Neutron source target material and preparation method thereof

Abstract

The invention provides a neutron source target material and a preparation method thereof, and the preparation method comprises the following steps: sequentially forming a bottom layer, a transition layer, a functional film layer and a protective film layer on a substrate to prepare a target film with a multilayer structure; carrying out degassing activation on the target film, wherein the degassing activation adopts a circulating heating mode from room temperature to 550 DEG C to carry out degassing; then, filling deuterium gas or tritium gas into the preparation chamber, and carrying out preliminary activation on the surface of the target film; then starting from room temperature, adopting a mode of heating while charging deuterium gas or tritium gas, enabling the target film to slowly adsorb the deuterium gas or tritium gas, and stopping charging until the temperature is greater than or equal to 500 DEG C; slowly cooling to room temperature, and continuously adsorbing deuterium gas or tritium gas by the target film until saturation to form a deuterium target or tritium target; and finally sealing the prepared deuterium target or tritium target. The preparation method has the advantages of being good in degassing effect, high in gas suction efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of neutron source target materials, and in particular to a neutron source target material and a preparation method thereof. Background Art

[0002] Deuterium / tritium targets for neutron sources are essential key components in nuclear science research and applications, and their performance directly affects the efficiency and stability of neutron sources. The traditional deuterium / tritium target preparation process mainly relies on the vacuum coating technology of titanium metal film on molybdenum substrate or copper substrate. This technology provides the necessary surface area for subsequent deuterium or tritium adsorption by forming a thin film layer several microns thick.

[0003] During the preparation process, a target film is first formed on a selected substrate by a vacuum coating method. Subsequently, in order to remove the impurity elements adsorbed on the surface of the target film, the target film is heated to a certain constant temperature and vacuum degassed. This step is crucial to improving the purity of the target film and the subsequent deuterium / tritium absorption capacity. However, in the traditional heating degassing process, the temperature is constant and relatively low, resulting in limited degassing effect, and more impurity elements may still remain on the surface of the target film, thereby weakening its ability to absorb deuterium / tritium. Next, the target film is filled with deuterium or tritium gas for adsorption at room temperature or a certain constant temperature. This step is the key link in forming a deuterium target or a tritium target. However, due to the choice of adsorption at room temperature or a lower constant temperature, the absorption efficiency is often low, resulting in the difficulty of achieving the ideal value of the tritium absorption density. This not only affects the performance of the target, but may also limit the yield of the neutron source. In addition, the traditional deuterium / tritium target preparation process also has problems such as weak bonding between the target film and the substrate, and the target film is easy to peel or fall off during the deuterium or tritium filling process. These problems not only affect the stability and service life of the target, but also may pose a potential threat to the safe operation of the neutron source.

[0004] Therefore, it is necessary to provide a new technical solution to solve at least one of the above technical problems. Summary of the invention

[0005] The present invention provides a neutron source target material and a preparation method thereof, which are used to solve the problem that the existing deuterium / tritium target preparation process has obvious deficiencies in degassing effect, air absorption efficiency and the like.

[0006] The present invention provides a method for preparing a neutron source target material, comprising the following steps: Step 1, forming a primer layer, a transition layer, a functional film layer and a protective film layer on a substrate in sequence, wherein the primer layer, the transition layer, the functional film layer and the protective film layer form a target film with a multi-layer structure; Step 2, degassing and activating the target film, wherein the degassing and activation is performed by cyclic heating from room temperature to 550° C.; Step 3: Fill the preparation chamber with deuterium or tritium gas to preliminarily activate the surface of the target film. Then, starting from room temperature, adopt the mode of filling deuterium or tritium gas while heating up, so that the target film slowly adsorbs deuterium or tritium gas until the temperature is greater than or equal to 500 °C, and then stop filling the gas. After that, slowly cool down to room temperature, and at the same time, the target film continues to adsorb deuterium or tritium gas until saturation, forming a deuterium target or a tritium target. Step 4: Seal the prepared deuterium target or tritium target.

[0007] According to the preparation method of the neutron source target material provided by the present invention, before the step 1, the preparation method further includes the following steps: Pretreat the substrate to be coated to remove the oil stains, impurity elements and surface oxide layer adsorbed on the surface of the substrate.

[0008] According to the preparation method of the neutron source target material provided by the present invention, after pretreating the substrate to be coated and before forming the underlayer, the preparation method further includes the following steps: First, evacuate the coating chamber, then heat the substrate to remove gas, and then bombard and clean the surface of the substrate with an argon ion source.

[0009] According to the preparation method of the neutron source target material provided by the present invention, after the step 1, the preparation method further includes the following steps: Under vacuum conditions, degas the pipeline in the production system by means of cyclic heating from room temperature to 120 °C.

[0010] According to the preparation method of the neutron source target material provided by the present invention, the time for degassing and heating the pipeline is at least 24 hours.

[0011] According to the preparation method of the neutron source target material provided by the present invention, after the step 3 and before the step 4, the preparation method further includes the following steps: Recover the residual gas in the pipeline of the production system.

[0012] According to the preparation method of the neutron source target material provided by the present invention, in the step 2, degas and activate the target film under vacuum conditions for at least 48 hours.

[0013] According to the preparation method of the neutron source target material provided by the present invention, when filling deuterium or tritium gas into the preparation chamber in the step 3, the pressure in the preparation chamber is controlled within the range of 10 Pa to 90 Pa.

[0014] The present invention also provides a neutron source target material, which is prepared by using the preparation method of the neutron source target material described in any one of the above.

[0015] According to the neutron source target material provided by the present invention, the deuterium-titanium ratio or tritium-titanium ratio of the target material is 1.95.

[0016] The above technical solution of the present invention has the following beneficial effects: For the neutron source target material and its preparation method of the present invention, the target film is degassed and activated by a cyclic heating method, eliminating the problems of poor degassing and activation effect at a certain constant temperature and poor deuterium / tritium absorption performance in the traditional method; it also adopts the method of first filling the preparation chamber with deuterium or tritium gas at room temperature to preliminarily activate the surface of the target film, release the stress between the lattices, and form active adsorption points. Then, the mode of filling deuterium or tritium gas while heating is adopted to enable the target film to slowly adsorb deuterium or tritium gas. Finally, it is slowly cooled to room temperature, and at the same time, the target film continues to adsorb deuterium or tritium gas until saturation to form a deuterium target or a tritium target, overcoming the disadvantages of low gas absorption efficiency and low deuterium / tritium absorption density at a certain constant temperature in the traditional method. The target material prepared by this method has the advantages of high deuterium / tritium absorption density and high neutron yield. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a flowchart of the preparation method of the neutron source target material provided by the embodiment of the present invention. Detailed Embodiments

[0019] To make the purpose, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0020] Refer to Figure 1 , the present invention provides a preparation method of a neutron source target material, including the following steps: Step 1, a primer layer, a transition layer, a functional film layer and a protective film layer are sequentially formed on a substrate, and the primer layer, the transition layer, the functional film layer and the protective film layer form a multi-layer target film.

[0021] Among them, in order to prepare a high-purity target film with strong bonding force and low impurity content, before step 1, the preparation method further includes the following steps: The substrate to be coated is pretreated to remove the adsorbed oil, impurity elements, and surface oxide layer on the substrate surface.

[0022] Specifically, ultrasonic cleaning can be used to remove the oil on the substrate surface, and hydrofluoric acid cleaning can be used to remove the oxide layer on the substrate surface, etc.

[0023] Furthermore, after the pretreatment of the substrate to be coated and before the formation of the bottom layer, the preparation method further includes the following steps: First, evacuate the coating chamber, then heat the substrate to remove gas, and then bombard and clean the substrate surface with an argon ion source to expose the fresh substrate surface.

[0024] After that, taking advantage of the high energy of the ion coating process, a bottom layer with a thickness of 10 - 80 nanometers is formed on the substrate surface by controlling the coating time, and there is a strong bonding force between the bottom layer and the substrate.

[0025] Exemplarily, the thickness of the bottom layer can be 10 nanometers, 30 nanometers, 60 nanometers, or 80 nanometers.

[0026] Then, a transition layer, a functional film layer, and a protective film layer are sequentially formed on the bottom layer by sputtering coating process, and the bottom layer, the transition layer, the functional film layer, and the protective film layer form a multi-layer target film.

[0027] Specifically, after the bottom layer is formed by ion coating, the substrate is transferred to the sputtering coating chamber to start sputtering coating. By controlling the sputtering coating process parameters and combining with the deposition of the auxiliary ion source, a transition layer, a functional film layer, and a protective film layer are sequentially formed on the bottom layer to prepare a target film with a multi-layer structure.

[0028] In one embodiment, the background vacuum before coating: 5E - 4 Pa, the parameters of ion source bombarding the substrate: voltage 1400 V, current 2 A, gas flow rate 40 sccm, time 20 minutes; the parameters of ion source assisted deposition: voltage 400 V, current 1.0 A, gas flow rate 40 sccm, time 60 minutes - 120 minutes; the parameters of ion coating process: bias voltage 90 V, current 80 A, duty cycle 40%, gas flow rate 40 sccm, the pressure of the process gas in the chamber 0.19 Pa, time 30 s; the parameters of sputtering coating process: transition film layer: voltage 200 V, current 4.5 A, gas flow rate 40 sccm, the pressure of the process gas in the chamber 0.2 Pa, time 300 s; functional film layer: voltage 100 V, current 6.0 A, gas flow rate 50 sccm, the pressure of the process gas in the chamber 0.3 Pa, time 60 minutes - 120 minutes; protective film layer: voltage 200 V, current 4.5 A, gas flow rate 40 sccm, the pressure of the process gas in the chamber 0.2 Pa, time 40 s.

[0029] For the preparation process of the target film of traditional deuterium / tritium targets, the same nuclide with a single structure is adopted, and the vacuum coating process is directly used for preparation. However, the present invention adopts a target film preparation process combining multi-arc ion plating and magnetron sputtering plating, which can prepare a target film with high purity, high bonding strength and a multi-layer structure of the same nuclide.

[0030] Further, after step 1, the preparation method further includes the following steps: Under vacuum conditions, the pipelines in the production system are degassed by means of cyclic heating from room temperature to 120 °C. Among them, the time for heating and degassing the pipelines is at least 24 hours.

[0031] It should be noted that the production system refers to each chamber (such as the ion plating chamber and the sputtering plating chamber, etc.) involved in the target production process and the connected pipelines.

[0032] For the traditional degassing process of deuterium / tritium target preparation, only the target film is degassed at high temperature, and the pipelines of the process production system are not degassed. To avoid the influence of a small amount of impurity elements adsorbed on the inner wall of the pipeline on the deuterium / tritium absorption of the target film, the present invention adopts a method of cyclic heating degassing in the range of room temperature to 120 °C to degas the pipelines in the production system under vacuum conditions for at least 24 hours, thoroughly eliminating the influence of impurity elements adsorbed on the inner wall of the pipeline.

[0033] Step 2: Degas and activate the target film. The degassing and activation are carried out by means of cyclic heating from room temperature to 550 °C.

[0034] Among them, for the target film prepared by the sputtering plating method, due to the brief contact with air during the transfer process, a small amount of impurity elements will be adsorbed. To eliminate the influence, the present invention adopts a method of cyclic heating activation in the range of room temperature to 550 °C for degassing and activation under vacuum conditions for at least 48 hours to obtain a target film with good gas absorption performance. By adopting this method, the problems of poor activation effect and poor deuterium / tritium absorption performance in the traditional method of heating and degassing activation at a certain constant temperature are eliminated.

[0035] Step 3: Fill the preparation chamber with deuterium or tritium gas to preliminarily activate the surface of the target film; then, starting from room temperature, adopt a mode of filling deuterium or tritium gas while heating up, so that the target film slowly adsorbs deuterium or tritium gas until the temperature is greater than or equal to 500 °C, and stop filling the gas; then slowly cool down to room temperature, and at the same time the target film continues to adsorb deuterium or tritium gas until saturation to form a deuterium target or a tritium target.

[0036] Specifically, in a low-pressure environment, a small amount of deuterium or tritium gas is first filled into the preparation chamber to preliminarily activate the surface of the target film, release the stress between the lattices, and form active adsorption sites; then starting from room temperature, the deuterium or tritium gas is filled while heating up, so that the target film slowly adsorbs deuterium or tritium gas until the temperature is greater than or equal to 500 °C, and then the gas filling is stopped; then the temperature is slowly decreased to room temperature, and at the same time the target film continues to adsorb deuterium or tritium gas until saturation, and the chamber pressure is stable for more than 10 minutes without change, completing the gas filling. In this way, the disadvantages of low gas absorption efficiency and low deuterium / tritium absorption density of the traditional method at room temperature or a certain constant temperature are overcome.

[0037] Among them, when filling deuterium or tritium gas into the preparation chamber, the pressure in the preparation chamber is controlled within the range of 10 Pa to 90 Pa, for example, the pressure is controlled at 10 Pa, 30 Pa, 60 Pa or 90 Pa.

[0038] Further, after step 3 and before step 4, the preparation method further includes the following steps: Recover the residual gas in the pipeline of the production system.

[0039] Step 4, seal the prepared deuterium target or tritium target.

[0040] Thus, the preparation of the neutron source target material based on deuterium / tritium elements is completed.

[0041] For the deuterium / tritium target prepared by the preparation method of the present invention, the binding force between the target film and the substrate is strong, the surface of the target film is clean, the carbon and oxygen contents on the surface of the target film are small, and the neutron yield is high. After being tested by an accelerator, the neutron yield reaches 1.42E+8 n / uA / s, basically reaching the highest neutron yield that can be achieved by the current domestic technology.

[0042] The present invention also provides a neutron source target material prepared by the preparation method of the neutron source target material as described above.

[0043] Among them, theoretically, after the target material absorbs deuterium / tritium, the ratio of deuterium-titanium or tritium-titanium is 2, while the deuterium-titanium or tritium-titanium ratio of the target material prepared by the present invention is 1.95, and the absorption density of deuterium / tritium is very high.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a neutron source target, characterized in that: The following steps are involved: Step 1, forming a primer layer, a transition layer, a functional film layer and a protective film layer on a substrate in sequence, wherein the primer layer, the transition layer, the functional film layer and the protective film layer form a target film with a multi-layer structure; Step 2, degassing and activating the target film, wherein the degassing and activation is performed by cyclic heating from room temperature to 550° C.; Step 3, filling the preparation chamber with deuterium or tritium gas to preliminarily activate the surface of the target film; then starting from room temperature, adopting a mode of heating while filling with deuterium or tritium gas, so that the target film slowly adsorbs deuterium or tritium gas until the temperature is greater than or equal to 500° C., and then stopping the filling; then slowly cooling to room temperature, while the target film continues to adsorb deuterium or tritium gas until saturation, to form a deuterium target or tritium target; Step 4: sealing the prepared deuterium target or tritium target.

2. The method for preparing a neutron source target according to claim 1, characterized in that: Before step 1, the preparation method further comprises the following steps: The substrate to be coated is pretreated to remove oil stains, impurity elements and surface oxide layers adsorbed on the surface of the substrate.

3. The method for preparing a neutron source target according to claim 2, characterized in that: After pre-treating the substrate to be coated and before forming the primer layer, the preparation method further comprises the following steps: The coating chamber is firstly evacuated, and then the substrate is heated and degassed, and then the surface of the substrate is cleaned by bombardment with an argon ion source.

4. The method for preparing a neutron source target according to claim 1, characterized in that: After step 1, the preparation method further comprises the following steps: Under vacuum conditions, the pipelines in the production system are degassed by circulating heating from room temperature to 120°C.

5. The method for preparing a neutron source target according to claim 4, characterized in that: The pipeline is heated and degassed for at least 24 hours.

6. The method for preparing a neutron source target material according to claim 4, characterized in that: After step 3 and before step 4, the preparation method further comprises the following steps: Residual gas in the pipeline of the production system is recovered.

7. The method for preparing a neutron source target according to claim 1, characterized in that: In the step 2, the target film is degassed and activated under vacuum conditions for at least 48 hours.

8. The method for preparing a neutron source target according to claim 1, characterized in that: In step 3, when deuterium gas or tritium gas is filled into the preparation chamber, the pressure in the preparation chamber is controlled within the range of 10Pa to 90Pa.

9. A neutron source target material, characterized in that: The neutron source target is prepared by the method for preparing the neutron source target as described in any one of claims 1 to 8.

10. The neutron source target material according to claim 9, characterized in that: The deuterium-titanium ratio or tritium-titanium ratio of the target material is 1.95.

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