A method and system for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak.

Abstract

This invention relates to a method and system for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak. First, the neutral particle energy spectrum and net corrosion or deposition rate of the material in the magnetic shadow region are measured using a low-energy neutral particle analyzer and a quartz crystal microbalance. Second, based on the measurement results from the quartz crystal microbalance, the total corrosion rate of the material by neutral particles is calculated by selecting the corresponding sputtering yield and combining it with the neutral particle energy spectrum and solid angle. Then, the conversion factor for the corresponding net corrosion or deposition rate is determined. Finally, based on the theory that the corrosion and deposition results in the magnetic shadow region of a tokamak device are determined by the competition between neutral particle corrosion and impurity deposition, the total deposition rate of impurities is obtained. This invention can accurately measure the total deposition rate of impurities in the magnetic shadow region of a tokamak in situ and in real time, helping to understand the physical mechanism of impurity deposition and providing support for the safe operation of future fusion reactors.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature plasma diagnostic technology, specifically relating to a method and system for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak. Background Technology

[0002] In tokamak devices, plasma-wall interaction (PWI) is a critical issue in fusion, directly impacting the safety and stability of the device's operation. The PWI process is complex. On one hand, the incident plasma particles can damage plasma-facing materials (PFMs) (sputtering, bubbling, evaporation, etc.), affecting component lifespan and even system safety. Beyond damage, the co-deposition effect of fuel and impurity particles on the PFM surface can also cause fuel retention.

[0003] The corrosion and deposition of PFMs are not independent but occur simultaneously. Generally, the corrosion of PFMs originates from the incident particle stream. For example, during the operation of a tokamak device, PFMs are sputtered by neutral particles and charged particles incident along magnetic field lines. The sputtered PFMs enter the plasma as impurities, and most of these impurities eventually deposit back onto the PFM surface, forming an amorphous layer of the mixed material. In summary, the net corrosion or net deposition result on the PFM surface is mainly determined by the competition among charged particles, neutral particles, and impurity deposition. When the total corrosion caused by the incident particles exceeds the total deposition of impurities, it is considered net corrosion; otherwise, it is considered net deposition.

[0004] Since charged particles move along magnetic field lines and cannot directly enter the magnetic shadow region, the corrosion deposition results in the magnetic shadow region are mainly determined by the corrosion caused by neutral particle incidence and the competition between impurity redeposition. In recent years, research on PFMs deposition in the magnetic shadow region of tokamak devices has become a hot topic. This is because tritium and impurity particles easily co-deposit in the so-called magnetic shadow region where there is no direct plasma contact, greatly affecting the tritium retention rate of the entire device and seriously threatening its safe operation. Understanding the physical mechanism of impurity deposition in tokamak devices requires in-depth analysis of the correlation between the total impurity deposition rate and specific plasma operating parameters.

[0005] Around 2000, major tokamak manufacturers worldwide conducted numerous long-term irradiation experiments on samples to study PFM deposition. By installing samples in the isomagnetic shadow region within the protective limiter and combining this with ion beam analysis, the deposition rate of PFMs for an entire round of experiments could be obtained. However, long-term irradiated samples are easily affected by wall treatment experiments, and the results obtained are difficult to help understand the physical mechanisms of PFM deposition.

[0006] Building upon long-term irradiation experiments, short-cycle controlled sample irradiation experiments have been developed on major tokamak devices using material sample testing platforms. These experiments combine sample irradiation with characterization techniques such as ion beam analysis and scanning electron microscopy. Samples are placed in a fixed location using a transport device to receive plasma irradiation under specific conditions, and are then retrieved after irradiation. Compared to long-term irradiation experiments, short-cycle controlled sample irradiation offers more controllable irradiation conditions, allowing for correlation between irradiation results and plasma parameters, thus aiding in understanding the deposition mechanism of PFMs. However, short-cycle controlled sample irradiation experiments still have some limitations. First, there is still a risk of plasma breakage during discharge, which can significantly interfere with the experimental results. Second, this measurement method cannot be performed in situ or in real-time; samples inevitably come into contact with air between the irradiation experiment and the characterization tests before and after irradiation, leading to modification of the sample surface material.

[0007] To address the aforementioned issues, several research methods enabling in-situ, real-time monitoring of PFM deposition have been developed in tokamaks, such as in-situ laser-induced spectroscopy and quartz crystal microbalance diagnostic systems. In-situ laser-induced spectroscopy analyzes the spectrum generated by the interaction of laser light with PFMs in the tokamak to obtain the elemental composition and depth distribution of the deposited layer, achieving qualitative and quantitative real-time measurement of impurity deposition. Quartz crystal microbalance, on the other hand, obtains real-time net changes in material mass based on the piezoelectric effect of quartz crystals. As mentioned earlier, the corrosion and deposition of PFMs in the magnetic shadow region of a tokamak is a complex process. The two methods described above only yield a net result after subtracting the total corrosion amount of neutral particles from the total deposition amount of impurities; the original total impurity deposition rate remains unknown, making it difficult to understand the PFM deposition process. Therefore, there is an urgent need to develop a measurement method and system capable of in-situ, real-time monitoring of the total impurity deposition rate in the magnetic shadow region of a tokamak. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a method and system for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak. This method enables in-situ, real-time, and accurate measurement of the total deposition rate of impurities in the magnetic shadow region, helping to understand the physical mechanism of impurity deposition and providing support for the safe operation of future fusion reactors.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak includes the following steps:

[0011] Step S1: During the tokamak plasma experiment operation phase, the neutral particle energy spectrum of the target magnetic shadow region is measured using a low-energy neutral particle analyzer, and the net corrosion or net deposition rate of the material in the target magnetic shadow region is measured using a quartz crystal microbalance.

[0012] Step S2: Determine the calculation method for the total corrosion rate of neutral particles on the material and the conversion factor for the net corrosion or net deposition rate based on the measurement results of the quartz crystal microbalance.

[0013] Step S3: When the measurement result of the quartz crystal microbalance is net corrosion, the net corrosion rate is subtracted from the total corrosion rate of the material by neutral particles to obtain the final total impurity deposition rate; when the measurement result of the quartz crystal microbalance is net deposition, the net deposition rate is added to the total corrosion rate of the material by neutral particles to obtain the final total impurity deposition rate.

[0014] Further, step S2 includes: first, determining whether the measurement result of the quartz crystal microbalance is net corrosion or net deposition; if the measurement result is net corrosion, then calculating the total corrosion rate of the material by neutral particles using the sputtering yield of fuel particles on the coating material on the quartz crystal surface combined with the neutral particle energy spectrum and solid angle; determining the conversion factor based on the density of the coating material on the quartz crystal surface; and converting the unit of the net corrosion rate from ng cm⁻² s⁻¹ to atoms cm⁻² s⁻¹; if the measurement result is net deposition, calculating the total corrosion rate of the material by neutral particles using the sputtering yield of fuel particles on the main impurities in the tokamak device combined with the neutral particle energy spectrum and solid angle; determining the conversion factor based on the density of the main impurities in the tokamak device; and converting the unit of the net deposition rate from ng cm⁻² s⁻¹ to atoms cm⁻² s⁻¹.

[0015] Furthermore, the quartz crystal surface has a coating material, which is a plasma-facing material, and the plasma-facing material is one of carbon, aluminum, silicon, molybdenum, tungsten and silicon carbide.

[0016] Furthermore, the main impurities in the tokamak device are the main impurity elements during plasma operation in the tokamak device under study, including carbon, tungsten, lithium, boron, and silicon.

[0017] The present invention also provides a measurement system for the total deposition rate of impurities in the magnetic shadow region of a tokamak, comprising:

[0018] The neutral particle energy spectrum measurement module uses a low-energy neutral particle analyzer to measure the neutral particle energy spectrum of the target magnetic shadow region. Specifically, it uses an electron multiplier tube to detect the signal of a pulsed neutral particle stream that has traveled a fixed distance through a chopper, obtains the flight time of the neutral particles, and calculates their energy.

[0019] The impurity net corrosion deposition rate measurement module uses a quartz crystal microbalance to measure the net corrosion or net deposition rate of the material in the target magnetic shadow area. Based on the piezoelectric effect of the quartz crystal, the change in the surface material mass is obtained by the change in the resonant frequency of the quartz crystal.

[0020] The calculation module first uses a computer to identify the measurement results of the quartz crystal microbalance. Based on the measurement results of net corrosion or net deposition, it selects the corresponding parameters to calculate the total corrosion rate of neutral particles on the material, and converts the net corrosion or net deposition rate measured by the quartz crystal microbalance to finally obtain the total deposition rate of impurities.

[0021] The beneficial effects of this invention are reflected in:

[0022] This invention provides a method and system for measuring the total impurity deposition rate in the magnetic shadow region of a tokamak. Based on the understanding that the material corrosion and deposition in the magnetic shadow region is a net result of competition between material corrosion caused by neutral particles and impurity deposition, the method uses a low-energy neutral particle analyzer and a quartz crystal microbalance to measure the neutral particle energy spectrum and the net corrosion or deposition rate of the material in the target magnetic shadow region. Based on the results from the quartz crystal microbalance, the total corrosion rate of the material by neutral particles is calculated by combining the neutral particle energy spectrum, solid angle, and corresponding sputtering yield. Then, considering the net corrosion or deposition results measured by the quartz crystal microbalance, the total impurity deposition rate is finally obtained. Compared to the current situation where there are no methods and systems for measuring the total impurity deposition rate in mainstream tokamak devices both domestically and internationally, this invention can accurately measure the total impurity deposition rate in the magnetic shadow region in situ and in real time, helping to understand the physical mechanism of impurity deposition and providing support for the safe operation of future fusion reactors. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments will be briefly introduced below.

[0024] Figure 1 A flowchart of a method for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak, provided by the present invention;

[0025] Figure 2 This is a schematic diagram of a measurement system for the total deposition rate of impurities in the magnetic shadow region of a tokamak, provided by the present invention. In the diagram: 1. Gate valve; 2. Chopper; 3. Flight pipe; 4. Electron multiplier tube; 5. Electrode flange A; 6. High-voltage power supply; 7. Preamplifier; 8. Diagnostic grounding terminal; 9. Data acquisition card A; 10. Quartz crystal; 11. Electrode flange B; 12. LC oscillation circuit; 13. Data acquisition card B; 14. Computer. Detailed Implementation

[0026] The embodiments of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments described herein are merely illustrative of the technical solution of the present invention and are not intended to limit the scope of protection of the present invention.

[0027] like Figure 1 As shown, a specific embodiment of the present invention provides a method for measuring the total deposition rate of impurities in the magnetic shadow region of a tokamak, comprising:

[0028] Step S1 uses a low-energy neutral particle analyzer and a quartz crystal microbalance to measure the neutral particle energy spectrum and net corrosion or deposition rate of the material in the target magnetic shadow region, including:

[0029] The low-energy neutral particle analyzer includes accessories such as a gate valve, chopper, flight tube, electron multiplier tube, electrode flange, high-voltage power supply, preamplifier, and data acquisition card;

[0030] The vacuum chamber containing the chopper and the vacuum chamber containing the electron multiplier tube are connected by a flight tube. Continuous neutral particles are emitted from the vacuum chamber inside the tokamak, are turned into pulses by the chopper, and after entering the electron multiplier tube, they will output an anode current signal. After being amplified by the preamplifier, they are turned into a voltage signal and recorded by the data acquisition card.

[0031] By recording the moment when a single neutral particle arrives at the chopper and electron multiplier tube and combining this with the known flight distance, the energy of the single neutral particle can be obtained. Statistical analysis of data within multiple pulse cycles can yield the neutral particle energy spectrum.

[0032] The quartz crystal microbalance includes a quartz crystal, electrode flange, data transmission line, LC oscillation circuit, data acquisition card and other accessories;

[0033] When the surface material of a quartz crystal changes due to corrosion or impurity deposition, this mechanical deformation causes a change in its oscillation frequency. After the quartz crystal resonates with an LC oscillation circuit composed of an applied AC voltage, capacitor, and inductor, the resonant frequency of the quartz crystal can be obtained and recorded using a data acquisition card.

[0034] The change in the surface mass of a quartz crystal is linearly related to the change in its resonant frequency.

[0035] Δm=-C m Δf

[0036] Where Δm is the change in the surface mass of the quartz crystal, C m Δf is a constant, and Δf is the change in the resonant frequency of the quartz crystal. Therefore, the change in the surface quality of the quartz crystal can be obtained from the change in the resonant frequency. Combined with the plasma irradiation time, the net corrosion or net deposition rate can be obtained, with the unit being ng cm⁻² s⁻¹.

[0037] Step S2 determines the calculation method for the total corrosion rate of neutral particles on the material and the conversion factor for the net corrosion or net deposition rate based on the measurement results of the quartz crystal microbalance, including:

[0038] Based on the physical sputtering theory, the formula for calculating the total corrosion rate S of neutral particles on a material is as follows:

[0039] S=∫Y(E)Γ(E)dE

[0040] Y(E) is the sputtering yield related to the neutral particle energy, type, and target material type; Γ(E) is the neutral particle flux of the incident target material; Г(E) can be obtained from the neutral particle energy spectrum combined with the solid angle; and the unit of the total corrosion rate S of the neutral particles on the material is atoms cm⁻² s⁻¹.

[0041] First, the measurement results of the quartz crystal microbalance are determined. When net corrosion occurs, the total corrosion rate of the material by neutral particles is calculated by combining the sputtering yield of fuel particles on the coating material on the quartz crystal surface with the neutral particle energy spectrum and solid angle. Based on the density of the coating material on the quartz crystal surface, a conversion factor is determined, and the unit of net corrosion rate is converted from ngcm⁻² s⁻¹ to atomscm⁻² s⁻¹. When net deposition occurs, the total corrosion rate of the material by neutral particles is calculated by combining the sputtering yield of fuel particles on the main impurities in the tokamak device with the neutral particle energy spectrum and solid angle. Based on the density of the main impurities in the tokamak device, a conversion factor is determined, and the unit of net deposition rate is converted from ngcm⁻² s⁻¹ to atomscm⁻² s⁻¹.

[0042] Step S3: When the measurement result of the quartz crystal microbalance is net corrosion, the net corrosion rate can be subtracted from the total corrosion rate of the material by neutral particles to obtain the final total impurity deposition rate.

[0043] When the measurement result of the quartz crystal microbalance is the net deposition rate, the final total deposition rate of impurities can be obtained by adding the total corrosion rate of the material by neutral particles to the net deposition rate.

[0044] Example 1:

[0045] like Figure 2 As shown, the high voltage electrode, signal electrode, and ground electrode of the electron multiplier tube 4 are all connected to the high voltage power supply 6, the preamplifier 7, and the diagnostic grounding terminal 8 respectively through the electrode flange A5.

[0046] After the plasma discharge experiment begins, as Figure 2As shown, when the gate valve 1 is opened, the continuous neutral particles are turned into pulses after passing through the chopper 2. They are then injected into the electron multiplier tube 4 through the flight pipe 3 and converted into secondary electrons. After being multiplied, the secondary electrons form an anode current signal, which is input to the preamplifier 7 through the signal electrode flange A5.

[0047] like Figure 2 As shown, the output terminal of the preamplifier 7 is connected to the input terminal of the data acquisition card A9. The preamplifier 7 converts and amplifies the anode current signal into a voltage signal and outputs it to the data acquisition card A9.

[0048] By recording the times when a single neutral particle arrives at chopper 2 and electron multiplier tube 4, and combining this with the known flight distance, the energy of a single neutral particle can be obtained. By using computer 14 to statistically analyze the data within multiple pulse cycles, the energy spectrum of the neutral particle can be obtained.

[0049] The electrodes of the quartz crystal 10 are connected to the LC oscillation circuit 12 via the electrode flange B 11, and the resonant frequency signal is transmitted to the data acquisition card B 13 for storage.

[0050] During plasma irradiation, the incident neutral particles sputter the surface material of the quartz crystal 10, resulting in a decrease in the surface material mass, while the deposition of impurities leads to an increase in the surface material mass.

[0051] The change in the quartz crystal's 10-resonance frequency before and after the plasma discharge experiment was obtained by comparing the changes.

[0052] Δm=-C m Δf

[0053] The change in surface mass of quartz crystal 10 before and after the plasma discharge experiment can be obtained. Combined with the plasma discharge time, the net corrosion or net deposition rate can be obtained, with the unit being ng cm-2 s-1.

[0054] Based on the physical sputtering theory, the formula for calculating the total corrosion rate S of neutral particles on a material is as follows:

[0055] S=∫Y(E)Γ(E)dE

[0056] Y(E) is the sputtering yield related to the neutral particle energy, type, and target material type. Г(E) is the neutral particle flux of the incident target material. Г(E) can be obtained from the neutral particle energy spectrum combined with the solid angle. The unit of the total corrosion rate S of the neutral particles on the material is atoms cm-2 s-1.

[0057] When the measurement result of quartz crystal 10 is net corrosion, the total corrosion rate of neutral particles on the material is calculated by combining the sputtering yield of fuel particles on the coating material on the surface of quartz crystal 10 with the neutral particle energy spectrum and solid angle. The conversion factor is determined based on the density of the coating material on the surface of quartz crystal 10, and the unit of net corrosion rate is converted from ng cm-2 s-1 to atoms cm-2 s-1. The total deposition rate of impurities is obtained by subtracting the net corrosion rate measured by quartz crystal 10 from the total corrosion rate of neutral particles on the material.

[0058] When the measurement result of quartz crystal 10 is net deposition, the total corrosion rate of neutral particles on the material is calculated by combining the sputtering yield of fuel particles on the main impurities in the tokamak device with the neutral particle energy spectrum and solid angle. Based on the density of the main impurities in the tokamak device, the conversion factor is determined, and the unit of net deposition rate is converted from ng cm-2 s-1 to atoms cm-2 s-1. The total deposition rate of impurities is obtained by adding the total corrosion rate of neutral particles on the material to the net deposition rate measured by quartz crystal 10.

[0059] Example 2:

[0060] Based on the method for measuring the total impurity deposition rate in the specific implementation, this embodiment 2 provides a system for measuring the total impurity deposition rate in the magnetic shadow region of a tokamak, comprising:

[0061] The neutral particle energy spectrum measurement module uses a low-energy neutral particle analyzer to measure the neutral particle energy spectrum of the target magnetic shadow region. Specifically, the pulsed neutral particle flow passing through the chopper 2 and the flight pipe 3 is detected by the electron multiplier tube 4. The generated anodic current passes through the electrode flange A 5 to the preamplifier 7 and is finally collected by the data acquisition card A 9. The neutral particle energy spectrum can be obtained by analyzing and statistically analyzing the flight time of the neutral particles through the computer 14.

[0062] The impurity net corrosion deposition rate measurement module uses a quartz crystal microbalance to measure the net corrosion or net deposition rate of the material in the target magnetic shadow area. Specifically, based on the piezoelectric effect of the quartz crystal 10, the change in the resonant frequency of the quartz crystal 10 is monitored through the LC oscillation circuit 12 to obtain the change in the surface material mass. The frequency signal is saved by the data acquisition card B13.

[0063] The calculation module uses computer 14 to first identify the measurement results of the quartz crystal microbalance, select the corresponding parameters based on the measurement results of net corrosion or net deposition to calculate the total corrosion rate of neutral particles on the material, and convert the net corrosion or net deposition rate measured by the quartz crystal microbalance to finally obtain the total deposition rate of impurities.

[0064] While specific implementation methods of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples. Various changes or modifications can be made to these implementation methods without departing from the principles and implementation of the present invention. Therefore, the scope of protection of the present invention is defined by the appended claims.

Claims

1. A method of measuring the total impurity deposition rate in the magnetic shadow of a tokamak, characterized in that, The method comprises the following steps: Step S1: during a tokamak plasma experiment operation stage, measuring neutral particle energy spectrum of a target magnetic shadow area by a low-energy neutral particle analyzer, and measuring material net erosion or net deposition rate of the target magnetic shadow area by a quartz crystal microbalance; Step S2: determining a calculation method of total neutral particle erosion rate on a material and a conversion coefficient of net erosion or net deposition rate according to the measurement result of the quartz crystal microbalance; Step S3: when the measurement result of the quartz crystal microbalance is net erosion, subtracting the net erosion rate from the total neutral particle erosion rate on the material to obtain a final total impurity deposition rate; and when the measurement result of the quartz crystal microbalance is net deposition, adding the net deposition rate to the total neutral particle erosion rate on the material to obtain the final total impurity deposition rate. The step S2 comprises: firstly determining whether the measurement result of the quartz crystal microbalance is net erosion or net deposition, if the measurement result is net erosion, calculating the total neutral particle erosion rate on the material by combining sputtering yield of fuel particles on a quartz crystal surface coating material with neutral particle energy spectrum and solid angle, determining the conversion coefficient based on the density of the quartz crystal surface coating material to convert the unit of the net erosion rate from ng cm-2 s-1 to atoms cm-2 s-1; and if the measurement result is net deposition, calculating the total neutral particle erosion rate on the material by combining sputtering yield of fuel particles on a main impurity in a tokamak device with neutral particle energy spectrum and solid angle, determining the conversion coefficient based on the density of the main impurity in the tokamak device to convert the unit of the net deposition rate from ng cm-2 s-1 to atoms cm-2 s-1.

2. The method of measuring the total impurity deposition rate in the magnetic shadow region of a tokamak according to claim 1, characterized in that, The quartz crystal surface coating material is a plasma-facing material, and the plasma-facing material is one of carbon, aluminum, silicon, molybdenum, tungsten and silicon carbide.

3. A method of measuring the total impurity deposition rate in the magnetic shadow of a tokamak according to claim 2, characterized in that: The main impurity in the tokamak device is a main impurity element during plasma operation of a studied tokamak device, and the main impurity element comprises carbon, tungsten, lithium, boron and silicon.

4. The method of measuring the total impurity deposition rate in the magnetic shadow region of a tokamak according to claim 2, characterized in that: The method comprises:

5. A measuring system for implementing a method of measuring the total impurity deposition rate in the magnetic shadow of a tokamak according to one of claims 1 to 4, characterized in that, a neutral particle energy spectrum measurement module for measuring neutral particle energy spectrum of a target magnetic shadow area by a low-energy neutral particle analyzer, specifically for obtaining flight time of neutral particles and calculating energy of the neutral particles by detecting signals of pulsed neutral particle flow that has flown a fixed distance through a chopper by an electron multiplier; an impurity net erosion deposition rate measurement module for measuring material net erosion or net deposition rate of the target magnetic shadow area by a quartz crystal microbalance, and obtaining a change amount of surface material mass of the quartz crystal by a change of resonance frequency of the quartz crystal based on a piezoelectric effect of the quartz crystal; a calculation module for firstly identifying a measurement result of the quartz crystal microbalance by a computer, selecting a corresponding parameter to calculate total neutral particle erosion rate on a material based on the measurement result of net erosion or net deposition, and converting the net erosion or net deposition rate measured by the quartz crystal microbalance to finally obtain a total impurity deposition rate. ​

Images