A neutron generating target

Abstract

The present invention relates to the technical field of accelerator-driven target bodies, and in particular to a high-power neutron generation target for accelerator drive with efficient cooling function and temperature and beam spot monitoring function; the neutron generation target comprises a target material layer, a particle migration layer, a microchannel substrate layer and a cover plate layer which are sequentially bonded and connected to form an integrated multi-layer structure target body, and a plurality of groups of thermocouple assemblies are arranged on the target body; a plurality of rows of fins are processed on the surface of the microchannel substrate layer, and tiny heat dissipation channels are formed between adjacent fins; the present invention solves the problem that an infrared imaging camera cannot work for a long time in a high-dose radiation environment around the target body; the neutron generation target is cooled by using a tiny heat dissipation channel structure, which is beneficial to the prediction of the proton beam spot shape and the temperature monitoring of the target material; the thermocouples are uniformly distributed and are at the same distance from the target material surface, so as to form a uniformly measured temperature field, which is beneficial to the prediction of the beam spot shape.

Description

Technical Field

[0001] The present invention relates to the technical field of accelerator-driven target generation, and in particular to a high-power neutron generation target for accelerator-driven neutron generation with high-efficiency cooling function and temperature and beam spot monitoring function. Background Art

[0002] When particles or rays generated by an accelerator bombard neutron-generating targets, especially low-energy protons, high unit heat flux density and high heat load power, such as the boron neutron capture therapy for cancer, protons are used as incident particles, the proton energy is between 2MeV and 10MeV, the proton beam power is as high as 30kW or more, and the proton range in the metal is short, and the heat flux density exceeds 100kW / cm2. Due to the low proton range, the proton irradiated beam measurement element will be deposited in the beam measurement element and cause it to burn, so it is difficult to obtain a specific beam spot distribution; in addition, when the proton beam power is high and the distribution is concentrated, the heat flux density is high. If low-melting-point materials are used as targets, such as lithium targets, whose melting point is only 180 degrees Celsius, the heat removal problem of lithium targets is large, so it is necessary to monitor the temperature operation of the target in real time to ensure uniform irradiation of the proton beam spot and avoid melting of the lithium layer and damage to the target.

[0003] The neutron generation target provided by the patent invention of CN106385757A detects the temperature of each point on the target body through a temperature sensor, including thermocouple thermometers for detecting the incident surface of the target body, the edge of the incident surface of the target body, the vicinity of the connection between the target body and the cooling seat, and the cavity pipeline. Multiple groups of thermometers jointly complete the temperature and beam spot monitoring. In addition, the interior of the cooling seat is an independent cavity, which is not connected to the vacuum cavity of the target body. The target body is isolated from the cooling water, and the target body cooling function is realized through the heat sink in the cooling seat at the bottom of the target body and the connected cooling water pipe. However, there are the following problems: First, the temperature measuring wire of the thermocouple in the above scheme is led out from the vacuum side and needs to be led out through a vacuum wall-penetrating piece, which is difficult to arrange, and the arrangement of thermocouples at multiple different positions makes installation difficult; Second, under high beam power conditions, the leads or thermocouples of the temperature measuring element deep in the center of the beam will be directly irradiated by the beam, resulting in excessive temperature and burning; Third, the temperature measuring element is deep in the center of the beam in a vacuum, and the beam directly irradiates the temperature measuring element rather than the target, resulting in a decrease in neutron yield; Fourth, the temperature measuring element directly penetrates into the cooling seat from all sides, destroying its cooling structure and reducing the heat exchange effect, while limiting the number of measurement points, resulting in an inaccurate response to the beam spot distribution. Summary of the invention

[0004] In view of the above-mentioned deficiencies, the present invention aims to provide a neutron production target, including a device for producing neutrons by irradiating a neutron target with particles such as protons and heavy ions or rays, and in particular, a high-power neutron production target for accelerator drive with efficient cooling function and temperature and beam spot monitoring function.

[0005] The technical solution adopted by the present invention is: a neutron generation target, which includes a target material layer, a particle migration layer, a microchannel base layer and a cover layer that are sequentially bonded and connected to form an integrated multi-layer structure target body, and multiple groups of thermocouple assemblies are arranged on the target body; the surface of the microchannel base layer is processed with multiple rows of fins, and tiny heat dissipation channels are formed between adjacent fins.

[0006] The thermocouple components are evenly distributed on the target structure, penetrating the target from the cover layer until they are close to the target material layer.

[0007] The thermocouple assembly comprises a thermocouple and a sleeve. The sleeve penetrates the target body from the cover plate layer until it is close to the target material layer. The thermocouple is inserted into the corresponding sleeve to get as close to the target material as possible and infer the target material temperature.

[0008] The thermocouple penetrates the target cover plate layer and the surface fins of the microchannel substrate layer and reaches the bottom of the microchannel substrate layer.

[0009] The bottom surface of the cover plate layer is bonded to the microchannel base layer, and the cover plate layer is sealed by welding or threaded fastening to surround the microchannel base layer at the bottom and form a cavity structure with the microchannel base layer.

[0010] The two ends of the cavity are provided with an inlet and an outlet for the cooling medium, and an expansion area is provided between the inlet and the outlet and the microchannel structure so that the flow rate of the fluid in and out of each channel is equal or close, thereby achieving uniform heat exchange.

[0011] The upper surface of the microchannel substrate layer is bonded and connected to the cover plate layer, and the lower surface is bonded and connected to the particle migration layer by diffusion welding or coating.

[0012] The height dimensions of the particle migration layer and the target material layer are lower than the dimension of the central cooling area of ​​the microchannel substrate layer.

[0013] Each row of fins is arranged at equal distances, and the fins are made of heat exchange materials such as copper, aluminum, nickel, iron or their alloys, graphite, and heat-conducting graphite sheets.

[0014] The working medium inlet and outlet of the microchannel substrate layer are expanded in combination with the micro heat dissipation channels, so that the flow distribution inside each micro heat dissipation channel is the same or close.

[0015] The target material layer uses one of lithium, carbon, beryllium, aluminum and tungsten as a raw material.

[0016] When the target layer uses aluminum as the raw material, no or less neutrons are generated and the residual radioactive elements are less as a debugging target.

[0017] The beneficial effects of the present invention are as follows: in the present invention, an inserted thermocouple assembly is used to replace the infrared imaging camera to measure the temperature of the target material, thereby solving the problem that the infrared imaging camera cannot work for a long time in a high-dose radiation environment around the target body; a micro heat dissipation channel structure is used to cool the neutron generation target, and the fins are made of heat exchange materials such as copper, aluminum, and its alloys or graphite, so that the heat removal efficiency is high; a micro heat dissipation channel is used in combination with the inlet and outlet of the micro heat dissipation channel to perform an expansion design, so that the flow distribution inside each microchannel is the same or close, so that the heat removal capacity of the microchannel is evenly distributed, which is conducive to the prediction of the proton beam spot shape; the thermocouple assembly is covered by the target body The plate layer and the fins on the surface of the microchannel base layer penetrate into the bottom of the microchannel base layer so as to be as close to the target material layer as possible to realize temperature monitoring of the target material, while avoiding the influence on the heat exchange structure and avoiding direct irradiation of particles when measuring the target material through vacuum; the drilling depth in the microchannel base layer is consistent and evenly distributed, which is conducive to processing and installation; evenly distributed thermocouples are used, and their distance from the target surface is consistent, so as to form a uniformly measured temperature field, which is conducive to the prediction of the beam spot shape, and convex structures can be evenly arranged at the center position of each heat exchange flow channel formed between the fins along the flow direction of the cooling medium, and they are all of the same height. The convex structure can increase disturbance and enhance the heat exchange effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the decomposition structure of the present invention.

[0020] Figure 3 It is a side view structural schematic diagram of the present invention.

[0021] Figure 4 It is a schematic diagram of the longitudinal cross-section structure of the middle part of the present invention.

[0022] Figure 5 It is a schematic diagram of the transverse cross-sectional structure of the middle part of the present invention.

[0023] Figure 6 It is a schematic diagram of the structure of the microchannel substrate layer in Example 1 of the present invention.

[0024] Figure 7 It is a schematic diagram of the structure of the microchannel substrate layer in the second embodiment of the present invention.

[0025] Description of the accompanying drawings: 1-target material layer, 2-particle migration layer, 3-microchannel base layer, 4-cover layer, 5-thermocouple assembly, 31-fin, 32-outlet, 33-inlet, 34-protrusion structure. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings:

[0027] like Figure 1-5 As shown, a neutron generation target comprises a target material layer 1, a particle migration layer 2, a microchannel substrate layer 3 and a cover layer 4 which are sequentially bonded and connected to form an integrated multi-layer structure target body, on which a plurality of groups of thermocouple assemblies 5 are arranged; the surface of the microchannel substrate layer 3 is processed with a plurality of rows of fins 31, and tiny heat dissipation channels, referred to as microchannels, are formed between adjacent fins 31.

[0028] In the present invention, the neutron generation target detects the temperature of each point on the target body through the inserted thermocouple assembly 5, and uses the temperature value of each point on the target body layer to infer whether the target material temperature exceeds the limit, thereby realizing real-time temperature monitoring and avoiding target operation accidents.

[0029] In the present invention, the temperature values ​​of multiple evenly distributed thermocouple assemblies 5 are used to judge the beam spot shape, thereby realizing the beam spot monitoring function; wherein the sleeve in the thermocouple assembly 5 is connected through the cover layer 4, the microchannel base layer 3, the particle migration layer 2 and the target material layer 1, and the thermocouple is inserted into the corresponding sleeve to get as close to the target material as possible and infer the target material temperature.

[0030] In the present invention, the cover layer 4 is sealed by welding or threaded fastening to surround the microchannel substrate layer 3 at the bottom and form a cavity structure. The surface of the microchannel substrate layer 3 is processed with multiple rows of equidistantly arranged fins 31, and tiny heat dissipation channels are formed between adjacent fins 31. The two ends of the cavity are provided with an inlet 33 and an outlet 32 ​​for the cooling medium. There is an expansion domain between the inlet 33 and the outlet 32 ​​and the microchannel structure so that the flow rate of the fluid in and out of each channel is equal or close to form a uniform heat exchange. The microchannel substrate layer 3 is connected to the particle migration layer 2, and the particle migration layer 2 is connected to the target material layer 1, and the size of the particle migration layer 2 and the target material layer 1 is smaller than the size of the central cooling area of ​​the microchannel substrate.

[0031] When the beam spot irradiates the target material, the neutron damage energy generated in the target material is partial, and the whole energy is damaged in the particle migration layer 2. At the same time, a large amount of energy deposited in the particle migration layer 2 is transferred to the microchannel substrate layer 3 in a heat conduction manner. Therefore, the tightly connected microchannel substrate layer 3 is used for efficient heat deposition removal. The cooling medium expands the flow cross section from the inlet 33 and flows evenly through each channel of the microchannel. During this period, the heat dissipation channel structure evenly distributed on the surface of the substrate forms a uniform distribution effect on the medium, and further increases the heat exchange area through the microchannel, thereby increasing the heat exchange capacity of the medium. Finally, the cooling medium of each heat dissipation channel is collected at the outlet 32 ​​on the other side and discharged.

[0032] At this time, the principle of judging the shape of the beam spot on the target surface is: a uniformly distributed heat exchange structure is formed through microchannels, and the thermocouple enters the target through the cover layer 4 at the rear of the target to measure the temperature to avoid, reduce or form consistent temperature differences; when the beam spot is evenly distributed, the heat exchange structure and thermal resistance are the same for the thermocouples, and the temperature values ​​of each thermocouple remain consistent; and when the beam deflection occurs, the beam spot deflection will cause the overall migration of the thermocouple temperature value. When the beam is unevenly focused locally, the temperature of the area where the beam is focused is higher. Therefore, the direction of beam deviation and beam focusing can be judged by comparing the thermocouple temperature values ​​on the target surface, and the degree of beam deviation and focusing can be inferred by detecting the thermocouple temperature value at the center of the target surface, and multiple thermocouples can be used to jointly infer the real-time situation of the beam spot on the target surface.

[0033] In the present invention, an inserted thermocouple assembly 5 is used to replace the infrared imaging camera to measure the temperature of the target material, which solves the problem that the infrared imaging camera cannot work for a long time in the high-dose radiation environment around the target body; the neutron generation target is cooled by using a micro heat dissipation channel structure, and the fins 31 are made of heat exchange materials such as copper, aluminum, and its alloys or graphite, and the heat removal efficiency is high; the micro heat dissipation channel is combined with the inlet and outlet 33 of the micro heat dissipation channel for expansion design, so that the flow distribution inside each microchannel is the same or close, so that the heat removal capacity of the microchannel is evenly distributed, which is conducive to the prediction of the proton beam spot shape; the thermocouple assembly 5 penetrates into the bottom of the microchannel substrate through the target cover layer 4 and the fins 31 on the surface of the microchannel substrate layer 3, so as to be as close to the target material layer 1 as possible, realize the temperature monitoring of the target material, and avoid the influence on the heat exchange structure, and avoid direct irradiation of particles when measuring the target material through vacuum; the drilling depth in the microchannel substrate layer 3 is consistent and evenly distributed, which is conducive to processing and installation; evenly distributed thermocouples are used, and their distance from the target surface is consistent, so as to form a uniformly measured temperature field, which is conducive to the prediction of the beam spot shape.

[0034] Embodiment 1: lithium is used as the target material layer 1, wherein the target fins 31 have the same height, specifically 3 mm, with a spacing of 1 mm and a width of 1 mm; the inlet and outlet 32 ​​are semicircular structures with a diameter of 40 mm, and the spacing around the thermocouple is 20 mm.

[0035] like Figure 1-6 As shown, a neutron generation target comprises a target material layer 1, a particle migration layer 2, a microchannel substrate layer 3 and a cover layer 4 which are sequentially bonded and connected to form an integrated multi-layer structure target body. The cover layer 4 seals and surrounds the microchannel substrate layer 3 at the bottom by welding or threaded fastening to form a cavity structure. An inlet 33 and an outlet 32 ​​for the flow of cooling medium are provided at both ends of the cavity structure to ensure the mechanical strength of the connection.

[0036] Among them, the microchannel base layer 3 is used to cool the target material layer 1. The surface of the microchannel base layer 3 is processed with multiple rows of fins 31, and tiny heat dissipation channels are formed between adjacent fins 31. The cavity structure is used to accommodate the fin 31 structure. Multiple groups of thermocouple assemblies 5 are arranged on the target body to monitor the surface temperature of the target material.

[0037] The thermocouple assembly 5 is evenly distributed on the target structure, penetrating the target from the cover layer 4 until close to the target layer 1. The microchannel base layer 3 and the cover layer 4 are uniformly drilled, and a sleeve with one end sealed is inserted into the corresponding drilled hole, and fastened by welding or threading. Then, the thermocouple is inserted into the bottom of each sleeve to get as close as possible to measure the temperature of the target layer 1. The drilled holes are evenly distributed in a square shape, totaling 25; one end of the sleeve is a sealed structure to ensure that the sealed cooling water does not leak through the sleeve; the external connector of the thermocouple leads the signal through the rear end of the sleeve and enters the measurement system.

[0038] The cover layer 4 is sealed and surrounded by the microchannel base layer 3 by welding or threaded fastening to form a cavity structure. The surface of the microchannel base is processed with multiple rows of equidistant fins 31. The spacing between adjacent fins 31 is equal to form equidistant tiny heat dissipation channels, and the channels have the same length along the flow direction; the left and right ends of the cavity are provided with an inlet 33 and an outlet 32 ​​for the cooling medium, wherein the inlet 33 and the outlet 32 ​​are flared and connected to the cavity microchannel structure, the microchannel base layer 3 is diffusion welded to the bottom of the particle migration layer 2, and when lithium is used as the target material, it is connected to the particle migration layer 2 by coating, and the particle migration layer 2 is connected to the microchannel structure by diffusion welding; wherein the size of the central cooling area of ​​the microchannel base layer 3 is larger than the size of the proton beam spot and the particle migration layer 2.

[0039] In this embodiment, under high power conditions, the efficient cooling and heat exchange of the microchannel helps to reduce the target temperature and improve the heat removal capacity. In particular, when a low-melting point target such as a lithium target is used under high power conditions, the melting of lithium and damage to the target can be avoided by real-time monitoring of temperature and beam spot. At the same time, the microchannel technology is used to effectively cool the target under the high heat flux density generated when particles bombard the neutron-generating target, and the energy deposition of the target is removed in time. It is proposed to set up a bottom-sealed straight tube on the back cover layer 4 of the target to pass through the fin 31 of the microchannel to measure the temperature near the target surface, so as to avoid the influence of the blockage in the channel and have less influence on the cooling structure. In the implementation process, a temperature measuring element is arranged through the fin 31 of the microchannel on the back of the neutron generating target to measure the temperature close to the target material, which is closer to the actual temperature of the target material. The uniform microchannel structure and the uniformly distributed cooling medium inside the microchannel provide uniform cooling capacity for the target, and combined with the uniform matrix-type temperature measuring element arrangement, the feedback of the beam spot distribution on the surface of the neutron generating target is realized through the temperature distribution, which provides a reference for the accelerator beam adjustment.

[0040] Embodiment 2: lithium oxide is used as the target material layer 1 , wherein the target fins 31 have the same height, specifically 5 mm, a length of 120 mm, a width of 2 mm, and a spacing of 2 mm between each fin 31 .

[0041] The difference between the second embodiment and the first embodiment is that the first embodiment uses lithium as the target material, which has a low melting point. Even if the microchannel technology is used to dissipate heat to a certain extent, it is inevitable that the target temperature will be too high, resulting in the melting of lithium. In addition, the heat dissipation technology in the first embodiment uses a conventional microchannel structure. When extreme conditions occur, such as a high degree of beam concentration, its heat dissipation effect may not achieve the ideal effect. Figure 7 In the second embodiment shown, lithium oxide is used as the target material layer 1, wherein the target body fins 31 are of equal height, specifically 5 mm, 120 mm in length, 2 mm in width, and the spacing between each fin 31 is 2 mm; a protrusion structure 34 is provided at the center position of each heat exchange channel formed between the fins 31 along the flow direction of the cooling medium, and the protrusion structure is "blade-shaped" and is evenly distributed between every two fins 31. In this embodiment, six "blade-shaped" protrusion structures 34 of equal height are evenly distributed, and the equal height can ensure assemblability and sealing. The protrusion structure 34 can increase disturbance and enhance the heat exchange effect, specifically 1 mm, and the spacing between two adjacent protrusion structures 34 is 20 mm.

[0042] In the second embodiment, lithium oxide is used as the target material. The feasibility of replacing lithium with this material is demonstrated in the literature of "AB-BNCT Neutron Target Physical Design Analysis". Although the neutron yield is reduced compared with lithium, the reduction is not large and the melting point is significantly increased from 180°C to 1567°C, which fully improves the heat resistance of the target material and ensures the safe operation of the target body at high temperatures. In addition, by evenly arranging the "blade-type" protruding structure in the microchannel to increase the flow rate of the cooling medium and the turbulent intensity of the flow, the overall heat exchange effect of the microchannel is further enhanced to meet the heat dissipation requirements under special working conditions.

[0043] The present invention can use one of lithium, carbon, beryllium, aluminum, and tungsten as the target material, among which when aluminum is used, no or less neutrons are generated and there are few residual radioactive elements as the debugging target; there is a particle migration layer 2 between the target material and the target microchannel substrate layer 3, and its material is one of vanadium, tantalum, and iron.

[0044] The above embodiments are only specific embodiments of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these obvious replacement forms all belong to the protection scope of the present invention.

Claims

1. A neutron generating target, characterized in that: The neutron generation target comprises a target material layer, a particle migration layer, a microchannel substrate layer and a cover layer which are sequentially bonded and connected to form an integrated multi-layer structure target body, on which a plurality of groups of thermocouple assemblies are arranged; the thermocouple assembly comprises a thermocouple and a sleeve, the sleeve passes through the target body from the cover layer until it is close to the target material layer, and the thermocouple is inserted into the corresponding sleeve to get as close to the target material as possible and infer the target material temperature; the thermocouple penetrates the target cover layer and the surface fins of the microchannel substrate layer to the bottom of the microchannel substrate layer; the surface of the microchannel substrate layer is processed with a plurality of The fins are arranged in rows, and tiny heat dissipation channels are formed between adjacent fins. The fins in each row are arranged equidistantly. The fins are made of copper, aluminum, nickel, iron, or an alloy of one of these materials. The bottom surface of the cover layer is fitted and connected with the microchannel base layer, and the microchannel base layer is closed at the bottom by welding or threaded fastening to form a cavity structure with the microchannel base layer. The inlet and outlet of the cooling medium are arranged at both ends of the cavity, and an expansion domain is provided between the inlet and outlet and the microchannel structure so that the flow rate of the fluid in and out of each channel is equal or close, thereby achieving uniform heat exchange.

2. A neutron generation target according to claim 1, characterized in that: The thermocouple components are evenly distributed on the target structure, penetrating the target from the cover layer until they are close to the target material layer.

3. A neutron generation target according to claim 1, characterized in that: The bottom surface of the cover plate layer is bonded to the microchannel base layer, and the cover plate layer is sealed by welding or threaded fastening to surround the microchannel base layer at the bottom and form a cavity structure with the microchannel base layer.

4. A neutron generation target according to claim 3, characterized in that: The two ends of the cavity are provided with an inlet and an outlet for the cooling medium, and an expansion area is provided between the inlet and the outlet and the microchannel structure so that the flow rate of the fluid in and out of each channel is equal or close, thereby achieving uniform heat exchange.

5. A neutron generation target according to claim 1, characterized in that: The upper surface of the microchannel substrate layer is bonded and connected to the cover plate layer, and the lower surface is bonded and connected to the particle migration layer by diffusion welding or coating.

6. A neutron generation target according to claim 1, characterized in that: The height dimensions of the particle migration layer and the target material layer are lower than the dimension of the central cooling area of ​​the microchannel substrate layer.

7. A neutron production target according to claim 1, characterized in that: The fins use graphite as the heat exchange material.

8. A neutron generation target according to claim 1, characterized in that: The working medium inlet and outlet of the microchannel substrate layer are expanded in combination with the micro heat dissipation channels, so that the flow distribution inside each micro heat dissipation channel is the same or close.

9. A neutron production target according to claim 1, characterized in that: The target material layer uses one of lithium, carbon, beryllium, aluminum and tungsten as a raw material.

10. A neutron production target according to claim 9, characterized in that: When the target layer uses aluminum as the raw material, no or less neutrons are generated and the residual radioactive elements are less as a debugging target.

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