System for doubly calibrating deuterium gas pumping speed based on differential pressure method and standard leak method

Abstract

The invention provides a deuterium gas pumping speed dual calibration system based on a pressure difference method and a standard leak hole method. According to the technical scheme, the device comprises a deuterium gas cylinder, a vacuum gauge, a constant-volume surge tank, a flow control valve, a leak hole, a quadrupole mass spectrometer and a vacuum pump set which are sequentially connected, a first stop valve is installed between the deuterium gas cylinder and the constant-volume surge tank, and the vacuum gauge is installed on one side of the constant-volume surge tank; the flow control valve is used for monitoring the vacuum degree in the system and the pressure after the constant-volume pressure stabilizing tank is inflated, after the flow control valve is connected with the leak hole in parallel, one end of the flow control valve is connected with the constant-volume pressure stabilizing tank, and the other end of the flow control valve is connected with the vacuum pump set through the quadrupole mass spectrometer. The device is used for quantitatively measuring the enrichment degree of the deuterium particles in the neutron source target, a quantitative analysis method is provided for improving the enrichment degree of the deuterium particles in the target, the pumping speed of the deuterium gas by the system is measured by utilizing the pressure difference change of the deuterium gas in the constant-volume surge tank and a deuterium gas standard leak hole method, mutual checking is carried out, and the measurement accuracy of the enrichment degree of the deuterium particles is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of application of a compact deuterium-deuterium accelerator neutron source in neutron measurement and irradiation, and in particular to a system for doubly calibrating a deuterium gas pumping speed based on a pressure difference method and a standard leak method. Background Art

[0002] Neutron sources are important tools for conducting research on neutron physics and neutron application technology. Currently, there are three types of commonly used neutron sources: reactor neutron sources, isotope neutron sources, and accelerator neutron sources. Accelerator neutron sources are divided into high-current neutron generators, sealed neutron tubes, and compact neutron generators. Compact neutron generators have the advantages of high safety, small size, and low operating costs. They have a wide range of application values ​​in the fields of oil well logging, explosive and drug detection, and neutron photography.

[0003] The working principle of the compact neutron generator is that the accelerated deuterium ions bombard the deuterium in the deuterium target, and deuterium-deuterium nuclear fusion occurs to produce neutrons. Its characteristic is that it can achieve a small accelerator to produce a higher neutron yield at a lower incident beam energy. The deuterium target is a key component of the compact neutron generator, usually composed of a target substrate and a target film. The selection of the target film material and the enrichment of deuterium particles in the target film directly determine the neutron yield. There are two main types of deuterium targets: one is an adsorption target, which uses titanium or other metal films as carriers for adsorbing deuterium gas, that is, after the preparation of the metal film is completed, deuterium gas is naturally adsorbed under high temperature and high pressure conditions; the other is a self-forming target, in which a layer of metal titanium film is coated on the substrate of the target, and then the active deuterium ion beam in the accelerator is used to bombard it, and deuterium particles are continuously deposited in the metal film or sheet to form a deuterium self-forming target.

[0004] Therefore, quantitative measurement of deuterium particle enrichment in the target is one of the key technologies to improve the performance of accelerator neutron sources. Since the molecular weight of deuterium atoms is very small, the method usually used is to desorb deuterium particles from the target using the principle of thermal desorption, measure the deuterium partial pressure using a quadrupole mass spectrometer, and then calculate the number of deuterium particles adsorbed in the target. For this reason, it is necessary to calibrate the deuterium pumping speed of the system quantitatively.

[0005] Based on this, the present invention designs a system for dual calibration of deuterium gas pumping speed based on the pressure difference method and the standard leak method. The deuterium gas pressure difference change in the constant volume and pressure stabilizing tank and the deuterium gas standard leak are used to measure the system's deuterium gas pumping speed, and mutual calibration is performed to ensure the accuracy of the deuterium particle enrichment measurement. Summary of the invention

[0006] The present invention provides a system for doubly calibrating the deuterium gas pumping speed based on a pressure difference method and a standard leak method, which is used for quantitatively measuring the deuterium particle enrichment in a neutron source target. The deuterium gas pumping speed of the system is measured by using the two methods of the deuterium gas pressure difference change in a constant volume pressure regulating tank and the deuterium gas standard leak, and mutual calibration is performed to ensure the accuracy of the deuterium particle enrichment measurement.

[0007] The technical solution of the present invention is as follows: a system for dual calibration of deuterium gas pumping speed based on a pressure difference method and a standard leak method, comprising a deuterium gas cylinder, a constant volume pressure-stabilizing tank, a flow control valve, a leak, a quadrupole mass spectrometer and a vacuum pump group connected in sequence, a first stop valve is installed between the deuterium gas cylinder and the constant volume pressure-stabilizing tank, a vacuum gauge is installed on one side of the constant volume pressure-stabilizing tank for monitoring the vacuum degree in the system and the pressure of the constant volume pressure-stabilizing tank after inflation, the flow control valve is connected to the leak in parallel, one end is connected to the constant volume pressure-stabilizing tank, and the other end is connected to the vacuum pump group through the quadrupole mass spectrometer;

[0008] The vacuum pump group includes a molecular pump and a mechanical pump. The exhaust pipeline of the vacuum pump group is divided into two routes, one of which is connected to the constant volume and pressure stabilizing tank through a second stop valve, and the other is connected to the quadrupole mass spectrometer.

[0009] Optionally, the deuterium gas cylinder is a stainless steel cylindrical gas cylinder, which provides a high-purity deuterium gas source for the system, and the deuterium gas cylinder is connected to the constant volume and pressure stabilizing tank through a stainless steel gas pipe.

[0010] Optionally, the vacuum gauge is a full-range vacuum gauge with a measuring range of 1.0E-8–1.1E3 hPa.

[0011] Optionally, the constant volume and pressure stabilizing tank is a stainless steel cylindrical gas cylinder, which is used to store deuterium gas at different pressures, provide a standard deuterium gas back pressure for the leak, and provide a pressure change value of the constant volume and pressure stabilizing tank when calibrating the pumping speed by the differential pressure method.

[0012] Optionally, it also includes a third stop valve and a fourth stop valve, wherein the third stop valve is connected to one side of the flow control valve, and the fourth stop valve is connected to one side of the leakage hole, and the third stop valve and the fourth stop valve are connected in parallel to the constant volume and pressure stabilizing tank.

[0013] Optionally, the flow rate control range of the flow control valve is 5E-6mbar·l / s-1250mbar·l / s, which is used to control the deuterium partial pressure in the quadrupole mass spectrometer when calibrating the deuterium pumping speed by the differential pressure method.

[0014] Optionally, the leak is a channel-type leak for conveying deuterium gas, with a leak rate of 8.0E-5 mbar·L / s at a deuterium gas back pressure of 80-120 kPa, and is used to establish a stable deuterium gas partial pressure platform in a quadrupole mass spectrometer when calibrating the pumping speed using a standard leak method.

[0015] Optionally, the quadrupole mass spectrometer measures the partial pressure of gases with a molecular weight of 0-100 in a vacuum environment, and is used to monitor the partial pressure of deuterium gas during deuterium gas pumping speed calibration of the system and maintain it at a stable level.

[0016] Optionally, the pumping speed of the molecular pump is 160-250 L / s, the pumping speed of the mechanical pump is 10-30 L / s, and the vacuum pump group draws the vacuum degree in the entire system to the order of 10E-6 Pa.

[0017] In summary, the present application includes at least one of the following beneficial technical effects:

[0018] The present invention proposes a system for double calibration of deuterium gas pumping speed based on pressure difference method and standard leak method, which is used to quantitatively measure the deuterium particle enrichment in the neutron source target, and provides a quantitative analysis method for improving the deuterium particle enrichment in the target. Further, the system uses the two methods of deuterium gas pressure difference change in the constant volume pressure tank and the deuterium gas standard leak to measure the pumping speed of the system for deuterium gas, and performs mutual calibration to ensure the accuracy of the deuterium particle enrichment measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a principle block diagram of the present invention.

[0020] Figure numerals: 1-deuterium gas cylinder; 2-vacuum gauge; 3-constant volume and pressure stabilizing tank; 4-flow control valve; 5-leak hole; 6-quadrupole mass spectrometer; 7-molecular pump; 8-mechanical pump; 9-first stop valve; 10-second stop valve; 11-third stop valve; 12-fourth stop valve. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0022] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0023] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] It should be noted that the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Example

[0028] like Figure 1 As shown, the present invention proposes a system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method, which is used to quantitatively measure the deuterium particle enrichment in the neutron source target. The deuterium gas pressure difference change in the constant volume pressure regulating tank and the deuterium gas standard leak are used to measure the pumping speed of the deuterium gas by the system, and mutual verification is performed to ensure the accuracy of the measurement of the deuterium particle enrichment. The system includes a deuterium gas cylinder 1, a vacuum gauge 2, a constant volume pressure regulating tank 3, a flow control valve 4, a leak 5, a quadrupole mass spectrometer 6, and a vacuum pump group. Specifically, in the deuterium gas pumping speed calibration system, the deuterium gas cylinder 1 is connected to the constant volume pressure regulating tank 3 by a stainless steel gas pipe, and the first stop valve 9 is used to control the on-off. The vacuum gauge 2 is located at the constant volume pressure regulating tank 3 to monitor the vacuum degree in the system and the pressure of the constant volume pressure regulating tank 3 after being inflated; the flow control valve 4 is connected to the constant volume pressure regulating tank 3 in parallel with the leak hole 5, and the other end is connected to the quadrupole mass spectrometer 6; the vacuum pump group contains a molecular pump 7 and a mechanical pump 8, and the exhaust pipeline is divided into two routes, one for obtaining high vacuum in the constant volume pressure regulating tank 3 area, and the other for obtaining high vacuum at the quadrupole mass spectrometer 6. The pumping speed of the molecular pump 7 is 200L / s, and the pumping speed of the mechanical pump 8 is 20L / s. The vacuum pump group can pump the vacuum degree in the entire system to the order of 1.0E-6Pa to ensure the acquisition of an ultra-high vacuum environment when calibrating the deuterium gas pumping speed.

[0029] In this embodiment, the deuterium gas cylinder 1 is a stainless steel cylindrical gas cylinder with a volume of 8L and a deuterium gas purity of 99.9%, and is used to provide a high-purity deuterium gas source for the pumping speed system.

[0030] The vacuum gauge 2 is a full-scale vacuum gauge with a measuring range of 1.0E-8–1.0E3 hPa, and is used to monitor the vacuum degree in the system and the pressure of the constant volume pressure regulating tank 3 after inflation.

[0031] Furthermore, the constant volume and pressure stabilizing tank 3 is a 316L stainless steel cylindrical gas cylinder with a capacity of 50ml, which is used to store deuterium gas at different pressures, provide a standard deuterium gas back pressure for the leak hole 5, and provide the pressure change value of the constant volume and pressure stabilizing tank 3 when calibrating the pumping speed by the pressure difference method.

[0032] Among them, the flow control valve 4 is a valve that can adjust the amount of air intake by controlling the opening and closing degree of the valve. The flow rate control range is 5.0E-6mbar·l / s-1250mbar·l / s, and is used to control the deuterium partial pressure in the quadrupole mass spectrometer 6 when calibrating the deuterium pumping speed by the pressure difference method.

[0033] The standard leak 5 is a channel leak, which is only suitable for the passage of deuterium gas. Under a deuterium gas back pressure of 100 kPa, the leak rate is 8.0E-5 mbar·L / s. It is used to establish a stable deuterium gas partial pressure platform in the quadrupole mass spectrometer 6 when calibrating the pumping speed using the standard leak method.

[0034] The quadrupole mass spectrometer 6 can measure the partial pressure of gases with molecular weights of 0-100 in a vacuum environment. It is mainly used to monitor the partial pressure of deuterium gas during the deuterium gas pumping speed calibration of the system and maintain it at a stable level.

[0035] The specific steps of the present invention are to fully open the first stop valve 9, the second stop valve 10, the third stop valve 11, and the fourth stop valve 12 to ensure that the gas path of the whole system is unobstructed. Molecular pump 7 and mechanical pump 8 are turned on to pump the whole system to 1.0E-6Pa level to provide a high vacuum environment for subsequent experiments. After the vacuum degree reaches the requirement, the first stop valve 9, the second stop valve 10, the third stop valve 11, and the fourth stop valve 12 are closed. Subsequently, the fourth stop valve 12 upstream of the leak hole 5 is opened so that deuterium gas can enter the system downstream through the leak hole 5. Calibration needs to record the rate at which deuterium gas passes through the leak hole 5 under different deuterium gas pressure gradients. The method for ensuring that the leak hole 5 upstream maintains different deuterium gas pressure gradients is to open the deuterium gas cylinder 1 to ensure the deuterium gas supply of the gas source, slowly open the first stop valve 9 upstream of the constant volume pressure stabilizing tank 3, and observe the deuterium gas pressure in the constant volume pressure stabilizing tank 3 through the vacuum gauge 2 at the same time. When the required pressure gradient is reached, close the first stop valve 9, use the quadrupole mass spectrometer 6 to observe downstream, and when the deuterium partial pressure is stable, record the deuterium partial pressure corresponding to this gradient. When the downstream deuterium partial pressure is guaranteed to be stable, record and record the amount of deuterium gas in the constant volume surge tank 3 in a certain period of time through the vacuum gauge 2. Then continue to slowly open the first stop valve 9, repeat the above steps, and record the deuterium partial pressure corresponding to multiple deuterium pressure gradients and the pressure of deuterium gas drop per unit time of the constant volume surge tank 3. After completing the experiment of the leak 5, close the fourth stop valve 12 before the leak 5. At the same time, open the third stop valve 11 before the flow control valve 4, and open the first stop valve 9 upstream of the constant volume surge tank 3, control the gas flow rate by the valve opening size of the flow control valve 4, and when the required gas flow pressure is reached, keep the flow size of the flow control valve 4 unchanged, and also use the quadrupole mass spectrometer 6 downstream to observe and record the deuterium partial pressure. When the deuterium partial pressure is stable, record the pressure drop of the constant volume surge tank 3 within a certain period of time. Use the same method to record multiple deuterium pressure gradient data. Finally, process the data recorded by the two methods and check each other.

[0036] The above specific embodiments are only several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method, characterized in that: The invention comprises a deuterium gas cylinder (1), a vacuum gauge (2), a constant volume pressure regulating tank (3), a flow control valve (4), a leak (5), a quadrupole mass spectrometer (6) and a vacuum pump group which are connected in sequence. A first stop valve (9) is installed between the deuterium gas cylinder (1) and the constant volume pressure regulating tank (3). A vacuum gauge (2) is installed on one side of the constant volume pressure regulating tank (3) for monitoring the vacuum degree in the system and the pressure of the constant volume pressure regulating tank (3) after being inflated. After the flow control valve (4) is connected in parallel with the leak (5), one end is connected to the constant volume pressure regulating tank (3), and the other end is connected to the vacuum pump group through the quadrupole mass spectrometer (6); The vacuum pump group comprises a molecular pump (7) and a mechanical pump (8), and the exhaust pipeline of the vacuum pump group is divided into two paths, one of which is connected to the constant volume and pressure stabilizing tank (3) through a second stop valve (10), and the other is connected to the quadrupole mass spectrometer (6).

2. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The deuterium gas cylinder (1) is a stainless steel cylindrical gas cylinder, which provides a high-purity deuterium gas source for the system. The deuterium gas cylinder (1) is connected to the constant volume and pressure stabilizing tank (3) via a stainless steel gas pipe.

3. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The vacuum gauge (2) is a full-range vacuum gauge with a measuring range of 1.0E-8–1.0E3 hPa.

4. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The constant volume and pressure stabilizing tank (3) is a stainless steel cylindrical gas cylinder, which is used to store deuterium gas at different pressures, provide a standard deuterium gas back pressure for the leak hole (5), and provide a pressure change value of the constant volume and pressure stabilizing tank (3) when calibrating the pumping speed using the pressure difference method.

5. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: It also comprises a third stop valve (11) and a fourth stop valve (12), wherein the third stop valve (11) is connected to one side of the flow control valve (4), and the fourth stop valve (12) is connected to one side of the leakage hole (5), and the third stop valve (11) and the fourth stop valve (12) are connected in parallel to the constant volume pressure stabilizing tank (3).

6. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The flow rate control range of the flow control valve (4) is 5E-6 mbar·l / s-1250 mbar·l / s, and is used to control the deuterium partial pressure in the quadrupole mass spectrometer (6) when calibrating the deuterium pumping speed using the differential pressure method.

7. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The leak hole (5) is a channel-type leak hole for conveying deuterium gas, with a leak rate of 8.0E-5 mbar·L / s at a deuterium gas back pressure of 80-120 kPa, and is used to establish a stable deuterium gas partial pressure platform in a quadrupole mass spectrometer (6) when calibrating the pumping speed using the standard leak hole method.

8. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The quadrupole mass spectrometer (6) measures the partial pressure of gases with a molecular weight of 0-100 in a vacuum environment, and is used to monitor the partial pressure of deuterium gas during deuterium gas pumping speed calibration and maintain it at a stable level.

9. A system for dual calibration of deuterium gas pumping speed based on pressure difference method and standard leak method according to claim 1, characterized in that: The pumping speed of the molecular pump (7) is 160-250 L / s, the pumping speed of the mechanical pump is 10-30 L / s, and the vacuum pump group draws the vacuum degree in the entire system to the order of 10E-6 Pa.

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