Small and convenient oxygen isotope nuclear reaction target preparation process and device

Abstract

The invention relates to a small and convenient oxygen isotope nuclear reaction target manufacturing process and device, a reaction target lining and a sputtering target material are arranged in a vacuum chamber of a magnetron sputtering target manufacturing device, a sputtering electric field is provided by adopting a radio frequency power supply, and the flow of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber are controlled; the chromium oxide film layer is sputtered on the reaction target lining at a stable rate to form a film, and the oxygen isotope nuclear reaction target is prepared. The content of nitrogen in the chromium oxide film layer prepared by the process is extremely low, the abundance of oxygen isotope reaches 70%, and the applicability of the film layer in nuclear reaction cross section measurement is greatly enhanced. The method has the remarkable advantages of efficient coating, excellent film quality, simplicity and convenience in operation, environment friendliness, energy conservation and the like. The magnetron sputtering device improves the sputtering efficiency and the power efficiency through the synergistic effect of a magnetic field and an electric field, and ensures uniform deposition and strong adhesive force of the film. The device is compact in structure, flexibly adapts to various target materials and process requirements, reduces environmental pollution and conforms to the green production concept.

Description

Technical Field

[0001] The invention belongs to the preparation technology of nuclear reaction target materials, and specifically relates to a small and convenient target preparation process and device for oxygen isotope nuclear reaction targets. Background Art

[0002] Oxygen isotope targets play a central role in nuclear reaction research. By bombarding oxygen isotope targets of different masses with high-energy particle beams (such as protons, neutrons or heavy ions), scientists can precisely control and trigger a series of complex nuclear reaction processes. These reactions not only generate a variety of new nuclides, but also reveal key scientific issues such as the structural information inside the atomic nucleus, reaction dynamics, and the mechanism of nuclear force.

[0003] Oxygen isotope targets also play a vital role in nuclear structure research. Because different oxygen isotopes have different nucleon and neutron number configurations, they exhibit unique nuclear structure characteristics. Through in-depth research on these isotope targets, scientists can gain a deeper understanding of microscopic physical phenomena such as the shell structure of the nucleus, deformation effects, collective motion patterns, and interactions between nucleons. These research results not only enrich the understanding of the basic properties of the nucleus, but also provide valuable experimental data for the verification and development of nuclear structure theory.

[0004] At present, the main oxygen isotope targets used in international experiments are as follows: for example, Ta2O5 used by LUNA, niobium oxide, liquid water and tungsten oxide used by other laboratories. The preparation method of tungsten oxide is to mix gaseous oxygen isotopes (such as 17 O2 or 18 O2) undergoes redox reaction with tungsten powder to generate powdery W 17 O3 or W 18 O3, and then use physical vapor deposition to prepare the corresponding target material. The target prepared by this method has an oxygen abundance of only 30%, which will have an adverse effect on the measurement of experimental results. The abundance of other target preparation methods is mostly not high. In order to meet the measurement requirements of some deep core astrophysics laboratories with extremely low energy, extremely low cross section, extremely low background, and high purity and abundance of large-area targets, new target preparation technologies need to be studied.

[0005] There are three stable isotopes of oxygen: 16 O. 17 O and 18 O, the relative abundance of these three isotopes in nature are 99.756%, 0.039% and 0.205% respectively. 17 O and 18 O has a very low abundance in the natural environment and cannot be used directly for target making. Therefore, enriched gas is needed as the target making gas. The target made in this way can be used for 17 O and18 O nuclear reaction research, and the purity is more than 90% 17 O and 18 The prices of O gas are 20000 / L and 6000 / L respectively. In order to improve the utilization rate, reduce the cost, increase the abundance of the target and achieve the purpose of simplicity, convenience and good effect, the small and convenient oxygen isotope nuclear reaction target making technology is specially studied. Summary of the invention

[0006] The purpose of the present invention is to provide a small and convenient oxygen isotope nuclear reaction target preparation process and device to meet the experimental needs of deep earth nuclear astrophysics laboratories for oxygen isotope targets, minimize gas loss during the target preparation process, and reduce mutual interference between oxygen isotopes to ensure the reliability of experimental research results.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A small and convenient process for making a target for oxygen isotope nuclear reaction comprises: placing a reaction target liner and a sputtering target material in a vacuum chamber of a magnetron sputtering target making device, using a radio frequency power supply to provide a sputtering electric field, controlling the flow of argon and oxygen gas filled into the vacuum chamber and the pressure in the vacuum chamber, so that a chromium oxide film layer is sputtered at a stable rate on the reaction target liner to form an oxygen isotope nuclear reaction target.

[0009] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target manufacturing process, the reaction target liner is an aluminum plate, and the sputtering target material is chromium with a purity of more than 99.9%.

[0010] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target manufacturing process, the oxygen filled into the vacuum chamber has a purity of more than 90%. 17 O or 18 O enriched gas.

[0011] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target manufacturing process, the volume ratio of argon gas and oxygen gas filled into the vacuum chamber is (5-6):1.

[0012] Furthermore, as a preferred embodiment, the flow rates of argon and oxygen filled into the vacuum chamber are V Ar =11.1~11.4sccm,V O2 =1.9~2.1sccm,V Ar is the volume flow rate of argon gas, V O2 is the volume flow rate of oxygen.

[0013] Furthermore, as the best implementation scheme, the flow rates of argon and oxygen filled into the vacuum chamber are V and Ar =11.3sccm, V O2 =2.0sccm, VAr is the volume flow rate of argon gas, V O2 is the volume flow rate of oxygen.

[0014] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target manufacturing process, the sputtering power of the RF power supply is 100-120W.

[0015] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target manufacturing process, after argon and oxygen are filled into the vacuum chamber, the gas pressure in the chamber is maintained at 3-5Pa.

[0016] Furthermore, in the above-mentioned oxygen isotope nuclear reaction target preparation process, the chromium oxide film layer is 3 μg / cm 2 The film was stably formed at a rate of / min and the sputtering time was 30min.

[0017] The above-mentioned oxygen isotope nuclear reaction target preparation process specifically includes the following steps:

[0018] (1) placing the reaction target substrate and the sputtering target material into the corresponding position of the vacuum chamber of the magnetron sputtering target making device;

[0019] (2) Evacuate the vacuum chamber and introduce argon gas for two to three times for purge;

[0020] (3) Pump the vacuum chamber to a high vacuum, fill the vacuum chamber with argon gas, and turn on the sputtering power supply to remove the oxide layer on the surface of the target material;

[0021] (4) evacuating the vacuum chamber to a high vacuum again, filling the vacuum chamber with argon and oxygen at a set speed and ratio, and turning on the sputtering power supply to allow the chromium oxide film to be sputtered onto the reaction target substrate at a stable rate;

[0022] (5) After sputtering is completed, the film thickness is calculated and the completed reaction target is vacuum packaged.

[0023] A small and convenient oxygen isotope nuclear reaction target making device for realizing the above-mentioned process comprises a vacuum chamber for arranging a reaction target liner and a sputtering target material, a sputtering power supply connected to the sputtering pole of a magnetron target and a water cooling pipe for cooling the magnetic head and the target material are arranged at the upper end of the vacuum chamber, the sputtering power supply is connected to a radio frequency power supply, the vacuum chamber is connected to a vacuum pump and a molecular pump for providing a vacuum environment, an oxygen isotope gas inlet and an argon gas inlet are arranged on the wall of the vacuum chamber, the oxygen isotope gas inlet is connected to an oxygen supply pipeline, the argon gas inlet is connected to an argon supply pipeline, gas flow meters are respectively arranged on the oxygen supply pipeline and the argon supply pipeline, and a chromium oxide film layer is sputtered and formed on the reaction target liner at a stable rate by controlling the flow of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber.

[0024] The beneficial effects of the present invention are as follows: the present invention uses chromium as a target material to prepare an oxygen isotope nuclear reaction target, and precisely controls the process parameters, so that the nitrogen content in the prepared chromium oxide film layer is extremely low and almost negligible, which greatly enhances the applicability of the film layer in nuclear reaction cross-section measurement. The results of in-depth analysis of the film layer using secondary particle excitation detection technology show that the oxygen isotope abundance in the chromium oxide film layer reaches 70%, which is significantly superior to that of films made of other materials or under other conditions.

[0025] The present invention has significant advantages such as efficient film coating, excellent film quality, simple operation, environmental protection and energy saving. The magnetron sputtering device improves the sputtering efficiency and power efficiency through the synergistic effect of the magnetic field and the electric field, ensuring uniform deposition and strong adhesion of the film. It has a compact structure and can flexibly adapt to a variety of target materials and process requirements, while reducing environmental pollution and conforming to the concept of green production. These characteristics are very helpful for nuclear physics experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a small-sized magnetron sputtering target making device in an embodiment of the present invention;

[0027] Figure 2 for Figure 1 Left view of

[0028] Figure 3 A schematic diagram of the vacuum chamber structure of a small-scale magnetron sputtering target making device in an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the dot array arrangement for testing the uniform range of the film layer in an embodiment of the present invention.

[0030] In the figure, 1. Sputtering power supply 2. Water cooling pipe 3. Vacuum pump 4. Gate valve 5. Gas flow meter 6. High vacuum gauge 7. Magnetron target 8. Vacuum chamber 9. Low vacuum gauge 10. Molecular pump 11. RF power supply 12. Sputtering target 13. Target liner placement platform 14. Oxygen isotope gas inlet 15. Argon gas inlet DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Based on a comprehensive exploration of the effects of film layers formed by sputtering of various metals under different conditions, the present invention proposes a target preparation process for oxygen isotope nuclear reaction targets. Titanium was initially selected as the sputtering target in the initial stage of testing activities. However, when the successfully sputtered titanium oxide film layer was carefully analyzed through a high-precision scanning electron microscope, the researchers observed that the film layer contained a certain amount of nitrogen. In view of the potential interference of the presence of nitrogen on the subsequent precise measurement of nuclear reaction cross sections, and the low sputtering rate of titanium oxide film layers, it was decided to carry out a series of more extensive material screening work. Through systematic testing of candidate materials including various metals such as aluminum and chromium, and comprehensive consideration of their sputtering effects and film purity, chromium was finally determined as a more suitable sputtering target.

[0033] In addition, the researchers further investigated the sputtering performance of the same metal at different gas intake rates, especially when the ratio of oxygen to argon was kept constant. The study found that when the volume ratio of argon to oxygen filled into the vacuum chamber was (5-6):1, it was possible to better balance the sputtering stability and film quality, and help reduce costs. When argon and oxygen were simultaneously filled into the vacuum chamber, the volume flow rates of argon and oxygen were V and V, respectively. Ar =11.1~11.4sccm,V O2 =1.9~2.1sccm (the best ratio is V Ar =11.3sccm, V O2 =2.0sccm), ensuring the stability of the sputtering process and the compactness of the film quality. Deviating from this condition will easily lead to sputtering failure or loose film structure. The specific experimental data are as follows:

[0034] Unified splashing time: 30min

[0035] <![CDATA[V Ar / sccm]]> <![CDATA[V O2 / sccm]]> Film unit mass thickness ug / cm2 Densification effect 11.3 2.0 100 better 10.0 3.3 120 generally 8.7 4.7 180 Poor 6.7 6.7 210 Difference

[0036] For the same metal, the researchers also conducted an in-depth study on the specific effects of different power supply types on the target sputtering rate. Under the same power conditions, the RF power supply shows a significant advantage over the DC power supply, and its sputtering rate is nearly twice that of the DC power supply. The present invention uses an RF power supply as a sputtering power supply and sets the sputtering power to 100W, because when the power is less than 80W, sputtering cannot occur and target making cannot be performed; when the power is greater than 120W, the magnetic head will be damaged due to being at high temperature for a long time.

[0037] In view of the above research, the target making process of oxygen isotope nuclear reaction target provided by the present invention includes: placing a reaction target liner (aluminum plate) and a sputtering target material (chromium with a purity of more than 99.9%) in a vacuum chamber of a magnetron sputtering target making device, using a radio frequency power supply to provide a sputtering electric field, controlling the flow rate of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber, so that a chromium oxide film layer is sputtered at a stable rate on the reaction target liner to form an oxygen isotope nuclear reaction target.

[0038] After a series of rigorous tests and evaluations such as secondary particle excitation tests, the following experimental parameters were finally established: RF power was used as the sputtering power source, the sputtering power was set to 100W, and the inflation speed and ratio were precisely controlled to V Ar =11.3sccm and V O2 =2.0sccm, and the pressure in the chamber is maintained at 3.8Pa. When the pressure is higher than 5Pa, sputtering for 30min, the film thickness is 120ug / cm 2 , but the film is loose and cannot withstand strong current; when the pressure is lower than 3Pa, the sputtering time is 30min, the film thickness is 60min, the preparation is too slow, and the consumption cost is too high, so 3.8Pa was finally selected. Under this optimal condition, the film can be stable at 3ug / cm 2 The film was formed by efficient sputtering at a rate of 1.34 nm / min, ensuring the reliability and repeatability of the experimental results. The oxygen isotope abundance in the chromium oxide film reached 70%.

[0039] The small and convenient oxygen isotope nuclear reaction target making device used in the present invention is as follows Figure 1 , Figure 2 As shown. Its structure includes a vacuum chamber 8 for setting a reaction target substrate and a sputtering target material. A sputtering power supply 1 connected to the sputtering pole of the magnetron target 7 and a water cooling pipe 2 for cooling the magnetic head and the target material are provided at the upper end of the vacuum chamber. The sputtering power supply 1 is connected to the radio frequency power supply 11 to provide a sputtering electric field. The vacuum chamber 8 is connected to a vacuum pump 3 and a molecular pump 10 for providing a vacuum environment, wherein the vacuum pump 3 is a low vacuum pump that can provide a low vacuum environment, and the molecular pump is used to provide a high vacuum environment. A gate valve 4 is provided on the vacuum pumping pipeline to control the pumping rate and the vacuum degree of the vacuum chamber. The low vacuum gauge 9 has a high accuracy within a vacuum range of 3-10Pa and is used to provide a low vacuum signal. The high vacuum gauge 6 provides a high vacuum signal. The vacuum chamber is respectively connected to an oxygen supply pipeline and an argon supply pipeline, and a gas flow meter 5 is provided on the oxygen supply pipeline and the argon supply pipeline, respectively, to control the inflation speed and maintain the air pressure in the vacuum chamber.

[0040] The structure of the vacuum chamber of the target making device is as follows Figure 3As shown, the sputtering target 12 is arranged above the vacuum chamber, and the target substrate placement platform 13 is arranged below. The volume of the vacuum chamber is 7L, and the distance between the target and the target substrate is 10-25cm. An oxygen isotope gas inlet 14 and an argon gas inlet 15 are arranged on the wall of the vacuum chamber. The oxygen isotope gas inlet 14 is connected to the oxygen supply pipeline, and the argon gas inlet 15 is connected to the argon supply pipeline. Gas flow meters are respectively arranged on the oxygen supply pipeline and the argon supply pipeline. By controlling the flow of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber, the chromium oxide film layer is sputtered and formed on the reaction target substrate at a stable rate.

[0041] The researchers used Figure 4 The target pieces arranged in a dot matrix as shown in the figure tested the uniform range of the film layer. 36 7mm*7mm aluminum target liners were placed at equal intervals on a 160mm*160mm aluminum plate. After a period of preparation, a uniform sputtering range of the film layer was obtained, as shown in the figure, which is a circular area with a diameter of 90mm. Among them, in the Φ50mm area, the uniformity of the target piece is 80.98%, and in the Φ90mm area, the uniformity of the target piece is 70.67%.

[0042] The following describes the specific process and precautions of the target making process of oxygen isotope nuclear reaction target using the above-mentioned small and convenient target making device in conjunction with specific embodiments.

[0043] 1. Prepare the reaction target liner and sputtering target. The reaction target liner is made of aluminum plate. The reaction target liner is weighed and recorded. The sputtering target is made of chromium with a purity of more than 99.9%;

[0044] 2. Place the reaction target liner and sputtering target in the corresponding position of the vacuum chamber. The reaction target liner is placed on the target liner placement platform. The sputtering target is located in the magnetron target above the target liner. When placing the sputtering target, pay attention to the fact that there is no conduction between the magnetic head and the magnetic head protection cover. You can use a multimeter to check it. Open the water cooling pipe to let in cooling water to prevent the magnetic head and target from being burned out by excessive temperature during sputtering.

[0045] 3. Turn on the low vacuum pump to pump the vacuum chamber to a low vacuum (within 20Pa), and then introduce high-purity argon gas into the vacuum chamber for two to three times of gas washing;

[0046] 4. Turn on the molecular pump to pump the vacuum chamber to high vacuum. When the vacuum degree reaches 10 -4 Pa, argon gas was introduced;

[0047] 5. Set the rate of argon filling to 2.0 sccm, stabilize the pressure in the chamber at 3.5 Pa, turn on the sputtering power, set the sputtering power to 100 W, and the sputtering time to 600 s to remove the oxide layer on the surface of the chromium target;

[0048] 6. Pump the vacuum chamber to 10 -4Pa, fill the vacuum chamber with argon and oxygen isotope gas (purity above 90%) 17 O or 18 O enriched gas), set the volume flow rate of argon to 11.3sccm, the volume flow rate of oxygen isotope gas to 2.0sccm, stabilize the chamber pressure at 3.8Pa, and set the sputtering power to 100W, which will produce 3ug / cm 2 The film was sputtered on the reaction target substrate at a speed of / min, and the sputtering time was 30min;

[0049] 7. After sputtering is completed, weigh and calculate the film thickness;

[0050] 8. Vacuum-pack the completed reaction target.

[0051] Those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. Thus, if these variations and use adaptations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and use adaptations.

[0052] The above embodiments are merely illustrative of the present invention, and the present invention may also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be considered illustrative rather than restrictive in any respect. The scope of protection of the present invention should be described by the claims, and any changes equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A small and convenient process for preparing oxygen isotope nuclear reaction targets, characterized in that: The reaction target liner and the sputtering target material are placed in the vacuum chamber of the magnetron sputtering target making device, and a radio frequency power supply is used to provide a sputtering electric field. The flow rates of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber are controlled so that a chromium oxide film is sputtered at a stable rate on the reaction target liner to form an oxygen isotope nuclear reaction target.

2. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: The reaction target liner is an aluminum plate, and the sputtering target material is chromium with a purity of more than 99.9%.

3. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: The oxygen filled into the vacuum chamber is more than 90% pure 17 O or 18 O enriched gas.

4. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: The volume ratio of argon and oxygen filled into the vacuum chamber is (5-6):

1.

5. The process for preparing oxygen isotope nuclear reaction targets according to claim 4, characterized in that: The flow rates of argon and oxygen filled into the vacuum chamber are V Ar =11.1~11.4sccm,V O2 =1.9~2.1sccm,V Ar is the volume flow rate of argon gas, V O2 is the volume flow rate of oxygen.

6. The process for preparing oxygen isotope nuclear reaction targets according to claim 5, characterized in that: The flow rates of argon and oxygen filled into the vacuum chamber are V Ar =11.3sccm, V O2 =2.0sccm, V Ar is the volume flow rate of argon gas, V O2 is the volume flow rate of oxygen.

7. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: The sputtering power of the RF power supply is 100-120W.

8. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: After filling the vacuum chamber with argon and oxygen, the pressure in the chamber is maintained at 3-5Pa.

9. The process for preparing oxygen isotope nuclear reaction targets according to claim 1, characterized in that: The chromium oxide film is 3μg / cm 2 The film was stably formed at a rate of / min and the sputtering time was 30min.

10. The process for preparing oxygen isotope nuclear reaction targets according to any one of claims 1 to 9, characterized in that: The specific steps include: (1) placing the reaction target substrate and the sputtering target material into the corresponding position of the vacuum chamber of the magnetron sputtering target making device; (2) Evacuate the vacuum chamber and introduce argon gas for two to three times for purge; (3) Pump the vacuum chamber to a high vacuum, fill the vacuum chamber with argon gas, and turn on the sputtering power supply to remove the oxide layer on the surface of the target material; (4) evacuating the vacuum chamber to a high vacuum again, filling the vacuum chamber with argon and oxygen at a set speed and ratio, and turning on the sputtering power supply to allow the chromium oxide film to be sputtered onto the reaction target substrate at a stable rate; (5) After sputtering is completed, the film thickness is calculated and the completed reaction target is vacuum packaged.

11. A small and convenient oxygen isotope nuclear reaction target making device for realizing the process described in any one of claims 1 to 10, characterized in that: The invention comprises a vacuum chamber for setting a reaction target liner and a sputtering target material. A sputtering power supply connected to a sputtering pole of a magnetron target and a water cooling pipe for cooling a magnetic head and a target material are arranged at the upper end of the vacuum chamber. The sputtering power supply is connected to a radio frequency power supply. The vacuum chamber is connected to a vacuum pump and a molecular pump for providing a vacuum environment. An oxygen isotope gas inlet and an argon gas inlet are arranged on the wall of the vacuum chamber. The oxygen isotope gas inlet is connected to an oxygen supply pipeline, and the argon gas inlet is connected to an argon supply pipeline. Gas flow meters are respectively arranged on the oxygen supply pipeline and the argon supply pipeline. By controlling the flow rates of argon and oxygen filled into the vacuum chamber and the pressure in the vacuum chamber, a chromium oxide film layer is sputtered and formed on the reaction target liner at a stable rate.

Images