage power supply, and reduce the risk of high-voltage breakdown. The neutron tube in this scheme operates in pulsed mode, with a single discharge arc current of 10 A–1 kA, a duration of 0.5 μs to 10 ms, an operating frequency of 1 Hz–50 Hz, a target diameter of 150–300 mm, and a maximum yield of 10 11 n / s pulsed neutrons.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] This invention provides a high extraction efficiency ion source structure and a sealed neutron tube structure. Based on existing vacuum arc discharge ion source structures, structural improvements are made. The discharge cathode and anode grid form an open space for free plasma expansion, allowing most of the plasma generated by the discharge to expand into the acceleration region, gain energy, and bombard the target surface. This increases the arc current utilization rate to approximately 1%, achieving a neutron yield exceeding 1×10⁻⁶. 10 n / s.

[0035] This invention provides a high extraction efficiency ion source structure and a sealed neutron tube structure. Through designs such as vacuum arc discharge, open space expansion structure, vacuum working environment, large target surface, and semiconductor-modified ceramics, it can significantly improve the target deuterium ion current intensity and operating voltage, thereby achieving 10 11 Neutron yield with an intensity of n / s. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0037] Figure 1 This is a schematic diagram of the high extraction efficiency sealed neutron tube structure of Example 2;

[0038] Figure 2 This is a schematic diagram of the high extraction efficiency sealed neutron tube structure in Example 3;

[0039] Figure 3 A schematic diagram showing the setting of a bias power supply between the target grid and the enclosed housing;

[0040] Figure 4 A schematic diagram showing the placement of a self-biasing resistor between the target grid and the enclosed housing;

[0041] Figure 5 A schematic diagram showing the placement of a thin-film resistor between the target grid and the enclosed housing;

[0042] Figure 6 Schematic diagram A of the high extraction efficiency ion source structure in Example 4;

[0043] Figure 7 Schematic diagram B of the high extraction efficiency ion source structure in Example 4;

[0044] Figure 8 A schematic diagram of the principle of an ion source for vacuum arc discharge;

[0045] Figure 9 This is a schematic diagram of the plasma spatial distribution characteristics in Example 4.

[0046] The attached diagram shows the markings and corresponding component names:

[0047] 1-Discharge anode, 11-Anode, 12-Discharge cathode, 22-Discharge cathode, 21-TiD cathode, 22-Trigger ceramic, 23-Cathode feed electrode, 3-Target grid, 4-TiT thin film target, 5-Enclosed shell, 51-Metal part, 52-Insulating ceramic part, 6-First anode grid, 7-Thin film resistor, 8-Cathode feed rod, 9-Insulating ring. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0049] In existing neutron tube ion sources, the discharge cavity is mostly bordered by metal, and plasma can only form a beam through the extraction aperture. Most of the plasma is lost due to wall collisions, resulting in very low utilization efficiency. For example, the ion current in the plasma generated by vacuum arc discharge accounts for about 10% of the discharge current intensity, but the actual utilization rate is far less than 1%. The size of the ion source extraction aperture is typically tens of millimeters, and the beam spot size for target application is also on the order of tens of millimeters. The power density deposited on the target surface is very high. Simply increasing the discharge current intensity or acceleration energy to increase the neutron yield will cause target damage. Therefore, a neutron yield of 10... 9 n / s is roughly the limit for neutron tubes. Further increasing neutron yield requires the use of large-scale equipment such as voltage doublers, which restricts the application of neutrons. To improve the ion source expansion and extraction structure of neutron tubes, increase plasma utilization efficiency, reduce target deposition power density, and overcome the maximum neutron yield limit of neutron tubes, this invention provides the following embodiments to solve the above-mentioned technical problems:

[0050] Example 1

[0051] High-density vacuum arc ion sources provide deuterium ions. A vacuum arc is a discharge phenomenon occurring in a vacuum environment. Its typical characteristic is that the plasma properties are primarily generated by the cathode spot on the cathode surface and the surrounding collisional relaxation region. Outside this region, the plasma no longer collides with each other, forming a free expansion region. The cathode spot diameter is approximately 1 μm, and the relaxation region size is less than 100 μm. Both of these dimensions are extremely small, while the plasma density is as high as 10⁻⁶. 16 ~10 20 cm -3 Therefore, collisions between particles are very frequent, the plasma is in thermal equilibrium, and its expansion velocity is isotropic, meaning it moves uniformly in all directions, such as... Figure 8 As shown.

[0052] This embodiment describes the plasma expansion pattern formed by vacuum arc discharge and designs a novel expansion and extraction structure, providing a high extraction efficiency ion source structure, including: a discharge cathode, a discharge anode, and an anode grid; the discharge anode and discharge cathode are used to generate plasma, and a space is reserved between the discharge anode and the anode grid for the free expansion of the plasma. The spatial distribution of the discharge cathode and anode grid is consistent with the free expansion space of the plasma, improving plasma utilization.

[0053] Example 2

[0054] This embodiment provides a high extraction efficiency sealed neutron tube structure, including: a discharge anode 1, a discharge cathode 2, a target grid 3, an anode grid, a TiT thin film target 4, and a sealed shell 5; the discharge cathode 2 is surrounded by trigger ceramics and trigger electrodes to generate seed electrons.

[0055] The discharge anode 1, discharge cathode 2, target grid 3, and TiT thin film target 4 are all disposed inside the enclosed housing 5, and the TiT thin film target 4 is in close contact with the inner wall of the enclosed housing 5.

[0056] The target grid 3 is close to the TiT thin film target 4, and a negative bias voltage is generated by applying a voltage between the target grid 3 and the enclosed shell 5.

[0057] The discharge anode 1 is close to the discharge cathode 2, and plasma is generated after a voltage is applied between the discharge anode 1 and the discharge cathode 2.

[0058] A space is reserved between the discharge anode 1 and the anode grid to allow the plasma to expand freely.

[0059] The enclosed shell 5 includes a metal part 51 and an insulating ceramic part 52; the plasma accelerates freely toward the anode grid;

[0060] The TiT thin film target 4 is attached tightly to the inner wall of the metal part 51.

[0061] The discharge anode 1 is an anode grid; the anode grid will wrap around the discharge cathode 2.

[0062] The discharge cathode 2 includes a TiD cathode 21, a trigger ceramic 22, and a cathode feed electrode 23. The TiD cathode 21 is close to the discharge anode 1, and the applied voltage is applied to the TiD cathode 21 through the cathode feed electrode 23 and the trigger ceramic 22.

[0063] Example 3

[0064] like Figure 1 As shown, based on Embodiment 1, the closed outer shell 5 of this embodiment is a hollow cylinder, and the height of the hollow cylinder is greater than the diameter of the bottom circle;

[0065] The discharge cathode 2 is located at the center of the hollow cylinder. The anode grid is a hollow tube wrapped around the discharge cathode 2. The height of the hollow tube is greater than the diameter of the bottom circle. The center of the hollow cylinder coincides with the center of the hollow tube. The metal part 51 of the enclosed shell 5 is a first hollow tube, which is wrapped around the outer shell of the hollow cylinder. The anode feed electrode is connected to the discharge anode 1, and the cathode feed electrode is connected to the discharge cathode 2.

[0066] Example 4

[0067] like Figure 2 As shown, based on Embodiment 1, the metal part 51 of the closed shell 5 in this embodiment is a hollow hemisphere, and the insulating ceramic part 52 is a cylindrical groove. The hollow hemisphere matches and covers the insulating ceramic part 52. In this embodiment, the discharge anode 1 is also an anode grid, and the anode grid is a hollow hemisphere that coincides with the center of the metal part 51.

[0068] The discharge cathode 2 is located at the center of the hollow hemisphere.

[0069] Example 5

[0070] like Figure 6 and Figure 7 As shown, based on Example 1, the discharge anode 1 of this embodiment includes a positive electrode 11 and an anode feed electrode 12. The positive electrode 11 is close to the discharge cathode 2, and the applied voltage is applied to the positive electrode 11 through the anode feed electrode 12.

[0071] This embodiment also includes a thin-film resistor 7, wherein the anode grid is a first anode grid 6;

[0072] The anode 11 is a ring-shaped electrode with a thickness of m. The TiD cathode 21 is a cylinder. The TiD cathode 21 is disposed inside the ring of the anode 11. The centerline of the TiD cathode 21 coincides with that of the anode 11. An insulating ring 9 is filled between the TiD cathode 21 and the anode 11. The TiD cathode 21 is loaded with voltage through the cathode feed rod 8.

[0073] The first anode grid 6, target grid 3, TiT thin film target 4, thin film resistor 7 and metal part 51 are hemispheres with successively increasing sphere radii. The TiT thin film target 4 and the thin film resistor 7 are in close contact, and the thin film resistor 7 and the metal part 51 are in close contact. The sphere radius of the first anode grid 6 is equal to the outer ring radius of the anode 11, and the first anode grid 6 covers the anode 11.

[0074] The insulating ceramic portion 52 is a cylindrical groove, and the metal portion 51 is matched and covered on the insulating ceramic portion 52.

[0075] A high voltage of 2–10 kV is applied to discharge anode 1 and discharge cathode 2. A surface flashover discharge occurs in the insulating ceramic between them, providing seed electrons, which in turn induces a vacuum arc discharge between the cathode and anode, generating high-density plasma. The cathode material is a deuterium-containing metal, such as TiD or ZrD. The insulating ring can be made of mica, alumina ceramic, quartz glass, or other materials. This ion source is triggered by the insulating ceramic between the cathode and anode, requiring no additional trigger electrode, resulting in a simple structure. A hemispherical anode grid serves as an expansion and extraction structure outside the cathode and anode, and it is at the same potential as the anode. After the plasma is generated on the cathode surface, it expands isotropically towards the anode grid, and after being accelerated by the electric field through the anode grid, it strikes the target.

[0076] Figure 9The figure shows the experimentally measured spatial distribution characteristics of the plasma, with the values ​​representing relative values ​​of the density logarithmic function. As can be seen, the plasma expands outward in a hemispherical shape, corresponding precisely to the hemispherical anode grid. In the newly designed ion source, the plasma is absorbed only by the grid lines in the expansion region, resulting in very high extraction efficiency. A high-current deuterium ion beam can be obtained without increasing the discharge current.

[0077] A large-diameter spherical TiT thin film target can effectively reduce the ion beam power density deposited on the target surface without causing target damage, thus allowing the neutron tube to operate for extended periods. To extend the surface distance between the ion source anode and cathode and the target, the ion source is placed in the middle of the neutron tube. Through these structural designs, the operating voltage of the neutron tube can be increased to 200 kV.

[0078] In this embodiment, a hemispherical anode grid serves as an expansion and extraction structure outside the cathode and anode, and it is at the same potential as the anode. After the plasma is generated on the cathode surface, it expands isotropically towards the anode grid, and after being accelerated by the electric field through the anode grid, it strikes the target. This ion source can effectively extract almost all of the generated plasma. Considering ineffective metal ions, the utilization efficiency is about 1%, and a high-current deuterium ion beam in the ampere range can be obtained under a 100-ampere arc current, which is two orders of magnitude more efficient than the vacuum arc ion source developed in Russia.

[0079] Example 6

[0080] Based on the above embodiments, this embodiment sets a bias power supply, a self-biasing resistor or a thin film resistor between the target grid 3 and the TiT thin film target to generate a negative bias voltage, wherein the TiT thin film target is applied with a positive electrode and the target grid 3 is applied with a negative electrode.

[0081] The structure of setting a bias power supply between the target grid 3 and the TiT thin film target is as follows: Figure 3 As shown, a negative bias voltage is generated between the target grid and the TiT thin film, allowing secondary electrons generated by ion bombardment of the target to be absorbed by the target. The structure with a self-biased resistor between the target grid 3 and the TiT thin film target is shown below. Figure 4 As shown, an external resistor of 1–10 kΩ is connected. When the ion flow passes through the self-biased resistor, a negative bias voltage is generated between the target grid and the TiT thin film, which also allows the secondary electrons generated by ion bombardment of the target to be absorbed by the target. The structure of setting a thin film resistor between the target grid 3 and the TiT thin film target is as follows. Figure 5 As shown, the self-biased resistor is designed as a thin film and embedded between the TiT thin film and the metal shell to form an integrated structure, which can also generate a negative bias voltage between the target grid and the TiT thin film.

[0082] Both the insulating ceramic portion 52 and the triggering ceramic portion 22 are semiconductor-doped ceramics or surface-coated ceramics.

[0083] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sealed neutron tube structure with high extraction efficiency, characterized in that, include: Discharge anode (1), discharge cathode (2), target grid (3), anode grid, TiT thin film target (4) and enclosed shell (5); The discharge anode (1), discharge cathode (2), target grid (3) and TiT thin film target (4) are all disposed inside the closed shell (5), and the TiT thin film target (4) is in close contact with the inner wall of the closed shell (5); The target grid (3) is close to the TiT thin film target (4), and a negative bias voltage is generated by applying a voltage between the target grid (3) and the closed shell (5); The discharge anode (1) is close to the discharge cathode (2), and plasma is generated after a voltage is applied between the discharge anode (1) and the discharge cathode (2); A space is reserved between the discharge anode (1) and the anode grid to allow for the free expansion of the plasma; The enclosed shell (5) includes a metal part (51) and an insulating ceramic part (52); the plasma accelerates freely toward the metal part (51); The TiT thin film target (4) is attached to the inner wall of the metal part (51); The discharge cathode (2) includes: a TiD cathode (21), a trigger ceramic (22) and a cathode feed electrode (23). The TiD cathode (21) is close to the discharge anode (1), and the applied voltage is applied to the TiD cathode (21) through the cathode feed electrode (23) and the trigger ceramic (22). The metal part (51) of the closed shell (5) is a hollow hemisphere, and the insulating ceramic part (52) is a cylindrical groove. The hollow hemisphere is matched and covered on the insulating ceramic part (52). The anode grid is a hollow hemisphere that coincides with the center of the metal part (51). The discharge cathode (2) is located at the center of the hollow hemisphere; The discharge anode (1) includes a positive electrode (11) and an anode feed electrode (12). The positive electrode (11) is close to the discharge cathode (2), and the applied voltage is applied to the positive electrode (11) through the anode feed electrode (12). It also includes thin-film resistors (7); The anode grid is a first anode grid (6), the anode (11) is a ring-shaped electrode with a thickness of m, the TiD cathode (21) is a cylinder, the TiD cathode (21) is disposed inside the ring of the anode (11), the center line of the TiD cathode (21) coincides with that of the anode (11), and an insulating ring (9) is filled between the TiD cathode (21) and the anode (11). The first anode grid (6), target grid (3), TiT thin film target (4), thin film resistor (7) and metal part (51) are hemispheres with successively increasing sphere radii. The TiT thin film target (4) and thin film resistor (7) are in close contact, and the thin film resistor (7) and metal part (51) are in close contact. The sphere radius of the first anode grid (6) is equal to the outer ring radius of the anode (11), and the first anode grid (6) covers the anode (11). The insulating ceramic portion (52) is a cylindrical groove, and the metal portion (51) is matched and covered on the insulating ceramic portion (52).

2. The high extraction efficiency sealed neutron tube structure according to claim 1, characterized in that, The discharge anode (1) serves as an anode grid; the anode grid will be wrapped around the discharge cathode (2).

3. The high extraction efficiency sealed neutron tube structure according to claim 2, characterized in that, The enclosed shell (5) is a hollow cylinder, and the height of the hollow cylinder is greater than the diameter of the bottom circle; The discharge cathode (2) is located at the center of the hollow cylinder. The anode grid is a hollow tube wrapped around the discharge cathode (2). The height of the hollow tube is greater than the diameter of the bottom circle. The center of the hollow cylinder coincides with the center of the hollow tube.

4. The high extraction efficiency sealed neutron tube structure according to claim 1, characterized in that, A bias power supply, a self-biasing resistor, or a thin film resistor is provided between the target grid (3) and the TiT thin film target (4) to generate a negative bias voltage, wherein the TiT thin film target (4) is applied with a positive electrode and the target grid (3) is applied with a negative electrode.

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