High-heat-load plasma beam heat flux density calibration method for linear plasma device

Abstract

The invention belongs to the field of plasma diagnosis and measurement, and discloses a high-heat-load plasma beam heat flux density calibration method for a linear plasma device. According to the non-contact measurement method based on the radiation temperature measurement principle, an infrared camera after temperature calibration is installed in the direction perpendicular to the propagation direction of a plasma beam; pushing the calibration graphite into a plasma beam area, and enabling the incident surface of the calibration graphite to incline by 30 degrees relative to the symmetry axis of the vacuum chamber; capturing and recording the temperature data of the incident plane of the calibration graphite in real time in the plasma discharge process by using the low / high temperature measurement range of the infrared camera; fusing the collected low / high temperature data to form complete temperature change information; and introducing the plasma beam into a three-dimensional heat conduction equation, combining thermodynamic parameters of graphite, carrying out inversion calculation to obtain the heat flux density of the plasma beam, and carrying out inclination angle correction on the heat flux density to obtain the heat flux density during vertical incidence.

Description

Technical Field

[0001] The present invention belongs to the technical field of plasma diagnosis and measurement, and particularly relates to a method for calibrating the heat flux density of a high heat load plasma beam for a linear plasma device. Background Technique

[0002] Magnetic confinement fusion energy, as a key clean energy in the future, has the potential for stable energy output and is expected to solve future energy demand problems. Tokamak is the core device for current international magnetic confinement fusion research. The outermost closed magnetic surface separates the core plasma from the boundary plasma, forming a scrape-off layer (SOL) between it and the first wall. This region, as a buffer zone between the core high-temperature plasma and the wall material, bears the particles, heat, and helium ash generated by the fusion reaction and finally guides them to the divertor. Under normal discharge conditions of the International Thermonuclear Experimental Reactor (ITER), the divertor target plate needs to withstand a steady-state heat flux density of up to 10 MW / m 2 , and in the case of abnormal discharge, the transient heat load can even be as high as 20 MW / m 2 , posing severe challenges to the divertor target plate material, cooling system, and stable operation of the fusion device.

[0003] Facing the stringent requirements of ultra-high heat load (>10 MW / m 2 ) in the divertor region of future fusion reactors, plasma-facing materials (PFMs) will undergo intense and complex plasma-wall interactions (PWI), resulting in surface damage, structural degradation, and performance decline of the materials, thereby affecting the safety and stability of the fusion reactor. Therefore, it is very important to study the tolerance of wall materials and heat load effects. In experimental studies, although tokamak devices can provide a real fusion environment, their experimental processes are complex, the discharge duration is short, the plasma is unstable, and the operating costs are high. In contrast, linear plasma devices have become an ideal platform for simulating the high heat load environment in the divertor region due to their advantages such as controllable parameters, high experimental repeatability, and long-term stable discharge. When studying the tolerance of wall materials and heat load effects through linear plasma devices, it is necessary to calibrate the heat flux density of the plasma beam generated by them to ensure the matching of experimental conditions with actual working conditions, so as to obtain reliable research results.

[0004] Currently, in the existing technologies, the methods for calibrating the heat flux density mainly include contact measurement methods such as calorimetry and Golay cells. Among them, calorimetry relies on the temperature rise of the deposited heat to calculate the heat flux density. However, if the cooling system of the experimental platform has the ability of rapid heat dissipation, the heat will be quickly transferred to the cooling medium, resulting in limited accumulated heat, decreased measurement accuracy, and low spatial resolution. In addition, the principle of the Golay cell is to use a uniformly heated metal sheet as the heat transfer medium and calculate the heat flux density by measuring the temperature gradient on its surface. The prior art CN118794554A (published on October 18, 2024) discloses a preparation and use method of a platinum thin film heat flux sensor with a long effective test time, which improves the structural strength, erosion resistance, and reliability of heat flux measurement of the platinum thin film heat flux sensor. The prior art CN109406010A (published on March 1, 2019) discloses a water-cooled Golay calorimeter, which reduces the size of the measurement probe and can be used for long-term measurement. However, under the extreme heat load conditions (>10MW / m 2 ) in the divertor target plate area, such traditional contact measurement methods have certain limitations. Ultra-high heat flux density may cause serious ablation and material degradation on the surface of the measurement probe, thereby affecting the measurement accuracy and even causing the probe to fail.

[0005] Therefore, in the linear plasma experiment simulating the high heat load environment of the divertor, the use of non-contact measurement means (such as infrared thermal imaging) has become the research focus. Compared with the traditional contact measurement methods, infrared thermal imaging can achieve remote measurement in a high heat flux environment, avoiding errors caused by probe ablation or material degradation. However, at present, the research on calibrating the heat flux density of the plasma beam generated by the linear plasma device using infrared thermal imaging is still relatively lacking, and a complete experimental method and standardized process have not been formed. Therefore, exploring the calibration method of infrared imaging in the linear plasma experiment is of great significance for improving the accuracy and reliability of heat flux density measurement. Summary of the Invention

[0006] The present invention provides a method for calibrating the heat flux density of a high heat load plasma beam for a linear plasma device to solve the measurement problem in the high heat flux density environment inside the linear plasma device.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for calibrating the heat flux density of a high heat load plasma beam for a linear plasma device, wherein the linear plasma device includes a water cooling system 1, a power supply system 2, a plasma source system 3, a calibration graphite 4, a moving platform 5, a gas cylinder 7, a flowmeter 6, an infrared camera 8, a ZeSn glass 9, a host computer 10, and a vacuum chamber 11;

[0009] The water cooling system 1 cools the plasma source system 3;

[0010] The power supply system 2 provides discharge power for the plasma source system 3;

[0011] The plasma source system 3 forms a stable high-heat-load plasma beam in the vacuum chamber 11;

[0012] The calibration graphite 4 is made of high-purity polished graphite and is used to calibrate the heat flux density of the plasma beam;

[0013] The moving platform 5 is used to move the calibration graphite 4 in the vacuum chamber 11;

[0014] The flowmeter 6 is used to control the intake of neutral gas in the gas cylinder 7;

[0015] The gas cylinder 7 is used to provide a neutral gas atmosphere;

[0016] The infrared camera 8 is used to measure the temperature data of the incident surface of the calibration graphite 4 in real time;

[0017] The ZeSn glass 9 is used to improve the infrared transmittance of the window and ensure the accurate transmission of temperature data;

[0018] The upper computer 10 is used to detect the images captured by the infrared camera 8 in real time, perform data fusion, and perform inversion calculations of the heat flux density;

[0019] The vacuum chamber 11 is used to provide a discharge environment for the plasma system 3;

[0020] The method includes the following steps:

[0021] Step 1: Define the technical parameters of the infrared camera and check whether the infrared transmittance of the first window installed with the ZeSn glass 9 exceeds 95% in the wavelength range of 6-14 μm;

[0022] Step 2: Calibrate the temperature of the infrared camera using a blackbody radiation source and establish the corresponding relationship between temperature and emissivity;

[0023] Step 3: Select high-purity polished graphite as the calibration material and measure its thermodynamic parameters;

[0024] Step 4: Install the infrared camera 8 at the first window 25 cm away from the outlet of the plasma source system 3, perpendicular to the propagation direction of the plasma beam, and adjust its field of view to ensure that complete temperature data can be captured in real time;

[0025] Step 5: In the vacuum chamber 11, move the calibration graphite 4 to the first window through the moving platform 5, and keep its incident surface inclined at an angle of 30° with respect to the cavity symmetry axis to ensure that the infrared camera 8 can completely collect the real-time change of the surface temperature of the calibration graphite 4;

[0026] Step 6: Adopt the low-temperature measurement range of the infrared camera 8 to capture and record the temperature data of the incident surface of the calibration graphite 4 in real time during the plasma discharge process;

[0027] Step 7: Adopt the high-temperature measurement range of the infrared camera 8 to capture and record the temperature data of the incident surface of the calibration graphite 4 in real time during the plasma discharge process;

[0028] Step 8: Export the temperature data collected in Step 6 and Step 7, and fuse the two sets of data to form complete temperature field information;

[0029] Step 9: Import the complete temperature data into the three-dimensional heat conduction equation, combine with the thermodynamic parameters of the calibration graphite 4, analyze the temperature change of the incident surface of the calibration graphite 4, inversely calculate the heat flux density distribution of the plasma beam, and correct the heat flux density for the tilt angle to obtain the heat flux density at normal incidence.

[0030] Further, the specific content of Step 1 is that the technical parameters include the standard temperature measurement range, data acquisition frequency, working wavelength range, and spatial resolution, and check whether the infrared transmittance of the first window of the device exceeds 95% in the wavelength range of 6 - 14μm.

[0031] Further, the temperature calibration in Step 2 is specifically as follows: Use a blackbody radiation source with a known temperature as the standard reference source, measure the response temperature of the infrared camera under different temperature conditions, and combine with the standard temperature data to fit a conversion function to convert the non-linear temperature response into a linear response.

[0032] Further, the calibration material used in Step 3 is high-purity polished graphite, and the thermal conductivity k of the calibration graphite 4 is measured by the laser flash method and fitted to an exponential function:

[0033] k = 39.3532 + 62.6777×e -0.0015(T-273.15) Formula 1

[0034] where T is the temperature and e is the exponential function; the density of the calibration graphite 4 is 1880 kg / m 3 , and the specific heat capacity is 700 J / kg·K.

[0035] Further, step eight specifically involves exporting the calibrated graphite 4 incident surface temperature data collected in step six and step seven at different temperature ranges, and performing data fusion on it; for temperature data exceeding 500 °C, the measurement data in step seven is used to replace the corresponding temperature points in step six to ensure the measurement accuracy in the high-temperature region, eliminate the error caused by the measurement range limitation, and furthermore, fuse the two sets of data to form a complete temperature field information.

[0036] Further, step nine specifically involves calculating the temperature evolution process of the calibrated graphite 4 through the three-dimensional heat conduction equation, and analyzing the heat flux distribution on the surface of the calibrated graphite 4 based on this;

[0037] The three-dimensional heat conduction equation is expressed as follows:

[0038]

[0039] where k is the thermal conductivity of the calibrated graphite 4, ρ is the density of the calibrated graphite 4, c p is the specific heat capacity of the calibrated graphite 4, and T(x, y, z, t) is the temperature distribution on the incident surface of the calibrated graphite 4.

[0040] Further, it is assumed that the plasma beam incident surface is located in the z = 0 plane, and other boundaries follow the adiabatic condition:

[0041]

[0042] The heat flux density q on the graphite surface is calculated by the following formula:

[0043]

[0044] Further, since the incident surface of the calibrated graphite is tilted by 30° relative to the cavity symmetry axis, the tilt angle will elongate the unit area relative to the perpendicular incident direction, increasing the effective area of heat flux deposition. The tilt angle can be corrected to obtain the heat flux density q at normal incidence ⊥ :

[0045]

[0046] where θ = 30°.

[0047] Further, the Alternating Direction Implicit (ADI) algorithm is adopted, that is, by solving the derivatives in each direction step by step, the computational complexity of each time step is effectively reduced.

[0048] A high-heat-load plasma beam heat flux density calibration method for a linear plasma device as described above is applicable to the field of plasma diagnosis and measurement.

[0049] The beneficial effects of the present invention are as follows:

[0050] The non-contact measurement of the present invention ensures data reliability: By adopting non-contact infrared thermal imaging technology, ablation, errors, and experimental interference caused by traditional contact temperature sensors are avoided, ensuring the accuracy and reliability of experimental data. This method is particularly suitable for real-time measurement in an environment with ultra-high heat flux density (>10 MW / m 2 ), and it can reduce the interference of the experimental environment on the test results.

[0051] The comprehensive temperature range coverage of the present invention improves accuracy: Through the selection of multi-stage temperature measurement ranges, the entire temperature range from low temperature (0 - 650 °C) to high temperature (300 - 2000 °C) is covered, accurately capturing the temperature changes on the graphite surface. By using data fusion technology, the measurement data in different temperature ranges are optimized to eliminate errors caused by measurement range limitations, improving the accuracy and reliability of heat flux density calibration.

[0052] The heat flux density inversion analysis of the present invention accurately evaluates: By combining the three-dimensional heat conduction equation to analyze the temperature changes on the incident surface of the calibration graphite, the heat flux density of the plasma beam is accurately inverted. By combining the alternating direction implicit algorithm (ADI) to optimize the calculation efficiency and accuracy, the accuracy and calculation efficiency of heat flux density inversion are significantly improved, providing support for evaluating the heat load capacity of the linear plasma device.

[0053] The high experimental repeatability of the present invention: This method has strong versatility and repeatability, can be stably applied under different experimental conditions, and ensures the reliability of measurement results. Brief Description of the Drawings

[0054] Figure 1 is a schematic diagram of the heat flux density calibration experiment in the linear plasma device of the present invention.

[0055] Figure 2 is a temperature image of the incident surface of the calibration graphite taken in the low-temperature measurement range of the present invention.

[0056] Figure 3 is a temperature image of the incident surface of the calibration graphite taken in the high-temperature measurement range of the present invention.

[0057] Figure 4 is a flowchart of the method of the present invention.

[0058] Figure 5 is a schematic diagram of the model grid discretization of the present invention.

[0059] Figure 6 is a two-dimensional distribution diagram of the heat flux density of the plasma beam corresponding to Specific Embodiment 1 of the present invention.

[0060] Figure 7It is the two-dimensional distribution diagram of the heat flux density of the plasma beam corresponding to Specific Embodiment 2 of the present invention.

[0061] Figure 8 It is the two-dimensional distribution diagram of the heat flux density of the plasma beam corresponding to Specific Embodiment 3 of the present invention.

[0062] In the figure, (1) is the water cooling system, (2) is the power supply system, (3) is the plasma source system, (4) is the calibration graphite, (5) is the moving platform, (6) is the flowmeter, (7) is the gas cylinder, (8) is the infrared camera, (9) is the ZeSn glass, (10) is the upper computer, and (11) is the vacuum chamber. Specific Embodiment

[0063] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are proposed to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0064] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0065] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification of the present application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0066] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the present application specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0067] Many specific details are set forth in the following description in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0068] This embodiment provides a method for calibrating the heat flux density of a high-heat-load plasma beam for a linear plasma device. Through non-contact infrared thermal imaging technology, data fusion technology, and three-dimensional heat conduction equation analysis method, the high-precision calibration of the heat flux density of the plasma beam of the linear plasma device is accurately achieved. Through the fusion of dual-temperature measurement ranges, it ensures full coverage from low temperature to high temperature and significantly improves the measurement accuracy. At the same time, the infrared material spectral emissivity measurement technology is adopted to effectively reduce the measurement error caused by the change of surface emissivity, further improving the reliability of the heat flux density measurement. In short, this method provides a reliable experimental calibration means for the research of linear plasma devices in high-heat-load environments and solves the measurement problem in high-heat flux density environments.

[0069] This embodiment is for a linear plasma device. The experimental schematic diagram of the device is shown in Figure 1 , and the linear plasma device includes a water cooling system 1, a power supply system 2, a plasma source system 3, a moving platform 5, a flow meter 6, a gas cylinder 7, ZeSn glass 9, a vacuum chamber 11, and a calibration graphite 4, an infrared camera 8, and a host computer 10;

[0070] The water cooling system 1 cools the plasma source system 3;

[0071] The power supply system 2 provides discharge power for the plasma source system 3;

[0072] The plasma source system 3 forms a stable high-heat-load plasma beam in the vacuum chamber 11;

[0073] The calibration graphite 4 uses high-purity polished graphite and is used to calibrate the heat flux density of the plasma beam;

[0074] The moving platform 5 is used to move the calibration graphite 4 in the vacuum chamber 11;

[0075] The flow meter 6 is used to control the intake of neutral gas in the gas cylinder 7;

[0076] The gas cylinder 7 is used to provide a neutral gas atmosphere;

[0077] The infrared camera 8 is used to measure the temperature data of the incident surface of the calibration graphite 4 in real time;

[0078] The ZeSn glass 9 is used to improve the infrared transmittance of the window and ensure the accurate transmission of temperature data;

[0079] The host computer 10 is used to detect the images captured by the infrared camera 8 in real time, perform data fusion, and perform inversion calculation of the heat flux density;

[0080] The vacuum chamber 11 is used to provide a discharge environment for the plasma system 3.

[0081] Furthermore, the water cooling system 1, the power supply system 2, the flowmeter 6 and the gas cylinder 7 are connected to the plasma source system 3 to generate a steady-state high heat load plasma beam.

[0082] Furthermore, a calibration graphite 4 is placed on the moving platform 5 in the vacuum chamber 11, and the calibration graphite 4 is moved to the first window position 25 cm away from the outlet of the plasma source system 3.

[0083] Furthermore, an infrared camera 8 is installed at the first window of the vacuum chamber 11. The window is a ZeSn glass 9, and the infrared camera 8 is connected to the host computer 10.

[0084] A method for calibrating the heat flux density of a high heat load plasma beam for a linear plasma device, which adopts a non-contact measurement method based on the principle of radiation thermometry. The method includes the following steps:

[0085] Step 1: Define the technical parameters of the infrared camera, and check whether the infrared transmittance of the first window with the ZeSn glass 9 installed on the vacuum chamber 11 of the device exceeds 95% in the wavelength range of 6 - 14 μm to ensure the efficient transmission and accurate measurement of infrared signals.

[0086] In Step 1, the infrared camera 8 of the FLIR A700sc model is selected, which has high precision and high sensitivity. Its working wavelength range is 7.5 - 14.0 μm, ensuring that it can cover most of the infrared radiation generated when the calibration graphite 4 interacts with the plasma. The technical parameters include the standard temperature measurement range, data acquisition frequency, working wavelength range, and spatial resolution. The data acquisition frequency of the camera is set to 30 Hz, which can collect temperature change data in real time. To ensure the measurement accuracy, the temperature measurement range of the camera is selected as the low temperature measurement range (0 - 650 °C) and the high temperature measurement range (300 - 2000 °C), providing detailed and comprehensive temperature field information in different temperature segments, thereby realizing high-precision heat flux density calibration.

[0087] To improve the infrared transmittance of the window, in Step 1, the observation window of the first window selects an optical grade ZnSe window 9 to ensure that the infrared transmittance in the wavelength range of 6 - 14 μm exceeds 95%. This material selection can minimize the loss of infrared radiation at the window and ensure the accurate transmission of temperature data.

[0088] Step 2: Use a blackbody radiation source to calibrate the temperature of the infrared camera, establish the corresponding relationship between temperature and emissivity, reduce the measurement error, and ensure accurate temperature information.

[0089] Further, the temperature calibration in Step 2 is specifically as follows: A blackbody radiation source with a known temperature is used as the standard reference source, and its model is SK-MH650. By measuring the response temperature of the infrared camera under different temperature conditions and combining with the standard temperature data, a conversion function is fitted to convert the non-linear temperature response into a linear response.

[0090] (1) Infrared camera temperature calibration experiment: First, aim the infrared camera at the cavity of the blackbody radiation source, and set the distance between the camera lens and the radiation source cavity to 125 cm. Set the initial temperature of the blackbody radiation source to 200 °C, and gradually increase the target temperature to 600 °C. Measure the radiation energy of the blackbody radiation source every 20 °C using the infrared camera, and record the radiation temperature T1 measured by the camera. To ensure the accuracy and reliability of the data, select the average value of the entire radiation source cavity area in the FLIR Research Studio software as the measured temperature.

[0091] (2) Temperature loss experiment of optical-grade ZnSe glass: Since the transmittance of optical-grade ZnSe glass affects the measurement of radiation temperature, a temperature loss experiment needs to be carried out. The placement positions of the infrared camera and the blackbody radiation source are the same as in step (1), but a piece of optical-grade ZnSe glass is placed in front of the infrared camera lens, and the center of the glass is flush with the infrared camera lens. During the experiment, the initial temperature of the blackbody radiation source is 200 °C, the target temperature is set to 600 °C, and the infrared camera is used to measure every 20 °C to obtain the temperature loss coefficient of the blackbody radiation passing through the ZnSe glass, thereby quantifying the influence of the ZnSe glass on the radiation temperature.

[0092] When there is no ZnSe glass in front of the camera lens, the temperature correction coefficient of the infrared camera is b revise1 , at this time, the temperature T1 measured by the infrared camera and the actual temperature T actual1 The relationship is:

[0093]

[0094] When the ZnSe glass is placed, the ZnSe glass will cause partial loss of radiation energy, making the temperature measured by the infrared camera lower than the actual temperature. At this time, the temperature correction coefficient b of the camera revise2 , the temperature T2 measured by the infrared camera and the actual temperature T actual2 The relationship is:

[0095]

[0096] This process effectively optimizes the temperature measurement accuracy of the camera, thereby ensuring accurate and reliable temperature data during the experiment.

[0097] In Step 3, high-purity polished graphite is selected as the calibration material, and its thermodynamic parameters such as thermal conductivity, density, and specific heat capacity are measured;

[0098] Furthermore, in the third step, the standard calibration material is high-purity polished graphite with a size of 80×80×80 mm and a density of 1880 kg / m 3 , and the specific heat capacity is 700 J / kg·K. The thermal conductivity of the calibration graphite 4 is measured by the laser flash method and fitted to an exponential function:

[0099] k = 39.3532 + 62.6777×e -0.0015(T-273.15) Formula 1

[0100] where T is the temperature and e is the exponential function; the density and specific heat capacity of the calibration graphite 4 are approximately constant, with a density of 1880 kg / m 3 , and the specific heat capacity is 700 J / kg·K.

[0101] Step 4: Install the infrared camera 8 at the first window 25 cm away from the outlet of the plasma source system 3, perpendicular to the propagation direction of the plasma beam, and adjust its field of view to ensure that complete temperature data can be captured in real time;

[0102] Step 5: Move the calibration graphite 4 to the first window through the moving platform 5 in the vacuum chamber 11, and keep its incident surface inclined at an angle of 30° relative to the cavity symmetry axis to ensure that the infrared camera 8 can completely collect the real-time change of the surface temperature of the calibration graphite 4;

[0103] Furthermore, in the fifth step, the calibration graphite 4 is fixed on the precisely adjustable moving platform 5 and advanced to the first window in the vacuum chamber 11 so that the plasma beam can irradiate the incident surface of the calibration graphite 4.

[0104] The calibration graphite 4 is placed on a zirconia (ZrO2) ceramic plate. The thermal conductivity of this material is much lower than that of graphite, and it has excellent heat insulation performance. During the high heat load irradiation process, the zirconia ceramic plate can effectively prevent heat from conducting to the bottom, thereby ensuring the adiabatic boundary condition of the calibration graphite 4 and improving the accuracy and stability of the measurement.

[0105] Step 6: Use the low-temperature measurement range (0 - 650 °C) of the infrared camera 8 to capture and record the temperature data of the incident surface of the calibration graphite 4 in real time during the plasma discharge process;

[0106] Step 7: Use the high-temperature measurement range (300 - 2000 °C) of the infrared camera 8 to capture and record the temperature data of the incident surface of the calibration graphite 4 in real time during the plasma discharge process;

[0107] In Steps 6 and 7 during the discharging process, the infrared camera collects data in high frame rate mode to ensure accurate capture of the rapidly changing temperature distribution. During specific measurements, the infrared camera starts collecting data 10 seconds before discharging and continuously monitors until 20 seconds after discharging, for a total of 30 seconds, and records the temperature changes on the graphite surface in real time.

[0108] Due to the limited acquisition range of the infrared camera, a single measurement cannot cover the entire heating process. To ensure the comprehensiveness and accuracy of temperature measurement, a two-stage data acquisition scheme is adopted in the experiment. The first stage uses a low-temperature measurement range of 0 - 650 °C (as Figure 2 shown) to record the temperature changes of the calibrated graphite in the initial stage, and the second stage is a high-temperature measurement range of 300 - 2000 °C (as Figure 3 shown) to cover the entire temperature rise region.

[0109] Step 8: Export the temperature data collected in Steps 6 and 7, and perform two data fusions on it to form complete temperature field information;

[0110] In the data fusion process of Step 8, to ensure the continuity of measurement data and improve the accuracy in the high-temperature region, extract the temperature data above 500 °C in the second-stage measurement and superimpose it on the first-stage data to replace the corresponding temperature points. After fusion, finally generate complete temperature field evolution information to ensure the measurement accuracy in the high-temperature region, eliminate the errors caused by the measurement range limitation, and thus improve the reliability of the heat flux density inversion calculation.

[0111] Step 9: Import the complete temperature data into the three-dimensional heat conduction equation, combine with the thermodynamic parameters of the calibrated graphite 4, analyze the temperature changes on the incident surface of the calibrated graphite 4, invert and calculate the heat flux density distribution of the plasma beam, and perform heat flux density correction for the tilt angle to obtain the heat flux density at normal incidence.

[0112] Furthermore, Step 9 is specifically as follows: Analyze the temperature changes on the plasma beam incident surface through the three-dimensional heat conduction equation to invert the heat flux density of the plasma beam. The calculation process first uses the three-dimensional heat conduction equation, considers parameters such as the thermal conductivity, density, and specific heat capacity of the material, and performs discretization processing on the space to obtain the temperature distribution at each grid point. The specific calculation flow chart is as Figure 4 shown, and the three-dimensional heat conduction equation is as follows:

[0113]

[0114] Among them, k i is the thermal conductivity of the calibrated graphite 4, k is the thermal conductivity of the calibrated graphite 4, ρ is the density of the calibrated graphite 4, c pTo calibrate the specific heat capacity of Graphite 4, T(x, y, z, t) represents the temperature distribution on the incident surface of Graphite 4.

[0115] Since the three-dimensional heat conduction equation is a partial differential equation, spatial and temporal discretization is required during the calculation process. By meshing the space, the region is divided into multiple small cells, and the temperature distribution is calculated at each node, as Figure 5 shown.

[0116] During the discretization process, the finite difference method is used to perform numerical calculations in each direction in space to approximate the solution of the three-dimensional heat conduction equation. Based on the discretized temperature field, the heat flux density is calculated through the temperature gradient. For any node (m, n, o), the calculation formulas for the heat flux density in different directions are as follows:

[0117] Heat flux density in the x direction:

[0118] The heat flux density conducted from node (m - 1, n, o) to node (m, n, o) is:

[0119]

[0120] The heat flux density conducted from node (m, n, o) to node (m + 1, n, o) is:

[0121]

[0122] Heat flux density in the y direction:

[0123] The heat flux density conducted from node (m, n - 1, o) to node (m, n, o) is:

[0124]

[0125] The heat flux density conducted from node (m, n, o) to node (m, n + 1, o) is:

[0126]

[0127] Heat flux density in the z direction:

[0128] The heat flux density conducted from node (m, n, o - 1) to node (m, n, o) is:

[0129]

[0130] The heat flux density conducted from node (m, n, o) to node (m, n, o + 1) is:

[0131]

[0132] According to the principle of energy conservation, the total change in heat flux density can be obtained and calculated by the following formula:

[0133]

[0134] There is:

[0135]

[0136] Furthermore, assuming that the incident surface of the plasma beam is located in the z = 0 plane, and other boundaries follow adiabatic conditions:

[0137]

[0138] The heat flux density q on the graphite surface is calculated by the following formula:

[0139]

[0140] Furthermore, since the incident surface of the calibrated graphite is inclined by 30° relative to the cavity symmetry axis, the inclination angle will elongate the unit area relative to the perpendicular incident direction, increasing the effective area of heat flux deposition; the inclination angle can be corrected to obtain the heat flux density q at normal incidence ⊥ :

[0141]

[0142] where θ = 30°.

[0143] Furthermore, to improve the calculation efficiency of the three-dimensional heat conduction equation, the present method adopts the alternating direction implicit algorithm (ADI). This method effectively reduces the computational complexity of each time step by solving the derivatives in each direction step by step, significantly improving the calculation speed and accuracy. The ADI algorithm is applicable to complex three-dimensional heat conduction problems. While maintaining stability, it improves the calculation efficiency, enabling it to quickly and accurately obtain the heat flux density results of the plasma beam in the linear plasma device.

[0144] This embodiment provides a method and system for calibrating the heat flux density of a high-heat-load plasma beam for a linear plasma device. Through non-contact infrared thermal imaging technology, data fusion technology, and three-dimensional heat conduction equation inversion method, high-precision calibration of the heat flux density of the plasma beam in the linear plasma device is achieved.

[0145] Through the fusion of dual-temperature measurement ranges, full coverage from low temperature to high temperature is ensured, significantly improving the measurement accuracy.

[0146] At the same time, by using the infrared material spectral emissivity measurement technology, the measurement error caused by the change of surface emissivity is effectively reduced, further improving the reliability of the heat flux density measurement.

[0147] Specific embodiments formed according to the present invention are as follows: Specific Embodiment 1:

[0149] In this embodiment, a method for calibrating the heat flux density of a high-heat-load plasma beam for a linear plasma device provided by the present invention is adopted. This method is based on non-contact infrared thermal imaging temperature measurement technology and combines the three-dimensional heat conduction equation to inversely obtain the heat flux density distribution. This method has been successfully applied to the calibration of high-heat-load plasma beams in a linear plasma device.

[0150] During the experiment, the operating conditions of the linear plasma device are set as follows: the magnetic field strength is 1.0 T, the discharge current is 120 A, and the helium gas intake is 1.4 slm. Under this operating condition, using the calibration method provided by the present invention, the peak heat flux density of the plasma beam is obtained as 20.6 MW / m 2 , and a two-dimensional distribution map of the heat flux density of the plasma beam is obtained, as shown in Figure 6 . Specific Embodiment 2:

[0152] To investigate the applicability of the present invention under different magnetic field strength conditions, during the experiment, the operating conditions of the linear plasma device are set as follows: the magnetic field strength is 1.5 T, the discharge current is 120 A, and the helium gas intake is 1.4 slm. Under this operating condition, using the calibration method provided by the present invention, the peak heat flux density of the plasma beam is obtained as 29.4 MW / m 2 , and a two-dimensional distribution map of the heat flux density of the plasma beam is obtained, as shown in Figure 7 . Specific Embodiment 3:

[0154] During the experiment, the operating conditions of the linear plasma device are set as follows: the magnetic field strength is 2.0 T, the discharge current is 120 A, and the helium gas intake is 1.4 slm. Under this operating condition, using the calibration method provided by the present invention, the peak heat flux density of the plasma beam is obtained as 39.4 MW / m 2 , and a two-dimensional distribution map of the heat flux density of the plasma beam is obtained, as shown in Figure 8 .

[0155] The above three specific embodiments demonstrate the application effects of the heat flux density calibration method proposed by the present invention under different magnetic field strengths. The experimental results show that this method has good adaptability, high measurement accuracy, and a wide range of applicability, and can achieve accurate calibration of high-heat-load plasma beams.

Claims

1. A method for calibrating the heat flux density of a high heat load plasma beam for a linear plasma device, characterized in that, The linear plasma device includes a water cooling system (1), a power supply system (2), a plasma source system (3), a calibration graphite (4), a moving platform (5), a flowmeter (6), a gas cylinder (7), an infrared camera (8), a ZeSn glass (9), a host computer (10), and a vacuum chamber (11); The water cooling system (1) cools the plasma source system (3); The power supply system (2) provides discharge power for the plasma source system (3); The plasma source system (3) forms a stable high heat load plasma beam in the vacuum chamber (11); The calibration graphite (4) is made of high-purity polished graphite and is used to calibrate the heat flux density of the plasma beam; The moving platform (5) is used to move the calibration graphite (4) in the vacuum chamber (11); The flowmeter (6) is used to control the intake of neutral gas in the gas cylinder (7); The gas cylinder (7) is used to provide a neutral gas atmosphere; The infrared camera (8) is used to measure the temperature data of the incident surface of the calibration graphite (4) in real time; The ZeSn glass (9) is used to improve the infrared transmittance of the window and ensure the accurate transmission of temperature data; The host computer (10) is used to detect the images captured by the infrared camera (8) in real time, perform data fusion, and perform inverse calculation of the heat flux density; The vacuum chamber (11) is used to provide a discharge environment for the plasma system (3); The method includes the following steps: Step 1: Define the technical parameters of the infrared camera (8), and check whether the infrared transmittance of the first window installed with the ZeSn glass (9) exceeds 95% in the wavelength range of 6-14 μm; Step 2: Calibrate the temperature of the infrared camera (8) using a blackbody radiation source to establish the corresponding relationship between temperature and emissivity; Step 3: Select high-purity polished graphite as the calibration material and measure its thermodynamic parameters; Step 4: Install the infrared camera (8) at the first window 25 cm away from the outlet of the plasma source system (3), perpendicular to the propagation direction of the plasma beam, and adjust its field of view to ensure that complete temperature data can be captured in real time; Step 5: Move the calibration graphite (4) to the first window in the vacuum chamber (11) through the moving platform (5), and keep its incident surface inclined at an angle of 30° relative to the cavity symmetry axis to ensure that the infrared camera (8) can completely collect the real-time changes in the surface temperature of the calibration graphite (4); Step 6: Use the low-temperature measurement range of the infrared camera (8) to capture and record the temperature data of the incident surface of the calibration graphite (4) in real time during the plasma discharge process; Step 7: Use the high-temperature measurement range of the infrared camera (8) to capture and record the temperature data of the incident surface of the calibration graphite (4) in real time during the plasma discharge process; Step 8: Export the temperature data collected in Step 6 and Step 7, and fuse the two data to form a complete temperature field information; Step 9: Import the complete temperature data into the three-dimensional heat conduction equation, combine with the thermodynamic parameters of the calibration graphite (4), analyze the temperature change of the incident surface of the calibration graphite (4), inversely calculate the heat flux density distribution of the plasma beam, and correct the heat flux density for the tilt angle to obtain the heat flux density at normal incidence.

2. The method according to claim 1, wherein Specifically, in Step 1, the technical parameters include the standard temperature measurement range, data acquisition frequency, working wavelength range, and spatial resolution.

3. The method according to claim 1, wherein Specifically, in Step 2 for temperature calibration, a blackbody radiation source with a known temperature is used as the standard reference source. By measuring the response temperature of the infrared camera under different temperature conditions and combining with the standard temperature data, a conversion function is fitted to convert the non-linear temperature response into a linear response.

4. The method according to claim 1, wherein The calibration material used in Step 3 is high-purity polished graphite. The thermal conductivity k of the calibration graphite 4 is measured by the laser flash method and fitted as an exponential function: k = 39.3532 + 62.6777×e -0.0015(T-273.15) Formula 1 where T is the temperature and e is the exponential function; the density of the calibrated graphite (4) is 1880 kg / m 3 , and the specific heat capacity is 700 J / kg·K.

5. The method according to claim 3, wherein Specifically, in Step 8, the temperature data of the incident surface of the calibration graphite (4) collected in Steps 6 and 7 in different temperature ranges are exported and data fusion is performed on them; for the temperature data exceeding 500 °C, the measurement data in Step 7 are used to replace the corresponding temperature points in Step 6 to ensure the measurement accuracy in the high-temperature region, eliminate the error caused by the measurement range limitation, and furthermore, fuse the two sets of data to form the complete temperature field information.

6. The method according to claim 3, characterized in that, Specifically, in Step 9, the temperature evolution process of the calibration graphite (4) is calculated by the three-dimensional heat conduction equation, and based on this, the heat flux distribution on the surface of the calibration graphite (4) is analyzed. The three-dimensional heat conduction equation is expressed as follows: where k is the thermal conductivity of the calibrated graphite (4), ρ is the density of the calibrated graphite (4), c p is the specific heat capacity of the calibrated graphite (4), and T(x, y, z, t) is the temperature distribution on the incident surface of the calibrated graphite (4).

7. The method according to claim 6, wherein Assume that the plasma beam incident surface is located in the z = 0 plane, and other boundaries follow the adiabatic condition: The heat flux density q on the graphite surface is calculated by the following formula:

8. The method according to claim 7, wherein Since the incident surface of the calibration graphite is inclined by 30° with respect to the cavity symmetry axis, the inclination angle is corrected to obtain the heat flux density q at normal incidence ⊥ : where θ = 30°.

9. According to the method described in any one of claims 6-8, characterized in that, The alternating direction implicit algorithm ADI is adopted, that is, by solving the derivatives in each direction step by step, the computational complexity of each time step is effectively reduced.

10. A method for calibrating the heat flux density of a high-heat-load plasma beam for a linear plasma device as described in any one of claims 1-9 is applicable to the field of plasma diagnosis and measurement.

Images