Pub Date : 2023-11-28DOI: 10.1088/2058-6272/ad1043
Junwei Xie, Yahong Xie, Jianglong Wei, L. Liang, Xu-Feng Peng, Yuwen Yang, Y. Gu, Chundong Hu, Yuanlai Xie
A magnetic field produced by a current flowing through the Plasma Grid (PG) is one of the solutions to reduce collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However the magnetic field diffused into the driver has some influences on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver a circular ring (absorber), of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around and improve plasma outflowing. With the application of absorber, the electron density is increased by about 35%, and the extraction current measured from extraction grid is increased from 1.02 A to 1.29 A. The results of extraction experiment with cesium injection show that both Extraction Grid (EG) current and H− current are increased when the absorber introduced.
{"title":"Experimental results of a magnetic field modification to the radio frequency driver of a negative ion source","authors":"Junwei Xie, Yahong Xie, Jianglong Wei, L. Liang, Xu-Feng Peng, Yuwen Yang, Y. Gu, Chundong Hu, Yuanlai Xie","doi":"10.1088/2058-6272/ad1043","DOIUrl":"https://doi.org/10.1088/2058-6272/ad1043","url":null,"abstract":"A magnetic field produced by a current flowing through the Plasma Grid (PG) is one of the solutions to reduce collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However the magnetic field diffused into the driver has some influences on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver a circular ring (absorber), of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around and improve plasma outflowing. With the application of absorber, the electron density is increased by about 35%, and the extraction current measured from extraction grid is increased from 1.02 A to 1.29 A. The results of extraction experiment with cesium injection show that both Extraction Grid (EG) current and H− current are increased when the absorber introduced.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139227616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-22DOI: 10.1088/2058-6272/ad0f0a
Kaixuan Ye, Zhen Zhou, Tao Zhang, Jiuyang Ma, Yumin Wang, Gongshun Li, K. Geng, Ming-Shan Wu, Fei Wen, Jia Huang, Yang Zhang, Lin Ming Shao, Shuqi Yang, Fubin Zhong, S. Gao, Lin Yu, Ziqiang Zhou, Haoming Xiang, Xiang Han, Shoubiao Zhang, Guoqiang Li, Xiang Gao
Microwave reflectometry is a powerful diagnostic that can measure the density profile and localized turbulence with high spatial and temporal resolution and will be used in ITER, so the understanding of the influence of plasma perturbations on the reflect signal is important. The characteristics of the reflect signal from profile reflectometry, the time-of-fight (TOF) signal to the MHD instabilities are investigated in EAST. Using a 1D full-wave simulation code by the FDTD method, it is well validated that the local density flattening could induce the discontinuity of the simulated TOF signal and an obvious change of reflect amplitude. Experimental TOF signals associated with different types of MHD instabilities (sawtooth, sawtooth precursors and tearing mode) are studied in detail and show agreement with the simulation. Two new improved algorithms for detecting and localizing the radial positions of the low-order rational surface, the Cross-correlation and Gradient Threshold (CGT) method and the 2D Convolutional Neural Network approach (CNN) are presented for the first time. It is concluded that the TOF signal analysis from profile reflectometry can provide a straightforward and localized measurement of the plasma perturbation from the edge to the core simultaneously and may be a complement or correction to the q-profile control, which will be beneficial for the advanced tokamak operation.
{"title":"Experimental study of core MHD behavior and novel algorithm of rational surface detection based on profile reflectometry in EAST","authors":"Kaixuan Ye, Zhen Zhou, Tao Zhang, Jiuyang Ma, Yumin Wang, Gongshun Li, K. Geng, Ming-Shan Wu, Fei Wen, Jia Huang, Yang Zhang, Lin Ming Shao, Shuqi Yang, Fubin Zhong, S. Gao, Lin Yu, Ziqiang Zhou, Haoming Xiang, Xiang Han, Shoubiao Zhang, Guoqiang Li, Xiang Gao","doi":"10.1088/2058-6272/ad0f0a","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0f0a","url":null,"abstract":"Microwave reflectometry is a powerful diagnostic that can measure the density profile and localized turbulence with high spatial and temporal resolution and will be used in ITER, so the understanding of the influence of plasma perturbations on the reflect signal is important. The characteristics of the reflect signal from profile reflectometry, the time-of-fight (TOF) signal to the MHD instabilities are investigated in EAST. Using a 1D full-wave simulation code by the FDTD method, it is well validated that the local density flattening could induce the discontinuity of the simulated TOF signal and an obvious change of reflect amplitude. Experimental TOF signals associated with different types of MHD instabilities (sawtooth, sawtooth precursors and tearing mode) are studied in detail and show agreement with the simulation. Two new improved algorithms for detecting and localizing the radial positions of the low-order rational surface, the Cross-correlation and Gradient Threshold (CGT) method and the 2D Convolutional Neural Network approach (CNN) are presented for the first time. It is concluded that the TOF signal analysis from profile reflectometry can provide a straightforward and localized measurement of the plasma perturbation from the edge to the core simultaneously and may be a complement or correction to the q-profile control, which will be beneficial for the advanced tokamak operation.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139250250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-22DOI: 10.1088/2058-6272/ad0f09
Kanchi Sunil, Rohit Shukla, Archana Sharma
Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma. The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are (1.6±0.5) × 1019 m-3 and (2.8±0.6) × 1019 m-3 for hydrogen and carbon plasma respectively and the peak temperature is (3.02±0.5) eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be (4.54±0.25) cm/μs and (1.81±0.18) cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.
{"title":"Study of plasma parameters of coaxial plasma source using triple Langmuir probe and Faraday cup diagnostics","authors":"Kanchi Sunil, Rohit Shukla, Archana Sharma","doi":"10.1088/2058-6272/ad0f09","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0f09","url":null,"abstract":"Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma. The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are (1.6±0.5) × 1019 m-3 and (2.8±0.6) × 1019 m-3 for hydrogen and carbon plasma respectively and the peak temperature is (3.02±0.5) eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be (4.54±0.25) cm/μs and (1.81±0.18) cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139247528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-20DOI: 10.1088/2058-6272/ad0e0b
Hao Xu, Shaobo Gong, Yi Yu, Min Xu, T. Lan, Zhibin Wang, Zhongbing Shi, Lin Nie, Guanyi Zhao, Hao Liu, Yixuan Zhou, Zihao Yuan, Chenyu Xiao, Jian Chen
The optical design of near-infrared phase contrast imaging (NI-PCI) diagnosis on HL-2A is introduced in this paper. This scheme benefits from the great progress of near-infrared laser technology and is broadening of traditional phase contrast technology. This diagnostic canwork as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations. Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed. The 1550 nm laser is chosen as the probe beam and high-precision optical components are designed to fit the laser beam, in which a phase plate with a 194-nm-deep silver groove is the key. Compared with the conventional 10.6 μm laser-based PCI system on HL-2A, NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm−1 to 32.6 cm−1.
{"title":"Optical design of a novel near-infrared phase contrast imaging (NI-PCI) diagnostic on the HL-2A tokamak","authors":"Hao Xu, Shaobo Gong, Yi Yu, Min Xu, T. Lan, Zhibin Wang, Zhongbing Shi, Lin Nie, Guanyi Zhao, Hao Liu, Yixuan Zhou, Zihao Yuan, Chenyu Xiao, Jian Chen","doi":"10.1088/2058-6272/ad0e0b","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0e0b","url":null,"abstract":"The optical design of near-infrared phase contrast imaging (NI-PCI) diagnosis on HL-2A is introduced in this paper. This scheme benefits from the great progress of near-infrared laser technology and is broadening of traditional phase contrast technology. This diagnostic canwork as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations. Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed. The 1550 nm laser is chosen as the probe beam and high-precision optical components are designed to fit the laser beam, in which a phase plate with a 194-nm-deep silver groove is the key. Compared with the conventional 10.6 μm laser-based PCI system on HL-2A, NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm−1 to 32.6 cm−1.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139259551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-17DOI: 10.1088/2058-6272/ad0deb
Zhiyuan Xu, Cheng Zhang, Yunjian Wu, B. Huang, Dengke Xi, Xiaoxing Zhang, T. Shao
The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma was employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline (TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species’ concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions (working gas was pure oxygen, liquid flow rate was 100mL/min, gas flow rate was 1L/min, voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/kW·h. The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after single flow under pure oxygen conditions, affording the fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.
{"title":"Single flow treatment degradation of antibiotics in water using falling-film dielectric barrier discharge","authors":"Zhiyuan Xu, Cheng Zhang, Yunjian Wu, B. Huang, Dengke Xi, Xiaoxing Zhang, T. Shao","doi":"10.1088/2058-6272/ad0deb","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0deb","url":null,"abstract":"The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma was employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline (TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species’ concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions (working gas was pure oxygen, liquid flow rate was 100mL/min, gas flow rate was 1L/min, voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/kW·h. The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after single flow under pure oxygen conditions, affording the fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139265946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-17DOI: 10.1088/2058-6272/ad0dec
Yuan Yao, Yao Yang, Ang Ti, Yang Song, Jiamin Zhang, Yan Wang, Yao Zhang, Haiqing Liu, Y. Jie
The electron density is usually diagnosed by the laser-aided interferometers. The phase difference signal obtained after phase demodulation is wrapped, which is also called fringe jump. A method has been developed to unwrap the phase difference signal in real-time by using FPGA, specifically designed to handle fringe jumps in the Hydrogen Cyanide (HCN) laser interferometer on the EAST superconducting tokamak. The method is designed for phase demodulator using the Fast Fourier Transform (FFT) method at the front end. The method is better adapted for hardware implementation compared to complex mathematical analysis algorithms, like Field Programmable Gate Array (FPGA). The method has been applied to process the phase measurement results of the HCN laser interferometer on EAST in real-time. Electron density results show a good confidence on the fringe jump unwrapping method. Further possible application on other laser interferometers, like the POlarimeter-INTerferometer (POINT) system on EAST is also discussed.
电子密度通常由激光辅助干涉仪来诊断。相位解调后得到的相位差信号会被包裹，这也被称为条纹跳跃。我们已经开发出一种方法，利用 FPGA 实时解除相位差信号的包裹，这种方法是专门为处理 EAST 超导托卡马克上的氰化氢（HCN）激光干涉仪中的条纹跳跃而设计的。该方法设计用于在前端使用快速傅立叶变换（FFT）方法的相位解调器。与现场可编程门阵列（FPGA）等复杂的数学分析算法相比，该方法更适合硬件实施。该方法已用于实时处理 EAST 上 HCN 激光干涉仪的相位测量结果。电子密度结果显示了对条纹跃迁解包方法的良好信心。此外，还讨论了在其他激光干涉仪上的进一步应用，如 EAST 上的激光干涉仪（POINT）系统。
{"title":"A fringe jump counting method for the phase measurement in the HCN laser interferometer on EAST and its FPGA-based implementation","authors":"Yuan Yao, Yao Yang, Ang Ti, Yang Song, Jiamin Zhang, Yan Wang, Yao Zhang, Haiqing Liu, Y. Jie","doi":"10.1088/2058-6272/ad0dec","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0dec","url":null,"abstract":"The electron density is usually diagnosed by the laser-aided interferometers. The phase difference signal obtained after phase demodulation is wrapped, which is also called fringe jump. A method has been developed to unwrap the phase difference signal in real-time by using FPGA, specifically designed to handle fringe jumps in the Hydrogen Cyanide (HCN) laser interferometer on the EAST superconducting tokamak. The method is designed for phase demodulator using the Fast Fourier Transform (FFT) method at the front end. The method is better adapted for hardware implementation compared to complex mathematical analysis algorithms, like Field Programmable Gate Array (FPGA). The method has been applied to process the phase measurement results of the HCN laser interferometer on EAST in real-time. Electron density results show a good confidence on the fringe jump unwrapping method. Further possible application on other laser interferometers, like the POlarimeter-INTerferometer (POINT) system on EAST is also discussed.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139265892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-16DOI: 10.1088/2058-6272/ad0d52
Hong Chun Lee, C. H. Lim, Haw Jiunn Woo, Boon Tong Goh, Oi Hoong Chin, T. Tou
As the size of satellites are scaling down, low power and compact propulsion systems such as the Pulsed Plasma Thruster (PPT) are needed for stabilizing these miniature satellites in orbit. Most PPT systems have been operated at 2 J or more of discharge energy. In this work, the performance of a PPT with a side-fed, tongue-flared electrode configuration operated at a range of lower discharge energy of 0.5 to 2.5 J has been investigated. Ablation and charring of the Teflon propellant surface were analysed through Field Effect Scanning Electron Microscopy (FESEM) imaging and Energy Dispersive X-Ray (EDX) spectra. It was found that at discharge energy below 2 J, inconsistency in specific impulse and thrust efficiency resulted from the low mass bit measured. At energies more than 2 J, the performance parameters are compared and extensively discussed with other PPT systems of similar configuration.
{"title":"Performance of pulsed plasma thruster at low discharge energy","authors":"Hong Chun Lee, C. H. Lim, Haw Jiunn Woo, Boon Tong Goh, Oi Hoong Chin, T. Tou","doi":"10.1088/2058-6272/ad0d52","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d52","url":null,"abstract":"As the size of satellites are scaling down, low power and compact propulsion systems such as the Pulsed Plasma Thruster (PPT) are needed for stabilizing these miniature satellites in orbit. Most PPT systems have been operated at 2 J or more of discharge energy. In this work, the performance of a PPT with a side-fed, tongue-flared electrode configuration operated at a range of lower discharge energy of 0.5 to 2.5 J has been investigated. Ablation and charring of the Teflon propellant surface were analysed through Field Effect Scanning Electron Microscopy (FESEM) imaging and Energy Dispersive X-Ray (EDX) spectra. It was found that at discharge energy below 2 J, inconsistency in specific impulse and thrust efficiency resulted from the low mass bit measured. At energies more than 2 J, the performance parameters are compared and extensively discussed with other PPT systems of similar configuration.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139267514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Interpreting experimental diagnostics data in tokamaks, which accounts for non-ideal effects, is challenging due to the complexity of plasmas. To address this challenge, a general synthetic diagnostics (GSD) platform that serves for microwave imaging reflectometer (MIR) and electron cyclotron emission imaging (ECEI) has been established. This platform utilizes plasma profiles as input, and it incorporates finite difference time domain (FDTD), ray-tracing and radiative transfer equation to calculate the propagation of plasma spontaneous radiation and external electromagnetic field in plasmas. Benchmarks of classic cases have been conducted to verify the accuracy of every core module in GSD platform. Finally, a 2D imaging of a typical electron temperature distribution is reproduced by this platform and is consistent with the given real experimental data. This platform also has potential to be extended to 3D electromagnetic field simulations and to other microwave diagnostics such as cross-polarization scattering.
{"title":"A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks","authors":"Zihan Li, Shangchuan Yang, Xinhang Xu, Lifu Zhang, C. Qu, Chengpu Li, Zhuang Ge, Jinlin Xie","doi":"10.1088/2058-6272/ad0d4c","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d4c","url":null,"abstract":"Interpreting experimental diagnostics data in tokamaks, which accounts for non-ideal effects, is challenging due to the complexity of plasmas. To address this challenge, a general synthetic diagnostics (GSD) platform that serves for microwave imaging reflectometer (MIR) and electron cyclotron emission imaging (ECEI) has been established. This platform utilizes plasma profiles as input, and it incorporates finite difference time domain (FDTD), ray-tracing and radiative transfer equation to calculate the propagation of plasma spontaneous radiation and external electromagnetic field in plasmas. Benchmarks of classic cases have been conducted to verify the accuracy of every core module in GSD platform. Finally, a 2D imaging of a typical electron temperature distribution is reproduced by this platform and is consistent with the given real experimental data. This platform also has potential to be extended to 3D electromagnetic field simulations and to other microwave diagnostics such as cross-polarization scattering.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139269950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision (PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons, and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value, when the number of gas atoms desorbed by an incident electron is taken as 0.4.
{"title":"Effect of desorbed gas on microwave breakdown on vacuum side of dielectric window","authors":"Pengcheng Zhao, Zhongyu Liu, Rui Wang, Panpan Shu, Lixing Guo, Xiangxin Cao","doi":"10.1088/2058-6272/ad0d58","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d58","url":null,"abstract":"The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision (PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons, and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value, when the number of gas atoms desorbed by an incident electron is taken as 0.4.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139267778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electron cyclotron emission diagnostic (ECE) system has been developed on ENN Spherical Torus (EXL-50). The ECE system aims to detect radiation from energetic electrons in the frequency range from 4 to 40 GHz. The system is composed of five subsystems with different frequency bands, i.e., C-band (4-8 GHz), X-band (8-12 GHz), Ku-band (12-18 GHz), K-band (18- 26.5 GHz) and Kα-band (26.4-40 GHz), and it using heterodyne detection. K-band and Kα-band subsystems are located horizontally in the EXL-50 equatorial plane while C-band, X-band and Ku-band subsystems are vertically located under EXL-50 vacuum vessel. The quasi-optical system has been developed to direct the microwaves from plasma to the antennas for horizontal detection subsystems. The antennas for vertical detection are attached directly to the port beneath the torus at R=700mm, i.e., the magnetic axis of the torus. The system integration, bench test and the initial experimental results will be given in detail.
电子回旋加速器发射诊断（ECE）系统是在 ENN 球形环（EXL-50）上开发的。该系统旨在探测频率范围为 4 至 40 千兆赫的高能电子辐射。该系统由五个不同频段的子系统组成，即 C 波段（4-8 千兆赫）、X 波段（8-12 千兆赫）、Ku 波段（12-18 千兆赫）、K 波段（18-26.5 千兆赫）和 Kα 波段（26.4-40 千兆赫），并采用外差探测技术。K 波段和 Kα 波段子系统水平安装在 EXL-50 的赤道平面上，而 C 波段、X 波段和 Ku 波段子系统则垂直安装在 EXL-50 的真空容器下。已开发出准光学系统，将等离子体的微波引向水平探测子系统的天线。用于垂直探测的天线直接连接到环体下方 R=700mm 处的端口，即环体的磁轴。将详细介绍系统集成、台架测试和初步实验结果。
{"title":"Design of the electron cyclotron emission diagnostic on EXL-50 spherical torus","authors":"Yumin Wang, Qifeng Xie, Renyi Tao, Hui Zhang, Xiaokun Bo, Tiantian Sun, Xiuchun Lun, Lin Chen, Dong Guo, Bihe Deng, Minsheng Liu","doi":"10.1088/2058-6272/ad0d54","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d54","url":null,"abstract":"The electron cyclotron emission diagnostic (ECE) system has been developed on ENN Spherical Torus (EXL-50). The ECE system aims to detect radiation from energetic electrons in the frequency range from 4 to 40 GHz. The system is composed of five subsystems with different frequency bands, i.e., C-band (4-8 GHz), X-band (8-12 GHz), Ku-band (12-18 GHz), K-band (18- 26.5 GHz) and Kα-band (26.4-40 GHz), and it using heterodyne detection. K-band and Kα-band subsystems are located horizontally in the EXL-50 equatorial plane while C-band, X-band and Ku-band subsystems are vertically located under EXL-50 vacuum vessel. The quasi-optical system has been developed to direct the microwaves from plasma to the antennas for horizontal detection subsystems. The antennas for vertical detection are attached directly to the port beneath the torus at R=700mm, i.e., the magnetic axis of the torus. The system integration, bench test and the initial experimental results will be given in detail.","PeriodicalId":20250,"journal":{"name":"Plasma Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139268668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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