Rotating target for generating monoenergetic neutrons

Abstract

The invention provides a rotating target for generating monoenergetic neutrons, which comprises a target chamber, a target sheet, a sealing flange and a vacuum system, the target sheet is composed of a TiD / TiT target material and a substrate, a deviation distance of 5-10mm exists between the center of the target material and the center of the substrate, the substrate is connected with a motor outside the target chamber through a fixed connecting rod, and the target chamber is driven by the motor to rotate at a speed of 3-5min / r. The target material is designed to be the eccentric target rotating slowly, so that the utilization rate of the target material can be improved, and the phenomena that the temperature of a single point is too high, a coating layer penetrates or falls off, enriched gas escapes and neutron yield fluctuation is caused due to the fact that beam bombards one position of the target material for a long time can be avoided. The energy width of neutrons generated by the rotating target is lower than 5%, the rotating target has good monochromaticity and low energy loss, the design precision requirement of the fourth-generation nuclear reactor can be met, and a possible guarantee is provided for commercialized popularization and application of the fourth-generation nuclear reactor.

Description

Technical Field

[0001] This invention belongs to the field of neutron source technology, and specifically relates to a rotating target for generating monoenergetic neutrons. Background Technology

[0002] The design of fourth-generation nuclear reactors places higher demands on the accuracy of neutron cross-section measurements, requiring a relative standard uncertainty of less than 1% for neutron-induced standard nuclear reactions. Traditional targets are bombarded in a fixed location over extended periods. When the target temperature exceeds 200°C, prolonged bombardment can easily lead to target breakdown or melting. The thin Ti substrate layer also risks shedding under prolonged beam bombardment. Furthermore, the deuterium and tritium enriched within the target will escape as the target temperature rises, significantly reducing the target's neutron yield. Even with water cooling, existing solid targets still experience a decrease in neutron monochromaticity due to the increased proportion of scattered neutrons after a certain period of use. Due to these insurmountable defects, the energy broadening and energy density of neutrons produced after prolonged bombardment will fluctuate significantly, severely degrading the accuracy of neutron cross-section measurements and failing to meet the design accuracy requirements of fourth-generation nuclear reactors. Frequent target replacements not only increase production costs but also cause frequent interruptions to the neutron source's operation. Furthermore, significant manpower and resources are required to monitor the real-time usage of the target to prevent dangerous accidents. Therefore, there is an urgent need to design a monoenergetic neutron target that can be used for extended periods, producing monoenergetic neutrons with excellent monochromatic performance while ensuring stable neutron yield. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a rotating target for generating monoenergetic neutrons. By designing the target material as a slowly rotating eccentric target, not only can the utilization rate of the target material be improved, but also the problems of excessively high single-point temperature, coating layer peeling, enriched gas escape, and neutron yield fluctuations caused by long-term beam bombardment of a single location on the target material can be avoided. Using the rotating target of this invention ensures that the neutron monochromaticity of the generated neutrons is reduced to within 5%.

[0004] This invention discloses a rotating target for generating monoenergetic neutrons, comprising a target chamber, a target plate, a target wall, a sealing flange, and a vacuum system. The target chamber is composed of a target plate, a target wall, and a sealing flange. The target plate includes a target material and a substrate, with the center of the target material offset from the center of the substrate. The substrate is connected to a motor outside the target chamber via a fixed connecting rod, and the target chamber rotates under the drive of the motor.

[0005] Furthermore, the rotating target also includes a linkage gate valve located at the connection between the rotating target and the accelerator pipeline. When the target temperature exceeds 200°C, the linkage gate valve is closed to disconnect the rotating target from the accelerator pipeline.

[0006] Furthermore, the rotating target also includes a temperature monitoring device for monitoring the temperature of the target sheet.

[0007] Furthermore, the target chamber is connected to a vacuum gauge and a vacuum system, the vacuum gauge being used to monitor the gas pressure inside the target chamber, and the vacuum system including an oil-free dry pump and a molecular pump.

[0008] Furthermore, a cooling system is connected to the outside of the substrate to reduce the temperature of the target wafer and control the temperature of the target wafer to within 200°C.

[0009] Furthermore, the rotation speed of the target chamber is 3~5 min / r.

[0010] Furthermore, the eccentric distance between the center of the target material and the center of the substrate is 5~10mm.

[0011] Furthermore, the substrate is copper, silver, gold, tantalum and / or molybdenum, and the target material is a TiD and / or TiT target.

[0012] Furthermore, the method for preparing the target sheet includes: magnetron sputtering a Ti layer on the substrate surface, and then heating the Ti layer to adsorb deuterium and / or tritium to obtain a target sheet with TiD and / or TiT target materials.

[0013] Furthermore, the deuterium and / or tritium enrichment ratio of the target material is 1.2 to 1.5.

[0014] Compared with the prior art, the technical solution adopted in this invention can achieve the following beneficial effects: (1) This invention improves the utilization rate of solid target materials by modifying the existing solid target into a rotating target and adopting an eccentric design between the target center and the substrate center. It also avoids the problem of excessively high single-point temperature of the target material, coating layer peeling, enriched gas escape, and neutron yield fluctuations caused by long-term beam bombardment of a single position on the target surface. The rotating target of this invention can be used for a long time without frequent monitoring of the target material and replacement of the target sheet, reducing consumable costs and improving the continuity of neutron source operation.

[0015] (2) By setting a linkage gate valve at the connection between the rotating target and the accelerator pipeline, the present invention can ensure that when the target temperature is too high, especially when the temperature exceeds 200°C, the linkage gate valve will close in time, disconnecting the connection between the rotating target and the accelerator pipeline immediately, preventing the accelerator pipeline from being contaminated, and further improving the overall pipeline safety.

[0016] (3) By configuring a target temperature monitoring device and a cooling system, the present invention ensures that the target temperature is always below 200°C, which not only guarantees the safety of the target material during use, but also prevents the target material from being penetrated, melted, or detached.

[0017] (4) The neutron energy width generated by the rotating target of the present invention is less than 5%, the generated neutrons have good monochromaticity and low energy loss, which can meet the design accuracy requirements of the fourth generation nuclear reactor, and provide the possibility and safety guarantee for the commercial promotion and application of the fourth generation nuclear reactor. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the structure of the rotating target of the present invention.

[0019] Figure label: Target chamber 1, target plate 2, target wall 3, sealing flange 4, target material 5, substrate 6, fixed connecting rod 7, motor 8, accelerator pipeline 9, linkage gate valve 10, temperature monitoring device 11, vacuum gauge 12, vacuum system 13, cooling system 14, beam pipeline 15, focusing magnet 16. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0021] Assembly design of rotating target This invention proposes a rotating target for generating monoenergetic neutrons, such as... Figure 1 As shown, the rotating target includes a target chamber 1, a target plate 2, a target wall 3, a sealing flange 4, and a vacuum system 13. The target chamber 1 is composed of the target plate 2, the target wall 3, and the sealing flange 4. The target plate 2 includes a target material 5 and a substrate 6, with the center of the target material 5 offset from the center of the substrate 6. The substrate 6 is connected to a motor 8 outside the target chamber 1 via a fixed connecting rod 7, and the target chamber 1 rotates under the drive of the motor 8. The rotation speed of the target chamber 1 is preferably 3~5 min / r.

[0022] The rotating target also includes a linkage gate valve 10 located at the connection between the rotating target and the accelerator pipeline 9. When the temperature of the target plate 2 exceeds 200°C, the linkage gate valve 10 closes in time, thereby disconnecting the rotating target from the accelerator pipeline 9.

[0023] The rotating target also includes a temperature monitoring device 11 for monitoring the temperature of the target piece 2. This temperature monitoring device can employ an infrared thermal imager. When the target piece temperature exceeds 120°C, it issues an early warning and reduces the target piece heat by increasing the cooling water flow rate or decreasing the beam intensity, thus preventing the target material from being penetrated, melted, or detached, ensuring the safety of the target piece during use. When the target piece temperature exceeds 200°C, the linkage gate valve is closed, thereby disconnecting the rotating target from the accelerator pipeline and preventing contamination of the accelerator pipeline.

[0024] The target chamber 1 is connected to a vacuum gauge 12 and a vacuum system 13. The vacuum gauge 12 is used to monitor the gas pressure inside the target chamber 1. The vacuum system 13 preferably includes an oil-free dry pump and a molecular pump as a backing pump. The vacuum in the target chamber is mainly achieved by the combination of the molecular pump and the dry pump. A vacuum device gas passage with an inner diameter of Φ10mm is opened on the side wall of the rotating target chamber. The lower limit of the vacuum gauge measurement is 10. - 9 The valve connecting the pump unit is CF63. A Swagelok needle valve is installed between the pump unit and the target chamber to disconnect the pump unit from the target chamber. The overall vacuum in the target chamber should reach and maintain the ultimate vacuum within 5-10 minutes. The molecular pump selected should have a pumping rate >85 L / s for N2 and an ultimate pressure <8 × 10⁻⁶. -6 Pa, compression ratio 108. Maximum inlet flow rate is 140 sccm for water cooling and 100 sccm for air cooling. At 1250 Hz, maximum inlet pressure is 5 Pa for water cooling and 2 Pa for air cooling. Inlet flange is CF63, outlet flange is CF16. A 0.5~2 L / s oil-free dry pump is selected as the backing pump, with an ultimate vacuum of 10... - 1 Pa.

[0025] A cooling system 14 is connected to the outside of the substrate 6 to reduce the temperature of the target 2 to below 200°C. The cooling system used in this invention is preferably a water-cooling system. The side of the substrate facing the outside of the target 2 is in close contact with the cooling sleeve of the water-cooling system. The sleeve is preferably made of 304 stainless steel and has an internal Φ2~5mm circulation pipe. It is connected to the external cooling water outlet and inlet for circulating water cooling.

[0026] The substrate 6 is preferably made of copper, silver, gold, tantalum, or molybdenum, the target material 5 is preferably a TiD or TiT target, and the target wall 3 is preferably made of stainless steel.

[0027] The target chamber of the rotating target is connected to the beam line 15 via a sealing flange 4. The beam line can be a corrugated pipe. The target chamber is connected to the accelerator line via the beam line.

[0028] target fabrication process S1. Substrate Pretreatment The substrate of this invention is preferably made of copper, silver, gold, tantalum, or molybdenum. The substrate thickness can be 0.5 mm, and the substrate diameter can be Φ40~50 mm. Preferably, the substrate diameter is 5~10 mm larger than the diameter of the sputtered Ti film deposited on the substrate surface, thus forming an eccentric structure between the target center and the substrate center. The substrate is polished using SiC with a preferred abrasive grain size of #800~#4000, achieving a final polishing degree of 10 or higher. After polishing, the substrate is ultrasonically cleaned with acetone for 20~30 min, followed by ultrasonic cleaning with deionized water, and finally cleaned with anhydrous ethanol. After cleaning, the substrate surface is wiped clean with a non-woven cloth. Furthermore, the oxide layer on the substrate surface should also be removed, for example, by immersing the substrate in a 1:1 mixture of aqua regia and HF for 30 s~1 min, then cleaning it with anhydrous ethanol, air-drying it, and storing it in a vacuum chamber for later use.

[0029] S2. Magnetron sputtering of Ti films This invention utilizes magnetron sputtering to uniformly deposit Ti films onto a substrate. During magnetron sputtering, process parameters such as sputtering power, chamber vacuum, and target film thickness must be controlled. The final magnetron sputtered coating performance is characterized offline outside the magnetron sputtering coating machine. The magnetron sputtering coating machine used is equipped with an Ar ion sputtering gun, two DC sputtering power supplies, two pulsed sputtering power supplies, and one RF sputtering power supply, all with power >1kW. The coating machine chamber is connected to both hydrogen and argon gas paths. The sample stage diameter Φ is 120mm, and the sample stage rotation speed is 0~20r / min and continuously adjustable. The substrate can be heated to a maximum of 600℃, and the chamber ultimate vacuum reaches 10... -5 Pa.

[0030] Place the substrate on the sample stage and evacuate the chamber to 10°C. -5 Set the stage rotation speed (e.g., <5 r / min). Use a step-by-step heating method with an interval of <50°C. Adjust the voltage and output current of the sputtering power supply to gradually complete the sputtering deposition of the Ti film. After sputtering, turn off the sputtering power supply and cool the stage. Remove the sample and characterize the smoothness, uniformity, and thickness of the coating offline. The rougher the titanium film surface, the larger the grain spacing, and the more vacancies, the weaker the deuterium / tritium storage capacity.

[0031] S3. Adsorption of deuterium and tritium Deuterium / tritium adsorption is carried out in a vacuum reactor. A target plate with a deposited Ti film is placed on the sample stage of the reactor and continuously heated in a circulating manner to remove impurities introduced during the coating process and the oxide layer formed by air oxidation. The reaction chamber is then maintained under vacuum, and deuterium or tritium gas at 10-20 kPa is introduced into the reaction chamber, immersing the target plate in the deuterium / tritium atmosphere. Low DC power, a high-temperature sample stage, a thin Ti film, and a long hydrogen loading time are used in the reaction, as these process conditions are more suitable for deuterium / tritium adsorption. The target plate is heated by a heating wire, with the target plate temperature controlled at approximately 300℃ and the power controlled at 100W-300W. The power should not be set too low; when the power is below 50W, it will cause Ti film delamination. The rotation speed of the sample stage is set to 3 r / min. The completion of the adsorption process is determined by monitoring the changes in gas pressure inside the reactor. The initial pressure is stable, and after about 5-6 hours, the pressure drops rapidly, indicating that the adsorption capacity reaches its maximum, and adsorption is completed within 12-24 hours. After adsorption is complete, the target sheet is allowed to cool down naturally. Once the reactor temperature has cooled to room temperature, the final pressure reading is recorded to determine the amount of deuterium / tritium adsorbed.

[0032] The TiD / TiT target prepared by the above process can be used as the target sheet for the rotating target of this invention, and can be reserved for future use. The target material thickness of the target sheet used in this invention is preferably 5-15 μm, the deuterium or tritium enrichment ratio is preferably 1.2-1.5, and the target diameter can be selected according to the target chamber diameter and substrate diameter. For example, if the substrate diameter is Φ40-50 mm, the target diameter can be Φ30-45 mm, and the deviation between the target center and the substrate center should be controlled within 5-10 mm. The substrate diameter should be matched with the target chamber diameter. The target wall of the rotating target of this invention is preferably made of stainless steel, with a thickness of 2-3 mm, and can withstand 10... -5 The vacuum level is Pa, and the outer dimensions of the target chamber can be designed to be Φ55×300mm. The fixing rod on the substrate of this invention can be fixedly connected to the substrate by welding, and the fixing rod realizes the overall rotation of the target chamber under the drive of a stepper motor.

[0033] Rotating target performance test After the rotating target is assembled, the airtightness of the target chamber is tested, and the monoenergetic neutrons produced by the rotating target are characterized. The airtightness of the target chamber is tested using a helium mass spectrometer leak detector. Monoenergetic neutron characterization is the final step in evaluating whether the rotating target meets the design requirements. This is mainly achieved by bombarding the target sheet with a deuterium beam or proton beam of a certain intensity (with constant current, energy, and energy broadening). The energy broadening of the produced neutrons is then measured using a neutron detection instrument at the back end, employing the TOF method or the accompanying particle method. If the energy broadening is less than 5%, the requirements are met.

[0034] Tested with a helium mass spectrometer leak detector, the airtightness of the target chamber of the rotating target of this invention can reach 10. -7 Pa·m 3 / s, meeting the target chamber leak rate requirements. The neutron energy broadening produced by the rotating target of this invention was determined using the TOF method; the neutrons produced by the rotating target of this invention can all reach neutron energy E. n With an energy broadening of >250 keV and less than 5%, the rotating target of this invention can produce monoenergetic neutrons with excellent monochromaticity. Furthermore, by measuring the neutron fluence over time using both absolute and relative measurement methods, the neutron fluence variation of the rotating target of this invention is less than 7% over 8 hours when the beam intensity is stable, indicating that the rotating target of this invention can reduce the proportion of scattered neutrons and effectively increase neutron yield. Under completely identical beam intensity and other operating conditions, the target sheet usage time of the rotating target of this invention is at least three times longer than that of existing solid targets with the same target material thickness.

[0035] All the equipment and testing instruments used in the specific embodiments of this invention can be purchased through commercial channels.

[0036] The specific embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A rotating target for generating monoenergetic neutrons, comprising a target chamber, a target plate, a target wall, a sealing flange, and a vacuum system, wherein the target chamber is composed of the target plate, the target wall, and the sealing flange, characterized in that, The target includes a target material and a substrate, with the center of the target material offset from the center of the substrate; the substrate is connected to a motor outside the target chamber via a fixed connecting rod, and the target chamber rotates under the drive of the motor.

2. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The rotating target also includes a linkage gate valve located at the connection between the rotating target and the accelerator pipeline. When the target temperature exceeds 200°C, the linkage gate valve is closed to disconnect the rotating target from the accelerator pipeline.

3. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The rotating target also includes a temperature monitoring device for monitoring the temperature of the target sheet.

4. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The target chamber is connected to a vacuum gauge and a vacuum system. The vacuum gauge is used to monitor the gas pressure inside the target chamber, and the vacuum system includes an oil-free dry pump and a molecular pump.

5. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, A cooling system is connected to the outside of the substrate to reduce the temperature of the target wafer and control the temperature of the target wafer to within 200°C.

6. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The rotation speed of the target chamber is 3~5 min / r.

7. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The eccentric distance between the center of the target material and the center of the substrate is 5~10mm.

8. The rotating target for generating monoenergetic neutrons according to claim 1, characterized in that, The substrate is copper, silver, gold, tantalum and / or molybdenum, and the target material is TiD and / or TiT target.

9. The rotating target for generating monoenergetic neutrons according to claim 8, characterized in that, The method for preparing the target sheet includes: magnetron sputtering a Ti layer on the substrate surface, and then heating the Ti layer to adsorb deuterium and / or tritium to obtain a target sheet with TiD and / or TiT target materials.

10. The rotating target for generating monoenergetic neutrons according to claim 8, characterized in that, The target material has a deuterium and / or tritium enrichment ratio of 1.2 to 1.5.

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