Field emission x-ray source

Abstract

The utility model relates to spectrum technology, specifically provide field emission X -ray source, including field emission effect cathode, target material, anode and pull out pole, the target material sets up on the anode, still include electron focusing unit, including shell, superconducting coil and refrigeration module, the superconducting coil sets up in the shell, the refrigerant that refrigeration module provides enters the shell through first pipeline, and returns to refrigeration module through second pipeline, the cathode, pull out pole, superconducting coil and anode set gradually, pull out pole adopts the grid net structure. The utility model has the advantages such as high brightness, focusing stable etc.

Description

Technical Field

[0001] This utility model relates to spectroscopy technology, and in particular to field emission X-ray sources. Background Technology

[0002] X-rays are generated by bombarding materials with high atomic numbers with high-energy electrons. The smaller the electron spot on the material surface, the smaller the resulting X-ray source spot. Small-spot X-ray sources have important applications in high-resolution imaging, micro-area analysis, and non-destructive testing.

[0003] Existing X-ray source technology uses tungsten filament electron emission systems and electrostatic lenses or ordinary coil lenses for focusing. However, electrostatic lenses have weak focusing ability and the focused spot is large under high accelerating voltage. Magnetic lenses have strong focusing ability, but ordinary magnetic lenses have low strength due to size constraints and limited focusing ability, making it impossible to focus high-energy electrons into a smaller beam.

[0004] To obtain a small electron focusing spot, a relatively small electron source is also required. Among many electron guns, the field emission electron gun has a relatively small light source size. The pull-out electrode of the field emission electron gun can increase the electric field strength of the tip of the field emission power supply, thereby greatly increasing the emission current of the field emission source. However, the pull-out electrode itself will block most of the electrons, thus preventing the electrons from being utilized with maximum efficiency. Summary of the Invention

[0005] To address the shortcomings of the existing technical solutions, this utility model provides a field emission X-ray source.

[0006] The objective of this utility model is achieved through the following technical solution: A field emission X-ray source includes a field emission cathode, a target, an anode, and a pull-out electrode, wherein the target is disposed on the anode; the X-ray source further includes: An electron focusing unit includes a housing, a superconducting coil, and a cooling module. The superconducting coil is disposed inside the housing. The refrigerant supplied by the cooling module enters the housing through a first pipe and returns to the cooling module through a second pipe. The cathode, pull-out electrode, superconducting coil, and anode are arranged in sequence. The pull-out pole adopts a grid structure.

[0007] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. By using a field emission electron source instead of a tungsten filament electron source, the size of the electron source is reduced, allowing for a smaller beam spot after focusing by the magnetic lens; 2. Using a grid-like pull-out electrode instead of a round hole pull-out electrode increases electron transmittance, thereby enhancing the brightness of the X-ray source; 3. Using superconducting coils reduces the size of the magnetic lens while increasing its strength, thereby reducing the focal length of electron focusing. This results in a smaller beam spot, a more compact structure, and a smaller overall size. Furthermore, the current generated by the superconducting coils is almost ripple-free, ensuring stable electron beam focusing. Attached Figure Description

[0008] The disclosure of this utility model will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this utility model and are not intended to limit the scope of protection of this utility model. In the drawings: Figure 1 This is a schematic diagram of the X-ray source according to Embodiment 1 of this utility model; Figure 2 This is a schematic diagram of the electronic focusing unit according to the present invention; Figure 3 This is a schematic diagram of the pull-out electrode in Embodiment 1 of this utility model; Figure 4 This is a schematic diagram of the pull-out electrode in Embodiment 2 of this utility model; Figure 5 This is a schematic diagram of the pull-out electrode in Embodiment 3 of this utility model; Figure 6 This is a schematic diagram of the X-ray source structure in Embodiment 2 of this utility model; Figure 7 This is a schematic diagram of the structure of the X-ray source according to Embodiment 3 of this utility model.

[0009] In the attached diagram, 100 is the field emission cathode, 101 is the grid, 102 is the pull-out electrode, 103 is the electron focusing unit, 104 is the cooling module, 105 is the target material, 106 is the anode, 107 is the transmission window, 108 is the first power supply, 109 is the second power supply, 110 is the third power supply, 201 is the outer casing, 202 is the superconducting coil, 203 is the refrigerant, and 301 is the grid structure. Detailed Implementation

[0010] Figures 1-7 The following description illustrates optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce it. For the purpose of teaching the technical solutions of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Therefore, the present invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0011] Example 1

[0012] One type of field emission X-ray source in this embodiment, such as Figure 1 As shown, it includes: The field emission cathode 100, target 105, anode 106, and pull-out electrode 102 are provided, wherein the target 105 is disposed on the anode 106.

[0013] The gate 101 has a through hole with a diameter of 400 μm. The tip of the cathode 100 passes through the through hole and extends for a length of 300 μm. The distance between the tip and the pull-out electrode 102 is 500 μm-1000 μm.

[0014] The first power supply 108 applies a voltage between the cathode 100 and the anode 106, with the voltage to the cathode 100 being 50 kV - 200 kV.

[0015] The third power supply 110 applies a voltage between the cathode 100 and the grid 101. A negative voltage is applied to the grid 101 to the cathode to control the electron emission angle. The negative voltage is adjustable between -100V and -400V.

[0016] The second power supply 109 applies a voltage between the cathode 100 and the pull-out electrode 102. A positive voltage of 3kV to 5kV is applied to the pull-out electrode 102 to the cathode 100 to increase the electric field strength of the cathode 100. The voltage at the pull-out electrode 102 can make the electric field strength at the tip of the cathode 100 greater than 5×10^8V / m, and the emitted electron current greater than 100μA.

[0017] like Figure 2 As shown, the electron focusing unit 103 includes a housing 201, a superconducting coil 202, and a cooling module 104. The superconducting coil 202 is disposed inside the housing 201, has 5-10 turns, a diameter of 10mm-20mm, and can carry a current of over 1000A. The refrigerant 203 supplied by the cooling module 104 enters the housing 201 through a first pipe and returns to the cooling module 104 through a second pipe. The cathode 10, the pull-out electrode 102, the superconducting coil 202, and the anode 106 are arranged sequentially.

[0018] like Figure 3 As shown, the pull-out electrode 102 adopts a honeycomb grid structure 301. The grid is made of 10μm thick metal wires and has a polygonal structure with a regular hexagonal side length of 100μm, which is used to improve the electron throughput.

[0019] The cathode 100 and the pull-out electrode 102 are disposed inside the housing, and the transmission window 107 (made of beryllium, carbon, glass or aluminum) is disposed on the housing to allow X-rays to pass through.

[0020] During operation, electrons emitted from the cathode 100 pass through the pull-out electrode 102, then through the superconducting coil 202, and are focused onto the target material 105. The generated X-rays are strongest in the direction of the transmission window due to the inclined anode surface, and most of the X-rays pass through the transmission window 107.

[0021] Example 2

[0022] The application example of the X-ray source according to Embodiment 1 of this utility model differs from Embodiment 1 in that: like Figure 4 As shown, the electron emission intensity of the cathode exhibits a Gaussian distribution, with stronger electron intensity at the center. Therefore, the grid structure at the center of the cathode is eliminated and replaced with a circular through-hole structure to further reduce the obstruction of electrons.

[0023] Example 3

[0024] The application example of the X-ray source according to Embodiment 1 of this utility model differs from Embodiment 1 in that: like Figure 5 As shown, a highly linear orthogonal grid structure is drawn out, with a gridless circle at the center.

[0025] Example 4

[0026] The application example of the X-ray source according to Embodiment 1 of this utility model differs from Embodiment 1 in that: like Figure 6 As shown, the anode and the transmission window 107 (made of beryllium) are shared, and the X-rays emitted from the target 105 pass through the target 105 and the transmission window 107 in sequence.

[0027] The outer casing 201 is disposed within the housing and surrounds the transmission window 107.

[0028] The superconducting coil 202 is placed horizontally at the same level as the target 105. The current flowing through the coil 202 is 1000A-2000A. At this time, high-energy electrons will focus near the center of the superconducting coil 202 and bombard the target 105 to generate X-rays. The overall structure volume is further reduced. The X-ray beam spot is less than 1μm, and the volume of the X-ray source system is less than 3cm×3cm×5cm.

[0029] Example 5

[0030] The application example of the X-ray source according to Embodiment 1 of this utility model differs from Embodiment 4 in that: like Figure 7 As shown, the outer casing 201 is disposed outside the housing and surrounds the transmission window.

[0031] The superconducting coil 202 is placed outside the X-ray source housing, flush with the transmission window 107. The superconducting coil 202 is placed in the air, eliminating the need for the cooling pipe interface of the X-ray source, making the internal vacuum structure of the X-ray source simpler and easier to manufacture, and also making the debugging of the superconducting coil 202 more convenient.

Claims

1. A field emission X-ray source, comprising a field emission cathode, a target, an anode, and a pull-out electrode, wherein the target is disposed on the anode; characterized in that, The X-ray source also includes: An electron focusing unit includes a housing, a superconducting coil, and a cooling module. The superconducting coil is disposed inside the housing. The refrigerant supplied by the cooling module enters the housing through a first pipe and returns to the cooling module through a second pipe. The cathode, pull-out electrode, superconducting coil, and anode are arranged in sequence. The pull-out pole adopts a grid structure.

2. The X-ray source according to claim 1, characterized in that, The X-ray source also includes: The housing and transmission window are provided, with the cathode and pull-out electrode disposed inside the housing and the transmission window disposed on the housing to allow X-rays to pass through.

3. The X-ray source according to claim 2, characterized in that, The X-rays emitted from the target are reflected by the anode and pass through the transmission window.

4. The X-ray source according to claim 2, characterized in that, The anode and the transmission window are shared, and the X-rays emitted from the target material pass through the target material and the transmission window in sequence; The outer casing is disposed inside or outside the housing, surrounding the transmission window.

5. The X-ray source according to claim 4, characterized in that, The material of the transmission window is beryllium.

6. The X-ray source according to claim 1, characterized in that, The X-ray source also includes: A gate having a through-hole through which the tip of the cathode passes; A power source that applies a voltage between the cathode and the anode, a voltage between the cathode and the grid, and a voltage between the cathode and the pull-out electrode.

7. The X-ray source according to claim 6, characterized in that, The distance between the tip and the pull-out electrode is 500μm-1000μm.

8. The X-ray source according to claim 1, characterized in that, The extracted part is either a honeycomb structure or a linear orthogonal grid structure.

9. The X-ray source according to claim 8, characterized in that, The center of the pull-out electrode is circular.

10. The X-ray source according to claim 1, characterized in that, The coil has 5-10 turns and a diameter of 10mm-20mm.

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