Open tube type miniature X-ray tube with adjustable anode and experiment evaluation platform of open tube type miniature X-ray tube

Abstract

The invention discloses an open tube type miniature X-ray tube with an adjustable anode and an experiment evaluation platform of the open tube type miniature X-ray tube, and belongs to the technical field of miniature micro-focal spot X-ray tubes. An X-ray tube emission and experiment platform of the system is formed by assembling an open tube type miniature X-ray tube system and an experiment platform. The open tube type miniature X-ray tube system comprises a hot cathode filament, an electrostatic lens focusing system and an anode target material; the experiment evaluation system comprises a vacuum cavity, and an electric input interface, a vacuum input interface and the like which are matched with the vacuum cavity. And the distance between the cathode and the anode can be adjusted by using a positioning hole in the electronic optical system. The experiment evaluation system fixes the electron optical system, and provides experiment conditions such as a high vacuum environment, acceleration voltage and heating current required by an experiment at the same time. According to the invention, the anode-adjustable open tube experiment of the miniature X-ray tube is realized, and compared with a closed tube experiment, the open tube is convenient for adjusting the design of the miniature X-ray tube, and the experiment cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of micro X-ray tube cathode optical structures, and in particular relates to an experimental method for optimizing the micro X-ray tube cathode structure. Background Art

[0002] Ordinary micro X-ray tubes are limited by volume and often use a closed tube structure that does not require an additional vacuum system. The closed tube structure requires the X-ray tube to be sealed in advance, and the sealing process is complicated, which burdens the experimental time. At the same time, the X-ray tube with a closed tube structure cannot be repaired once it is damaged, which cannot meet the needs of experimental convenience.

[0003] Electron optical design is often simulated with the help of electron optical software, but simulation often requires some approximations to facilitate calculation, which often results in errors between the simulation results and the actual situation, and simulation often cannot determine the optimal electron optical structure.

[0004] In order to determine a better micro X-ray tube structure through experiments, an experimental method suitable for micro X-ray tubes is needed which can save both experimental time and cost. Summary of the invention

[0005] The technical problem solved by the present invention is to propose an open-tube micro X-ray tube with adjustable anode and an experimental platform structure thereof, which is more conducive to experimental evaluation of the performance of micro X-ray tubes with different electronic optical structures, saving experimental time and experimental costs.

[0006] The purpose of the present invention can be achieved through the following technical solutions: an open-tube micro X-ray tube with adjustable anode: the end of the open-tube micro X-ray tube is a grid fixing ring, the grid fixing ring is fixed to the grid by threads, the filament is fixed to the grid by a top screw, the rear end of the grid fixing ring is a metal flange, which can be connected to an aviation plug to achieve vacuum sealing and provide actual voltage and filament heating current at the same time; an insulator is compactly placed at the front end of the grid fixing ring, and a positioning hole is provided at the front end of the insulator for fixing the anode position; an electron beam channel is provided at the center of the anode, and the X-ray anode target is fixed at the anode exit position by welding, and several insulating gaskets can be added between the grid fixing ring and the insulator for adjusting the distance between the anode and the cathode; the relative positions of the grid and the anode are fixed by the positioning holes on the outer positioning ceramic body and the positioning insulating column. The experimental platform for realizing the open-tube micro X-ray tube is a metal cavity with flanges on all six sides, the open-tube micro X-ray tube is fixedly connected by the rear flange, and the front flange is fixed with a high X-ray transmittance sealing window, and the X-ray passes through the sealing window and is received by the detector. The left and right flanges are used to connect the vacuum system and the vacuum measurement system. The upper flange is connected to the vacuum high-voltage insulated electrode to provide the anode voltage, and the lower flange can be used in conjunction with the X-ray evaluation method and equipped with an evaluation device.

[0007] The present invention has the following beneficial effects:

[0008] 1. The present invention replaces the closed-tube structure with an open-tube micro X-ray tube structure, thereby avoiding the sealing process required for the closed-tube structure. At the same time, the entire system except the anode target is mechanically connected, avoiding the welding process, thereby saving experimental time and cost.

[0009] 2. The present invention adopts an adjustable anode mechanical connection, and the anode position can be adjusted by adding or reducing the number of insulating gaskets, without the need to reprocess parts, saving time and cost, and facilitating experimental evaluation of different structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A cross-sectional view of an open-tube micro X-ray tube with adjustable anode and an experimental platform thereof proposed by the present invention;

[0011] Figure 2 A cross-sectional view of an open-tube micro X-ray tube with adjustable anode proposed by the present invention;

[0012] In the figure, 1, hot cathode filament; 101, pure metal hot cathode; 102, filament terminal; 103, ceramic body; 2, grid; 3, electron beam; 4, anode; 5, anode target; 501, heavy metal target material coating; 502, anode substrate; 6, insulator; 7, positioning insulator; 8, grid fixing ring; 9, insulating gasket; 10, insulating positioning column; 11, vacuum chamber; 12, vacuum high-voltage insulating electrode; 13, high X-ray transmittance sealing window; 14, high vacuum flange; 15, X-ray. DETAILED DESCRIPTION

[0013] The present invention will be explained below in conjunction with the drawings in the embodiments of the present invention. The description in this part is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0014] Please refer to Figure 1-Figure 2 In the present invention, an open-tube micro X-ray tube with adjustable anode and an experimental platform thereof include: a hot cathode filament 1, a pure metal hot cathode 101, a filament terminal 102, a ceramic body 103, a grid 2, an anode 4, an anode target 5, a heavy metal target material coating 501, an anode substrate 502, an insulator 6, a positioning insulator 7, a grid fixing ring 8, an insulating gasket 9, an insulating positioning column 10, a vacuum cavity 11, a vacuum high-voltage insulating electrode 12, a high X-ray transmittance sealing window 13, and a high vacuum flange 14; the grid fixing ring 8, the anode 4, and the insulator 6 are all fixed on the positioning insulator 7, the hot cathode filament 1 is fixed on the grid 2, and is fixed with the grid 2 and the grid fixing ring 8, and the grid fixing ring 8, the vacuum high-voltage insulating electrode 12, the high X-ray transmittance sealing window 13, and the high vacuum flange 14 are all fixed on the vacuum cavity 11;

[0015] The pure metal hot cathode 101 is used to emit electrons. A commercially mature hot cathode such as a tungsten filament or lanthanum hexaboride can be selected. The hot cathode can be fixed to the filament terminal 102 by pressure welding. A heating current is provided through the filament terminal to make the hot cathode reach the working temperature to achieve electron emission. The advantages of tungsten filament and lanthanum hexaboride cathode are that the electron beam spot is small and the implementation is simple. The filament terminal 102 is fixed to the ceramic body 103 by brazing. A positioning groove is opened on the ceramic body 103, and it is fixed and assembled with the grid 2 by a top screw.

[0016] The grid 2 is in the shape of a pencil formed by a combination of a hollow cylinder and a hollow truncated cone, with a limiting hole in the center for controlling the size of the beam spot of the emitted electron beam 3, and a number of circular holes with slightly larger apertures are opened around the limiting hole for adjusting the electric field distribution on the cathode surface; the grid 2 is preferably made of high temperature resistant and electron beam bombardment resistant materials such as molybdenum, rhenium, and tungsten; the grid 2 is provided with a thread on the outside, and is fixed to the grid fixing ring 8 through the thread;

[0017] The insulator 6 is a hollow cylindrical structure, used for electrical insulation between the grid and the anode. A positioning hole is opened at the front end of the insulator 6, which cooperates with the positioning hole on the anode 5 to achieve fixation between the two. The insulator 6 is preferably made of a material such as polytetrafluoroethylene with good insulation and easy processing;

[0018] The anode 5 is an axisymmetric cylindrical structure with a limiting hole, loaded with a positive high voltage of 10-50kV. The anode substrate 502 is connected to the anode 5 by welding, and at the same time, a heavy metal target coating 501 is plated on the anode substrate 502 by a metal coating process. The electron beam 3 is accelerated by the anode 5 and bombards the heavy metal target coating 501 to generate X-rays. The anode 5 is preferably made of high temperature resistant and electron beam bombardment resistant materials such as molybdenum, rhenium, and tungsten, and the heavy metal target coating 501 is preferably made of high atomic number metals such as tungsten; the anode substrate 502 needs to be made of a material with a low atomic number, good electrical conductivity, and good thermal conductivity, such as diamond; the front and rear ends of the anode 5 are all surrounded by positioning holes, the front end positioning hole cooperates with the insulator 6, and the rear end positioning hole is fixedly matched with the positioning insulator 7;

[0019] Positioning holes are opened around the front and rear parts of the positioning insulator 7 to achieve relative fixation of the micro X-ray tube as a whole. The front positioning holes are evenly distributed to achieve fixed connection with the grid fixing ring 8. The rear end is provided with spiral rising positioning holes. After adding different numbers of insulating gaskets 9, the positioning holes on the anode 5 need to be matched with the positioning holes in different directions on the positioning insulator 7 to achieve fixation; the positioning insulator 7 and the insulating gasket 9 are preferably made of polytetrafluoroethylene;

[0020] The micro X-ray tube as a whole is fixedly connected to the vacuum chamber 11 through the metal flange on the grid fixing ring 8, and the aviation plug can be connected through the metal flange to achieve the sealing of the micro X-ray tube and provide heating current for the hot cathode;

[0021] The vacuum chamber 11 has flange interfaces on six sides, which are respectively connected to the micro X-ray tube, the vacuum system, the vacuum high-voltage ceramic electrode 12, and the high X-ray transmittance sealing window 14;

[0022] The high-voltage vacuum insulated electrode 12 is connected to the vacuum chamber 11 through a flange to provide an accelerating voltage of 0-50 kV for the anode;

[0023] The high X-ray transmittance sealing window 13 is fixedly connected to the vacuum chamber 11 through the high vacuum flange 14; the high X-ray transmittance sealing window 13 is preferably made of a material with high X-ray transmittance and good sealing performance, such as polypropylene;

[0024] The specific embodiments described in the present invention are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

Claims

1. An open-tube micro X-ray tube with adjustable anode, characterized in that: The end of the open-tube micro X-ray tube is a grid fixing ring. The grid fixing ring (8) is fixed to the grid (2) by means of threads. The hot cathode filament (1) is fixed to the grid (2) by means of a top screw. The rear end of the grid fixing ring (8) is a metal flange that can be connected to an aviation plug to achieve vacuum sealing and provide actual voltage and filament heating current. An insulator (6) is compactly placed at the front end of the grid fixing ring (8). A positioning hole is provided at the front end of the insulator (6) for fixing the position of the anode (4). An electron beam channel is provided at the center of the anode (4). An X-ray anode target (5) is fixed at the exit position of the anode (4) by welding. A plurality of insulating gaskets (9) can be added between the grid fixing ring (8) and the insulator (6) for adjusting the distance between the anode (4) and the cathode. The relative positions of the grid (2) and the anode (4) are fixed by means of a positioning small hole on an outer positioning ceramic body and a positioning insulating column (10).

2. An experimental evaluation platform for realizing the open-tube micro X-ray tube as claimed in claim 1, characterized in that: The open-tube micro X-ray tube system is installed on the experimental evaluation platform, which provides the high vacuum environment, acceleration voltage, grid voltage, and filament heating current experimental conditions required by the micro X-ray tube, and receives and evaluates the X-ray signal through the X-ray detector. The experimental platform is a metal cavity with flanges on all six sides. The open-tube micro X-ray tube is fixedly connected through the rear flange, and a high X-ray transmittance sealed window is fixed on the front flange. The X-ray passes through the sealed window and is received by the detector. The left and right flanges are used to connect the vacuum system and the vacuum measurement system. The upper flange is connected to the vacuum high-voltage insulating electrode to provide the anode voltage, and the lower flange cooperates with the X-ray evaluation method and carries the evaluation device.

3. The experimental evaluation platform according to claim 1, characterized in that: The grid (2) is a pencil-shaped structure composed of a hollow truncated cone and a cylinder. A limiting hole is opened at the center of the front front, and a plurality of circular holes around the limiting hole are used to adjust the electric field distribution near the cathode.

4. The experimental evaluation platform according to claim 1, characterized in that: The anode target (5) is a conductive substrate plated with a heavy metal target material.

5. The experimental evaluation platform according to claim 1, characterized in that: The insulator (6) and the positioning insulator (7) are made of polytetrafluoroethylene.

6. The experimental evaluation platform according to claim 1, characterized in that: The anode (5), the insulator (6) and the positioning insulator (7) are provided with positioning holes, which cooperate with the insulating gasket (9) and the positioning insulating column (10) to realize the assembly of the micro X-ray tube and the height adjustment of the anode.

7. The experimental evaluation platform according to claim 1, characterized in that: The vacuum chamber (11) is cylindrical and is provided with flanges at the top, bottom and surrounding areas for connecting to a vacuum pump, a high-voltage electrode and a micro X-ray tube system. The vacuum chamber (11) is made of 304 stainless steel.

8. The experimental evaluation platform according to claim 1, characterized in that: The vacuum high-voltage insulating electrode (12) is an axisymmetric three-layer structure, with a conductive metal electrode in the center, a layer of insulating ceramic on the outside of the electrode, and a metal flange on the outermost side.

9. The experimental evaluation platform according to claim 1, characterized in that: The high X-ray transmittance sealing window (13) is a thin disc with low outgassing rate, made of polypropylene or polytetrafluoroethylene. The high X-ray transmittance sealing window (13) is fixed to the vacuum chamber through a high vacuum flange (14).

10. The experimental evaluation platform according to claim 1, characterized in that: The hot cathode filament (11) is a directly heated pure metal cathode.

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