Micro-focus X-ray source high-power transmission-type multilayer ray conversion target

Abstract

The invention discloses a high-power transmission-type multi-layer ray conversion target of a micro-focus X-ray source. The high-power transmission-type multi-layer ray conversion target comprises a plurality of target layers (1), a plurality of filling layers (2), a substrate (3) and a target supporting body (4), the target layer (1) is used for generating X-rays; the target layer (1) is used for generating X-rays; the target layers (1) and the filling layers (2) alternately grow on the substrate (3); the filling layer (2) is used for conducting heat; the target support body (4) provides support for the target layer (1), and the target support body (4) is mounted on a ray tube. According to the composite target structure of the multi-layer target provided by the invention, electron beams are subjected to energy deposition in the target, can be dispersed into the multi-layer target as far as possible and are taken away by a high-thermal-conductivity material, so that the target temperature is greatly reduced, the target thermal damage is reduced, the target surface power density and the X-ray flux are favorably improved, and an X-ray image with high resolution and high signal-to-noise ratio is favorably obtained.

Description

Technical Field

[0001] The invention relates to the technical field of X-ray sources, in particular to a high-power transmission-type multi-layer ray conversion target for a micro-focus X-ray source. Background Art

[0002] In a microfocus X-ray source, the cathode filament emits an electron beam, which is accelerated by high voltage and focused by an electromagnetic lens before bombarding the ray conversion target.

[0003] High-speed electrons generate bremsstrahlung radiation with target atoms, converting part of the energy into X-rays. However, the efficiency of the bremsstrahlung effect is extremely low, with less than 1% of the electron beam energy converted into X-ray energy, and more than 99% converted into heat energy deposited on the target. Especially in micro-focus X-ray sources, high-power electron beams of several watts to tens of watts bombard the micrometer-scale area on the target surface. If a large amount of heat is not dissipated in time, the high temperature generated will cause ablation damage to the target surface, such as Figure 1 .

[0004] At present, the conventional single-layer X-ray conversion target is severely damaged by high temperature ablation when bombarded by an electron beam with a power of 50W and a half-height width of 10μm for one hour. Figure 2 ; Since the transmission target X-ray converter is usually only a few microns thick, excessively high temperatures will cause the target surface X-ray converter to melt or even evaporate, resulting in a sharp drop in X-ray dose. In more serious cases, it will cause the target to burn through, the X-ray tube to leak, and damage the X-ray tube. Summary of the invention

[0005] The object of the present invention is to provide a micro-focus X-ray source high-power transmission type multi-layer ray conversion target, comprising a plurality of target layers, a plurality of filling layers, a substrate, and a target support body;

[0006] The target layer is used to generate X-rays;

[0007] The target layer and the filling layer are alternately grown on the substrate;

[0008] The filling layer is used for heat conduction;

[0009] The target support body provides support for the target layer, and the target support body is installed on the ray tube.

[0010] Furthermore, the material of the target layer is a high-density, high-temperature resistant material.

[0011] Furthermore, the material of the target layer is tungsten or molybdenum.

[0012] Furthermore, the materials of the filling layer and the substrate are highly conductive materials.

[0013] Furthermore, the material of the filling layer and the substrate is diamond.

[0014] Furthermore, the target support body is made of 316 stainless steel or copper.

[0015] Furthermore, the cross-sectional shapes of the target layer and the filling layer are the same.

[0016] Furthermore, the thickness of the target layer is 1 μm-2 μm, the thickness of the filling layer is 2 μm-10 μm, and the thickness of the substrate is 300 μm-500 μm.

[0017] Furthermore, the target layer, the multiple filling layers and the substrate are all cylindrical.

[0018] The technical effect of the present invention is unquestionable. The present invention provides a composite target structure of a multi-layer target, which enables the energy deposition of the electron beam in the target to be dispersed as much as possible in the multi-layer target and carried away by the high thermal conductivity material. This greatly reduces the target temperature and reduces the thermal damage of the target, which is beneficial to improving the power density and X-ray flux of the target surface, and is beneficial to obtaining high-resolution, high signal-to-noise ratio X-ray images. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a physical picture of target surface damage;

[0020] Figure 2 This is a simulation diagram of target damage;

[0021] Figure 3 It is a high-power transmission-type multi-layer ray conversion target for micro-focus X-ray sources;

[0022] Figure 4 is a transmission target material;

[0023] Figure 5 (a)-(c) are target temperature distributions;

[0024] Figure 6 is the X-ray focus intensity distribution;

[0025] Figure 7 is the X-ray energy spectrum;

[0026] Figure 8 It is an X-ray target structure;

[0027] Fig. 9 (a)-(d) are schematic diagrams of transmission-type multilayer ray conversion targets;

[0028] In the figure, there are target layer 1, filling layer 2, substrate 3 and target support body 4. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0030] Embodiment 1:

[0031] See also Figures 1 to 9 , a micro-focus X-ray source high-power transmission multi-layer ray conversion target, comprising a plurality of target layers 1, a plurality of filling layers 2, a substrate 3, and a target support 4;

[0032] The target layer 1 is used to generate X-rays;

[0033] The target layer 1 and the filling layer 2 are alternately grown on the substrate;

[0034] The filling layer 2 is used for heat conduction to take away the heat of the target layer 1;

[0035] The target support body 4 is used to fix and install the target on the ray tube.

[0036] The target layer 1 is made of a high-density, high-temperature resistant material.

[0037] The target layer 1 is made of tungsten or molybdenum.

[0038] The materials of the filling layer 2 and the base 3 are high-conductivity materials.

[0039] The material of the filling layer 2 and the base 3 is diamond.

[0040] The target support body 4 is made of 316 stainless steel or copper.

[0041] The target layer 1 and the filling layer 2 have the same cross-sectional shape.

[0042] The target layer 1 has a thickness of 1 μm-2 μm, the filling layer 2 has a thickness of 2 μm-10 μm, and the substrate (3) has a thickness of 300 μm-500 μm.

[0043] The target layer 1, the multiple filling layers 2 and the substrate 3 are all cylindrical.

[0044] Embodiment 2:

[0045] A micro-focus X-ray source high-power transmission-type multi-layer ray conversion target comprises a plurality of target layers 1, a plurality of filling layers 2, a substrate 3, and a target support body 4;

[0046] The target layer 1 is used to generate X-rays;

[0047] The target layer 1 and the filling layer 2 are alternately grown on the substrate;

[0048] The filling layer 2 is used for heat conduction.

[0049] The target support body 4 provides support for the target layer 1 and is installed on the ray tube.

[0050] Embodiment 3:

[0051] The micro-focus X-ray source high-power transmission multi-layer ray conversion target has the same technical content as Example 2. Furthermore, the material of the target layer 1 is a dense and high-temperature resistant material.

[0052] Embodiment 4:

[0053] A micro-focus X-ray source high-power transmission-type multi-layer ray conversion target, the technical content of which is the same as any one of Examples 2-3, further, the material of the target layer 1 is tungsten or molybdenum.

[0054] Embodiment 5:

[0055] The micro-focus X-ray source high-power transmission multi-layer ray conversion target has the same technical content as any one of Examples 2-4, and further, the materials of the filling layer 2 and the substrate 3 are high-conductivity materials.

[0056] Embodiment 6:

[0057] A micro-focus X-ray source high-power transmission multi-layer ray conversion target, the technical content of which is the same as any one of Examples 2-5, and further, the material of the filling layer 2 and the substrate 3 is diamond.

[0058] Embodiment 7:

[0059] The micro-focus X-ray source high-power transmission multi-layer ray conversion target has the same technical content as any one of Examples 2-6, and further, the material of the target support body 4 is 316 stainless steel or copper.

[0060] Embodiment 8:

[0061] A micro-focus X-ray source high-power transmission-type multi-layer ray conversion target, the technical content of which is the same as any one of Examples 2-7, and further, the cross-sectional shapes of the target layer 1 and the filling layer 2 are the same.

[0062] Embodiment 9:

[0063] A micro-focus X-ray source high-power transmission multilayer ray conversion target, the technical content of which is the same as any one of Examples 2-8, further, the thickness of the target layer 1 is 1μm-2μm, the thickness of the filling layer 2 is 2μm-10μm, and the thickness of the substrate 3 is 300μm-500μm.

[0064] Embodiment 10:

[0065] A micro-focus X-ray source high-power transmission-type multi-layer ray conversion target, the technical content of which is the same as any one of Examples 2-9, further, the target layer 1, the multiple filling layers 2, and the substrate 3 are all cylindrical.

[0066] Embodiment 11:

[0067] The micro-focus X-ray source high-power transmission multi-layer ray conversion target includes a ray converter-target layer made of dense high-temperature resistant materials (tungsten, molybdenum), a filling layer using high-conductivity materials (diamond) for heat conduction and support, a diamond substrate, and a target support body (316 stainless steel, copper) for supporting the entire structure.

[0068] The present invention designs a transmission target structure composed of multiple layers of targets, which can disperse the energy deposition in the target when the electron beam bombards the target, reduce the energy density in the target, and improve the heat dissipation capacity of the target, thereby greatly reducing the maximum temperature of the target and the risk of thermal damage to the target. It can further greatly increase the maximum target power of the target or reduce the size of the X-ray focus, which is conducive to obtaining high signal-to-noise ratio and high-resolution X-ray images.

[0069] The present invention designs a multi-layer X-ray target surface so that the energy deposition in a single-layer target is dispersed into the multi-layer target to reduce the concentration of heat. At the same time, a high thermal conductivity layer is filled between each layer of the target to quickly remove the heat in the target. The target layer and the thermal conductive layer are alternately plated on the substrate in sequence by using a coating method such as magnetron sputtering, so that the target has good thermal conductivity and heat resistance, and also avoids excessive reduction in X-ray yield. The specific structure is as follows Figure 3 shown.

[0070] Figure 3 In the figure, 1 is a target layer (sequentially W1, W2, W3, W4...) for generating X-rays, 2 is a filling layer (sequentially D1, D2, D3...) for conducting heat and separating the target layer, 3 is a substrate for supporting the target layer and the filling layer, and 4 is for supporting the entire target structure.

[0071] The multi-layer target structure can quickly disperse the energy deposition in the target, thereby reducing the average power density of the target and improving the heat dissipation capacity of the target, so that the radiation target can increase the upper limit of the target power and reduce the X-ray focus.

[0072] Transmission X-ray target surfaces usually use high atomic number, high density and high temperature resistant metals such as tungsten and molybdenum. The substrate is usually a high thermal conductivity material such as diamond. The present invention divides the tungsten target surface that generates X-rays into multiple layers, and uses diamond to fill the intervals between each layer. The target layer and the filling layer are simultaneously plated on the diamond substrate. The structure is as follows: Figure 4 shown.

[0073] Use COMSOL to simulate the temperature of the target. Figure 5 (a) is the temperature simulation result of a single-layer target, with the setting parameters of 225kV tube voltage, 10μm electron beam half-height width, and 35W target power. It can be found that the energy deposition in tungsten is highly concentrated, and the maximum target temperature is 1750degC.

[0074] Figure 5(b) is the temperature simulation result of the 7-7-7 multilayer target proposed in the present invention (the filling layer combination is 7-7-7, the thicknesses of D1, D2, and D3 are respectively, the target layer has 4 layers, each layer is 1, unit: μm), the parameters are Figure 5 (a) is the same, the maximum temperature of the target drops to 810degC, a decrease of 940degC, a decrease of 53.71%. Figure 5 (c) is the temperature distribution at the same maximum target temperature. When the maximum temperature is the same as that of the single-layer target, the maximum target power can reach 77.5 W, an increase of 42.5 W, or 170%.

[0075] In order to explore the influence of multi-layer target design on X-ray focus, X-ray yield and energy spectrum, EGS was used to simulate the X-ray focus size and X-ray yield of multi-layer targets and single-layer targets. Figure 6 To simulate the X-ray focus intensity distribution obtained by edge method, for an electron beam with a diameter of 10μm at 225kV, the X-ray focus size of the single-layer target is 13.23μm, and that of the multi-layer target 7-7-7 is 15.89μm, which is 20.11% larger. This is because the design of the multi-layer target causes more serious lateral diffusion of electrons in the target. Figure 8 The energy spectrum distribution of X-rays is basically the same for the single-layer target and the multi-layer target 7-7-7. As for the X-ray yield, it dropped from 1.545% to 1.500%, a decrease of 2.91%. The energy spectrum is highly consistent, so in order to link the focus, target power, and X-ray yield, the X-ray power density is defined: X-ray power density = X-ray yield × maximum target power / X-ray focus, unit: W / μm; then the X-ray power density is increased from 4.09E-2W / μm to 7.32E-2W / μm, an increase of 78.97%.

[0076] At the same time, the target performance under low energy conditions is also simulated. For 100kV tube voltage, 10μm diameter electron beam, 25W single-layer target power, and multi-layer target 7-7-7, the maximum target power is increased to 72.6W, an increase of 190.4%; the X-ray focus is expanded from 13.02μm to 14.41μm, an increase of 10.68%; although the target power is increased at a greater rate, the performance of the X-ray is seriously changed, and the X-ray energy spectrum changes significantly, such as Figure 7 At the same time, the X-ray yield also dropped significantly, from 0.914% to 0.521%, a decrease of 43%. The X-ray power density increased from 1.75E-2W / μm to 2.62E-2W / μm, an increase of 49.71%.

[0077] In general, compared with a single-layer target, the multi-layer target design can significantly increase the maximum target power while sacrificing only a small part of the X-ray performance. Specifically, at a tube voltage of 225kV and a 10μm diameter electron beam, the maximum target power increased from 35W to 77.5W, an increase of 170%; the X-ray focus expanded from 13.23μm to 15.89μm, an increase of 20.11%; the X-ray yield decreased from 1.55% to 1.54%, a decrease of 6.45%. The X-ray power density increased from 4.09E-2W / μm to 7.32E-2W / μm, an increase of 78.97%.

[0078] The present invention describes a design structure of a multi-layer target transmission X-ray target. This scheme divides a single-layer target into multiple layers and fills a high thermal conductivity layer between them, thereby dispersing the energy deposition in the target and improving the heat resistance and thermal conductivity of the target. Figure 8 shown.

Claims

1. Micro-focus X-ray source high power transmission type multi-layer ray conversion target, characterized by: It comprises a plurality of target layers (1), a plurality of filling layers (2), a substrate (3), and the target support body (4); The target layer (1) is used to generate X-rays. The target layer (1) and the filling layer (2) are alternately grown on the substrate (3); The filling layer (2) is used for heat conduction; The target support body (4) provides support for the target layer (1), and the target support body (4) is installed on the ray tube.

2. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The material of the target layer (1) is a high-density, high-temperature resistant material.

3. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 2, characterized in that: The target layer (1) is made of tungsten or molybdenum.

4. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The materials of the filling layer (2) and the base (3) are highly conductive materials.

5. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 4, characterized in that: The materials of the filling layer (2) and the base (3) are diamond.

6. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The target support body (4) is made of 316 stainless steel and copper.

7. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The target layer (1) and the filling layer (2) have the same cross-sectional shape.

8. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The target layer (1) has a thickness of 1 μm-2 μm, the filling layer (2) has a thickness of 2 μm-10 μm, and the substrate (3) has a thickness of 300 μm-500 μm.

9. The micro-focus X-ray source high-power transmission-type multi-layer ray conversion target according to claim 1, characterized in that: The target layer (1), the plurality of filling layers (2) and the substrate (3) are all cylindrical.

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