Pub Date : 2024-05-21DOI: 10.1088/2058-6272/ad4e79
Chenxue Wang, Rong Yan, Yuming Liu, Su Xu, Lei Mu, Wei Zheng, Rui Ding, Junling Chen
The first mirror (FM) cleaning, using radio frequency plasma, has been proposed to recover the FM reflectivity in nuclear fusion reactors such as ITER. To investigate the influence of simultaneous cleaning of two mirrors on mirror cleaning efficiency and uniformity, experiments involving single-mirror cleaning and dual-mirror cleaning were conducted using radio frequency (RF) capacitively coupled plasma in the laboratory. For the test and simultaneous cleaning of two mirrors, the FM and second mirror (SM), both measuring 110 × 80 mm2, were placed inside the first mirror unit (FMU). They were composed of 16 mirror samples with a dimension of 27.5 × 20 mm2 each. These mirror samples consist of a titanium-zirconium-molybdenum (TZM) alloy substrate, a 500 nm molybdenum intermediate layer, and a 30 nm aluminum oxide (Al2O3) surface coating as a proxy for Be impurities. The cleaning of a single first mirror (SFM) and the simultaneous cleaning of FM and SM (DFM and DSM) were lasted for 9 h using argon (Ar) plasma at a pressure of 1 Pa. The total reflectivity of mirror samples on the DSM did not fully recover and varied with locations with a self-bias of −140 V. While with a self-bias of −300 V, the total reflectivity of mirror samples on SFM and DFM was fully recovered. The energy dispersive spectrometer (EDS) results demonstrated that the Al2O3 coating had been completely removed from these mirror samples. However, the mass loss of each mirror sample on SFM and DFM before and after cleaning varied depending on their locations, with higher mass loss observed for mirror samples located in the corners and lower for those in the center. Compared to the single mirror cleaning, the simultaneous cleaning of two mirrors reduced the difference of the mass loss between the highest and lowest. Furthermore, this mass loss for the mirror samples of DFM facing the DSM was increased. It indicated that the simultaneous cleaning of mirror samples face to face in the FMU could influence each other, highlighting the necessity for special attention in future studies.
{"title":"Cleaning of two mirrors in first mirror unit using radio frequency capacitively coupled plasma","authors":"Chenxue Wang, Rong Yan, Yuming Liu, Su Xu, Lei Mu, Wei Zheng, Rui Ding, Junling Chen","doi":"10.1088/2058-6272/ad4e79","DOIUrl":"https://doi.org/10.1088/2058-6272/ad4e79","url":null,"abstract":"\u0000 The first mirror (FM) cleaning, using radio frequency plasma, has been proposed to recover the FM reflectivity in nuclear fusion reactors such as ITER. To investigate the influence of simultaneous cleaning of two mirrors on mirror cleaning efficiency and uniformity, experiments involving single-mirror cleaning and dual-mirror cleaning were conducted using radio frequency (RF) capacitively coupled plasma in the laboratory. For the test and simultaneous cleaning of two mirrors, the FM and second mirror (SM), both measuring 110 × 80 mm2, were placed inside the first mirror unit (FMU). They were composed of 16 mirror samples with a dimension of 27.5 × 20 mm2 each. These mirror samples consist of a titanium-zirconium-molybdenum (TZM) alloy substrate, a 500 nm molybdenum intermediate layer, and a 30 nm aluminum oxide (Al2O3) surface coating as a proxy for Be impurities. The cleaning of a single first mirror (SFM) and the simultaneous cleaning of FM and SM (DFM and DSM) were lasted for 9 h using argon (Ar) plasma at a pressure of 1 Pa. The total reflectivity of mirror samples on the DSM did not fully recover and varied with locations with a self-bias of −140 V. While with a self-bias of −300 V, the total reflectivity of mirror samples on SFM and DFM was fully recovered. The energy dispersive spectrometer (EDS) results demonstrated that the Al2O3 coating had been completely removed from these mirror samples. However, the mass loss of each mirror sample on SFM and DFM before and after cleaning varied depending on their locations, with higher mass loss observed for mirror samples located in the corners and lower for those in the center. Compared to the single mirror cleaning, the simultaneous cleaning of two mirrors reduced the difference of the mass loss between the highest and lowest. Furthermore, this mass loss for the mirror samples of DFM facing the DSM was increased. It indicated that the simultaneous cleaning of mirror samples face to face in the FMU could influence each other, highlighting the necessity for special attention in future studies.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"30 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141113742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-21DOI: 10.1088/2058-6272/ad4e78
Debing Zhang, Pengfei Zhao, Yingfeng Xu, Lei Ye, Xianmei Zhang
The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the ITER baseline scenario. The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron (ae) model and the fully drift-kinetic electron (ke) model in the NLT code, respectively. The linear simulations focus on the dependence of linear frequency on the plasma parameters, such as the ion and electron temperature gradients κT i,e≡R/LTi,e , the density gradient κn≡R/Ln, and the ion-electron temperature ratio τ=Te/Ti with Te and Ti the electron and ion temperatures, respectively. Here, R is the major radius, LA=(-∂rln A)-1 denotes the gradient scale length. In the ke model, the ion temperature gradient (ITG) instability and the trapped electron mode (TEM) dominate in the small and large kθ region, respectively, where kθ is the poloidal wavenumber. The TEM-dominant region becomes wider by increasing (decreasing) κT e (κT i) or by decreasing κn. For the nominal parameters of ITER baseline scenario, the maximum growth rate of dominant ITG instability in the ke model is about 3 times larger than that in the ae model. The normalized linear frequency depends on the value of τ, instead of the value of Te or Ti in both the ae and ke models. The nonlinear simulation results show that the ion heat diffusivity in the ke model is quite larger than that in the ae model, the radial structure is finer and the time oscillation is more rapid. Besides, the magnitude of fluctuated potential at the saturated stage peaks in the ITG-dominated region, contributions from the TEM dominated in higher kθ region to the nonlinear transport can be neglected. The zonal radial electric field is found to be mainly driven by the turbulent energy flux, the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect. The mechanism of turbulence-driven zonal radial electric field is not affected by the kinetic electron effects.
根据热核实验堆基线方案，使用陀螺动力学代码 NLT 对氘等离子体核心区域的静电不稳定性进行了线性和非线性模拟。通过在 NLT 代码中分别采用绝热电子（ae）模型和全漂移动能电子（ke）模型，研究了动能电子对线性频率和非线性传输的影响。线性模拟的重点是线性频率与等离子体参数的关系，如离子和电子温度梯度κT i,e≡R/LTi,e，密度梯度κn≡R/Ln，以及离子-电子温度比τ=Te/Ti，其中Te和Ti分别为电子和离子温度。这里，R 是主半径，LA=（-∂rln A）-1 表示梯度尺度长度。在 ke 模型中，离子温度梯度（ITG）不稳定性和受困电子模式（TEM）分别在小 kθ 和大 kθ 区域占主导地位，其中 kθ 是极波波长。随着 κT e (κT i) 的增大（减小）或 κn 的减小，TEM 主导区域会变得更宽。对于热核实验堆基线方案的标称参数，ke 模型中主导 ITG 不稳定性的最大增长率约为 ae 模型的 3 倍。在 ae 和 ke 模型中，归一化线性频率取决于 τ 值，而不是 Te 或 Ti 值。非线性模拟结果表明，ke 模型中的离子热扩散率比 ae 模型中的大，径向结构更精细，时间振荡更迅速。此外，饱和阶段的波动电势在 ITG 主导区域达到峰值，可以忽略高 kθ 区域的 TEM 主导对非线性输运的贡献。带状径向电场主要由湍流能量通量驱动，由于环形屏蔽效应，湍流极性雷诺应力的贡献很小。湍流驱动的带状径向电场机制不受电子动力学效应的影响。
{"title":"Gyrokinetic simulations of the kinetic electron effects on the electrostatic instabilities on the ITER baseline scenario","authors":"Debing Zhang, Pengfei Zhao, Yingfeng Xu, Lei Ye, Xianmei Zhang","doi":"10.1088/2058-6272/ad4e78","DOIUrl":"https://doi.org/10.1088/2058-6272/ad4e78","url":null,"abstract":"\u0000 The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the ITER baseline scenario. The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron (ae) model and the fully drift-kinetic electron (ke) model in the NLT code, respectively. The linear simulations focus on the dependence of linear frequency on the plasma parameters, such as the ion and electron temperature gradients κT\u0000 i,e≡R/LTi,e\u0000 , the density gradient κn≡R/Ln, and the ion-electron temperature ratio τ=Te/Ti with Te and Ti the electron and ion temperatures, respectively. Here, R is the major radius, LA=(-∂rln A)-1 denotes the gradient scale length. In the ke model, the ion temperature gradient (ITG) instability and the trapped electron mode (TEM) dominate in the small and large kθ region, respectively, where kθ is the poloidal wavenumber. The TEM-dominant region becomes wider by increasing (decreasing) κT\u0000 e (κT\u0000 i) or by decreasing κn. For the nominal parameters of ITER baseline scenario, the maximum growth rate of dominant ITG instability in the ke model is about 3 times larger than that in the ae model. The normalized linear frequency depends on the value of τ, instead of the value of Te or Ti in both the ae and ke models. The nonlinear simulation results show that the ion heat diffusivity in the ke model is quite larger than that in the ae model, the radial structure is finer and the time oscillation is more rapid. Besides, the magnitude of fluctuated potential at the saturated stage peaks in the ITG-dominated region, contributions from the TEM dominated in higher kθ region to the nonlinear transport can be neglected. The zonal radial electric field is found to be mainly driven by the turbulent energy flux, the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect. The mechanism of turbulence-driven zonal radial electric field is not affected by the kinetic electron effects.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"18 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141117148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-16DOI: 10.1088/2058-6272/ad4cad
Li Sun, Zhuo Dai, Ming Xu, Wei Wang, Zeng-Yao Li
Electrons can escape from the cathode surface by acquiring enough energy greater than the work function or weakening the potential barrier at the cathode surface through tunneling effects in gas discharges, which plays a dominant role in the plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications. It is necessary to illustrate the various electron emission mechanisms and corresponding applicable description models to evaluate the impacts on discharge properties, especially for numerical simulation studies. However, most current researches usually rely on previous experience to select the appropriate simplified formula to calculate the electron emission current density, and there is little work that can explicitly give the application range of the simplified formulas for describing electron emission. In this work, the detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed, and corresponding application ranges are determined in the framework of the Murphy-Good theory, which is commonly regarded as the general model and to be accurate in the full range of conditions of validity of the theory. The dimensionless parametrization is used to evaluate the emission current density of the Murphy-Good formula and a deviation factor is defined to obtain the application ranges for different work functions (2.5~5 eV), different cathode temperatures (300~6000 K), and different emitted electric field (105 ~1010 V‧m-1). The deviation factor is shown to be a non-monotonic function of the three parameters. A comparative study of particle number densities in atmospheric gas discharge with tungsten cathode is performed based on the one-dimensional implicit particle-in-cell with the Monte Carlo Collision (PIC-MCC) method according to the above application ranges. It is found that small differences in emission current density can lead to variation in the distributions of particle number density due to the change of collisional environment. This present work can provide a theoretical basis to select emission models for the subsequent numerical simulation.
{"title":"Analysis of application range of simplified models for field to thermo-field to thermionic emission processes from the cathode","authors":"Li Sun, Zhuo Dai, Ming Xu, Wei Wang, Zeng-Yao Li","doi":"10.1088/2058-6272/ad4cad","DOIUrl":"https://doi.org/10.1088/2058-6272/ad4cad","url":null,"abstract":"\u0000 Electrons can escape from the cathode surface by acquiring enough energy greater than the work function or weakening the potential barrier at the cathode surface through tunneling effects in gas discharges, which plays a dominant role in the plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications. It is necessary to illustrate the various electron emission mechanisms and corresponding applicable description models to evaluate the impacts on discharge properties, especially for numerical simulation studies. However, most current researches usually rely on previous experience to select the appropriate simplified formula to calculate the electron emission current density, and there is little work that can explicitly give the application range of the simplified formulas for describing electron emission. In this work, the detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed, and corresponding application ranges are determined in the framework of the Murphy-Good theory, which is commonly regarded as the general model and to be accurate in the full range of conditions of validity of the theory. The dimensionless parametrization is used to evaluate the emission current density of the Murphy-Good formula and a deviation factor is defined to obtain the application ranges for different work functions (2.5~5 eV), different cathode temperatures (300~6000 K), and different emitted electric field (105 ~1010 V‧m-1). The deviation factor is shown to be a non-monotonic function of the three parameters. A comparative study of particle number densities in atmospheric gas discharge with tungsten cathode is performed based on the one-dimensional implicit particle-in-cell with the Monte Carlo Collision (PIC-MCC) method according to the above application ranges. It is found that small differences in emission current density can lead to variation in the distributions of particle number density due to the change of collisional environment. This present work can provide a theoretical basis to select emission models for the subsequent numerical simulation.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140967109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-09DOI: 10.1088/2058-6272/ad495f
Naoko Ashikawa, R. Lunsford, Federico Nespoli, E. Gilson, S. Kado, Jiansheng Hu, Yaowei Yu
In Large Helical Device (LHD), diborane (B2H6) is used as a standard boron source for boronization, which is assisted by helium glow discharges. In 2019, a new Impurity Powder Dropper (IPD) system has been installed and is under evaluation as a real-time wall conditioning technique. In LHD), which is a large size heliotron device, an additional helium (He) glow discharge cleaning (GDC) after boronization has been operated for a reduction of hydrogen recycling from coated boron layers, and this operational time of 3 h was determined by spectroscopic data during glow discharges. A flat hydrogen profile is obtained on the top surface of coated boron on the specimen exposed to boronization, the result suggests a reduction of hydrogen at the top surface by He-GDC. Trapped oxygen in coated boron was obtained by boronization, and the coated boron, which has boron-oxide, on the first wall by B-IPD was also shown. Considering the difference in coating areas between B2H6 boronization and B-IPD operation, it would be most effective to use the IPD and B2H6 boronization coating together for optimized wall conditioning.
{"title":"Coated boron layers by boronization and a real-time boron coating using impurity powder dropper in LHD","authors":"Naoko Ashikawa, R. Lunsford, Federico Nespoli, E. Gilson, S. Kado, Jiansheng Hu, Yaowei Yu","doi":"10.1088/2058-6272/ad495f","DOIUrl":"https://doi.org/10.1088/2058-6272/ad495f","url":null,"abstract":"\u0000 In Large Helical Device (LHD), diborane (B2H6) is used as a standard boron source for boronization, which is assisted by helium glow discharges. In 2019, a new Impurity Powder Dropper (IPD) system has been installed and is under evaluation as a real-time wall conditioning technique. In LHD), which is a large size heliotron device, an additional helium (He) glow discharge cleaning (GDC) after boronization has been operated for a reduction of hydrogen recycling from coated boron layers, and this operational time of 3 h was determined by spectroscopic data during glow discharges. A flat hydrogen profile is obtained on the top surface of coated boron on the specimen exposed to boronization, the result suggests a reduction of hydrogen at the top surface by He-GDC. Trapped oxygen in coated boron was obtained by boronization, and the coated boron, which has boron-oxide, on the first wall by B-IPD was also shown. Considering the difference in coating areas between B2H6 boronization and B-IPD operation, it would be most effective to use the IPD and B2H6 boronization coating together for optimized wall conditioning.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140995016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Discharge plasma parameter measurement is a key focus in low-temperature plasma research. Traditional diagnostics often require costly equipment, whereas electro-acoustic signals provide a rich, non-invasive, and less complex source of discharge information. This study harnesses machine learning to decode these signals. It establishes links between electro-acoustic signals and gas discharge parameters, such as power and distance, thus streamlining the prediction process. By building a spark discharge platform to collect electro-acoustic signals and implementing a series of acoustic signal processing techniques, the Mel-Frequency Cepstral Coefficients (MFCCs) of the acoustic signals are extracted to construct the predictors. Three machine learning models (Linear Regression, k-Nearest Neighbors, and Random Forest) are introduced and applied to the predictors to achieve real-time rapid diagnostic measurement of typical spark discharge power and discharge distance. All models display impressive performance in prediction precision and fitting abilities. Among them, the k-Nearest Neighbors model shows the best performance on discharge power prediction with the lowest mean square error (MSE=0.00571) and the highest R-squared value (R^2=0.93877). The experimental results show that the relationship between the electro-acoustic signal and the gas discharge power and distance can be effectively constructed based on the machine learning algorithm, which provides a new idea and basis for the online monitoring and real-time diagnosis of plasma parameters.
{"title":"Machine learning for parameters diagnosis of spark discharge by electro-acoustic signal","authors":"Jun Xiong, Shiyu Lu, Xiaoming Liu, Wenjun Zhou, Xiaoming Zha, Xuekai Pei","doi":"10.1088/2058-6272/ad495e","DOIUrl":"https://doi.org/10.1088/2058-6272/ad495e","url":null,"abstract":"\u0000 Discharge plasma parameter measurement is a key focus in low-temperature plasma research. Traditional diagnostics often require costly equipment, whereas electro-acoustic signals provide a rich, non-invasive, and less complex source of discharge information. This study harnesses machine learning to decode these signals. It establishes links between electro-acoustic signals and gas discharge parameters, such as power and distance, thus streamlining the prediction process. By building a spark discharge platform to collect electro-acoustic signals and implementing a series of acoustic signal processing techniques, the Mel-Frequency Cepstral Coefficients (MFCCs) of the acoustic signals are extracted to construct the predictors. Three machine learning models (Linear Regression, k-Nearest Neighbors, and Random Forest) are introduced and applied to the predictors to achieve real-time rapid diagnostic measurement of typical spark discharge power and discharge distance. All models display impressive performance in prediction precision and fitting abilities. Among them, the k-Nearest Neighbors model shows the best performance on discharge power prediction with the lowest mean square error (MSE=0.00571) and the highest R-squared value (R^2=0.93877). The experimental results show that the relationship between the electro-acoustic signal and the gas discharge power and distance can be effectively constructed based on the machine learning algorithm, which provides a new idea and basis for the online monitoring and real-time diagnosis of plasma parameters.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140995471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-08DOI: 10.1088/2058-6272/ad48cf
Xingqiang Lu, Ge Gao, Zhiwei Ma, Wei Guo, X. Li
The CLT code is used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of m/n = 3/1 double tearing mode. This work focuses on the explosive reconnection processes in which energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small qmin (the minimum value of safety factor), or a low resistivity. The relationships between the higher m and n modes development, explosive reconnection rate and the position exchange of 3/1 islands are summarized for the first time. The separation plays a more important role than qmin on enhancing the development of higher m and n modes. At a relatively large separation, the well development of higher m and n modes greatly reduces the reconnection rate, and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.
CLT 代码用于定量研究环模耦合对 m/n = 3/1 双撕裂模式爆炸动力学的影响。这项工作的重点是爆炸性再连接过程，在这个过程中，当两个有理面之间的距离在中等范围内相对较大时，能量爆发，主模式不再占主导地位。两个有理面之间相对较大的间隔、较小的 qmin（安全系数的最小值）或较低的电阻率，都有利于较高 m 和 n 模式的发展。本文首次总结了高m模和高n模的发展、爆炸重联率和3/1岛位置交换之间的关系。在促进高m模和n模的发展方面，分离度比qmin起着更重要的作用。在相对较大的分离度下，高m模和高n模的良好发展会大大降低重联率，并抑制主模的发展，导致主模无法发展到足够大的程度以产生3/1岛的位置变化。
{"title":"Effect of toroidal mode coupling on explosive dynamics of m/n=3/1 double tearing mode","authors":"Xingqiang Lu, Ge Gao, Zhiwei Ma, Wei Guo, X. Li","doi":"10.1088/2058-6272/ad48cf","DOIUrl":"https://doi.org/10.1088/2058-6272/ad48cf","url":null,"abstract":"\u0000 The CLT code is used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of m/n = 3/1 double tearing mode. This work focuses on the explosive reconnection processes in which energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small qmin (the minimum value of safety factor), or a low resistivity. The relationships between the higher m and n modes development, explosive reconnection rate and the position exchange of 3/1 islands are summarized for the first time. The separation plays a more important role than qmin on enhancing the development of higher m and n modes. At a relatively large separation, the well development of higher m and n modes greatly reduces the reconnection rate, and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141001287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-08DOI: 10.1088/2058-6272/ad48d0
Yuqiang Zhang, Xingang Yu, Zongbiao Ye
Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV induced hydrogen plasma. Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impact on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium coating of mirrors creates a positively charged wall and then prevents the ion from impacting onto the mirror and therefore changes the flux and energy distribution of ions reach the mirror. Furthermore, gas pressure has notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and the energy corresponding to the peak flux decreases slightly in the meantime. Meanwhile, EUV source intensity barely changes the sheath potential and its influence on the ion impact is mainly limited to the approximate linear increase of ion flux.
{"title":"Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror","authors":"Yuqiang Zhang, Xingang Yu, Zongbiao Ye","doi":"10.1088/2058-6272/ad48d0","DOIUrl":"https://doi.org/10.1088/2058-6272/ad48d0","url":null,"abstract":"\u0000 Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV induced hydrogen plasma. Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impact on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium coating of mirrors creates a positively charged wall and then prevents the ion from impacting onto the mirror and therefore changes the flux and energy distribution of ions reach the mirror. Furthermore, gas pressure has notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and the energy corresponding to the peak flux decreases slightly in the meantime. Meanwhile, EUV source intensity barely changes the sheath potential and its influence on the ion impact is mainly limited to the approximate linear increase of ion flux.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":" 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140999633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.1088/2058-6272/ad47df
An Mao, Zhifeng Cheng, Bo Rao, Jingmin Yang, Ming Zhang
An advanced spectral diagnostic system has been developed to measure the electron temperature (Te), elec-tron density (Ne), and ion temperature (Ti) for the Huazhong University of Science and Technology (HUST) field-reversed configuration (HFRC) plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny-Turner (C-T) monochromator equipped with both a 3600 g/ mm−1 grating and a 2400 g /mm−1 grating to achieve the measurement of line spectrum. Accompanying these components is an Electron-Multiplying Charge-coupled Device (EMCCD) camera to capture the spectral data. The relative intensity of the optical fiber spectrometer has been calibrated using a standard luminance source, and the spectrometer’'s wavelength calibration has been accomplished by a mercury argon lamp. This diagnostic setup has been configured to measure the electron density based on the Stark effect of Hγ (n = 5 → n = 2, 434.04 nm). Doppler broadening of an O III (2s22p(2P°)3p → 2s22p(2P°)3s, 375.988 nm) emission line is measured and analyszed to obtain the ion temperature, electron temperatures can be estimated from the relative strength of Hβ (n = 4 → n = 2, 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density is obtained from Stark effect measurements. Initial experimental results indicate that the highest electron temperature of the formation region is around 8 eV; the electron density of the col-liding-and-merging region is approaching 1020 m−-3 and the ion temperature reaches about 40 eV.
{"title":"A first spectroscopic study of HFRC plasma","authors":"An Mao, Zhifeng Cheng, Bo Rao, Jingmin Yang, Ming Zhang","doi":"10.1088/2058-6272/ad47df","DOIUrl":"https://doi.org/10.1088/2058-6272/ad47df","url":null,"abstract":"\u0000 An advanced spectral diagnostic system has been developed to measure the electron temperature (Te), elec-tron density (Ne), and ion temperature (Ti) for the Huazhong University of Science and Technology (HUST) field-reversed configuration (HFRC) plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny-Turner (C-T) monochromator equipped with both a 3600 g/ mm−1 grating and a 2400 g /mm−1 grating to achieve the measurement of line spectrum. Accompanying these components is an Electron-Multiplying Charge-coupled Device (EMCCD) camera to capture the spectral data. The relative intensity of the optical fiber spectrometer has been calibrated using a standard luminance source, and the spectrometer’'s wavelength calibration has been accomplished by a mercury argon lamp. This diagnostic setup has been configured to measure the electron density based on the Stark effect of Hγ (n = 5 → n = 2, 434.04 nm). Doppler broadening of an O III (2s22p(2P°)3p → 2s22p(2P°)3s, 375.988 nm) emission line is measured and analyszed to obtain the ion temperature, electron temperatures can be estimated from the relative strength of Hβ (n = 4 → n = 2, 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density is obtained from Stark effect measurements. Initial experimental results indicate that the highest electron temperature of the formation region is around 8 eV; the electron density of the col-liding-and-merging region is approaching 1020 m−-3 and the ion temperature reaches about 40 eV.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"17 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141008113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.1088/2058-6272/ad47db
Yue Li, Nan Jiang, Zhengyan Liu, Liang Qin, Bangfa Peng, Ronggang Wang, Yurong Sun, Jie Li
Dielectric barrier discharge (DBD) plasma excited by high-frequency alternating-current (AC) power supply is widely employed for the degradation of volatile organic compounds (VOCs). However, the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency. In this work, an innovative DBD thermal-conducted catalysis (DBD-TCC) system, integrating high-frequency AC-DBD plasma and its generated thermal effect to activate the Co/SBA-15 catalyst, was employed for toluene removal. Specifically, Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 kV. At 12.4 kV, the temperature in the catalyst zone could reach 261 °C in the DBD-TCC system, resulting in an increase in toluene degradation efficiency of 17%, CO2 selectivity of 21.2%, and energy efficiency of 27%, respectively, compared to the DBD system alone. In contrast, the DBD thermal-unconducted catalysis (DBD-TUC) system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation, highlighting the crucial role of AC-DBD generated heat in activating the catalyst. Furthermore, the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized. This work is expected to provide an energy-efficiency approach for high-frequency AC-DBD plasma removal of VOCs.
{"title":"Efficient activation of Co/SBA-15 catalyst by high-frequency AC-DBD plasma thermal effect for toluene removal","authors":"Yue Li, Nan Jiang, Zhengyan Liu, Liang Qin, Bangfa Peng, Ronggang Wang, Yurong Sun, Jie Li","doi":"10.1088/2058-6272/ad47db","DOIUrl":"https://doi.org/10.1088/2058-6272/ad47db","url":null,"abstract":"\u0000 Dielectric barrier discharge (DBD) plasma excited by high-frequency alternating-current (AC) power supply is widely employed for the degradation of volatile organic compounds (VOCs). However, the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency. In this work, an innovative DBD thermal-conducted catalysis (DBD-TCC) system, integrating high-frequency AC-DBD plasma and its generated thermal effect to activate the Co/SBA-15 catalyst, was employed for toluene removal. Specifically, Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 kV. At 12.4 kV, the temperature in the catalyst zone could reach 261 °C in the DBD-TCC system, resulting in an increase in toluene degradation efficiency of 17%, CO2 selectivity of 21.2%, and energy efficiency of 27%, respectively, compared to the DBD system alone. In contrast, the DBD thermal-unconducted catalysis (DBD-TUC) system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation, highlighting the crucial role of AC-DBD generated heat in activating the catalyst. Furthermore, the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized. This work is expected to provide an energy-efficiency approach for high-frequency AC-DBD plasma removal of VOCs.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"17 s2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141008775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-12DOI: 10.1088/2058-6272/ad3e47
Yunkai Cai, Bingfeng Huang, Fei Dong, Neng Zhu
Seagoing vessels are responsible for more than 90% of global freight traffic, but meanwhile, emission pollutants (NOx and SOx) of seagoing vessels also cause serious air pollution. Nonthermal plasma (NTP) combined with wet scrubbing technology is considered to be a promising technology. In order to improve the oxidation efficiency and energy efficiency of the NTP reactor, the screw and rod inner electrodes of dielectric barrier discharge (DBD) reactor were investigated. To analyze the mechanism, the optical emission spectra (OES) of NTP was measured and numerical calculation was applied. The experiment results show that the NO oxidation removal efficiency of screw electrode is lower than that of rod electrode. However, the SO2 removal efficiency of screw electrode is higher. According to the OES experiment and numerical calculation, the electric field intensity of the screw electrode surface is much higher than that of the rod electrode surface, and it is easier to generate N radicals to form NO. For the same energy density condition, the OH radical generation efficiency of the screw electrode reactor is similar to that of the rod electrode, but the gas temperature in the discharge gap is higher. Therefore, the SO2 oxidation efficiency of the thread electrode is higher. This study provides guidance for the optimization of oxidation efficiency and energy consumption of DBD reactor.
海轮承担着全球 90% 以上的货运量，但与此同时，海轮排放的污染物（氮氧化物和硫氧化物）也造成了严重的空气污染。非热等离子体（NTP）与湿式洗涤技术相结合被认为是一种前景广阔的技术。为了提高 NTP 反应器的氧化效率和能效，研究人员对介质阻挡放电（DBD）反应器的螺杆和杆内电极进行了研究。为分析其机理，测量了 NTP 的光发射光谱（OES）并进行了数值计算。实验结果表明，螺旋电极的 NO 氧化去除效率低于棒状电极。然而，螺旋电极对二氧化硫的去除效率较高。根据 OES 实验和数值计算，螺旋电极表面的电场强度远高于棒状电极表面，更容易产生 N 自由基生成 NO。在相同能量密度条件下，螺旋电极反应器的 OH 自由基生成效率与棒状电极相似，但放电间隙中的气体温度更高。因此，螺纹电极的 SO2 氧化效率更高。这项研究为优化 DBD 反应器的氧化效率和能耗提供了指导。
{"title":"The effects of inner electrode shape on the performance of dielectric barrier discharge reactor for oxidative removal of NO and SO2","authors":"Yunkai Cai, Bingfeng Huang, Fei Dong, Neng Zhu","doi":"10.1088/2058-6272/ad3e47","DOIUrl":"https://doi.org/10.1088/2058-6272/ad3e47","url":null,"abstract":"\u0000 Seagoing vessels are responsible for more than 90% of global freight traffic, but meanwhile, emission pollutants (NOx and SOx) of seagoing vessels also cause serious air pollution. Nonthermal plasma (NTP) combined with wet scrubbing technology is considered to be a promising technology. In order to improve the oxidation efficiency and energy efficiency of the NTP reactor, the screw and rod inner electrodes of dielectric barrier discharge (DBD) reactor were investigated. To analyze the mechanism, the optical emission spectra (OES) of NTP was measured and numerical calculation was applied. The experiment results show that the NO oxidation removal efficiency of screw electrode is lower than that of rod electrode. However, the SO2 removal efficiency of screw electrode is higher. According to the OES experiment and numerical calculation, the electric field intensity of the screw electrode surface is much higher than that of the rod electrode surface, and it is easier to generate N radicals to form NO. For the same energy density condition, the OH radical generation efficiency of the screw electrode reactor is similar to that of the rod electrode, but the gas temperature in the discharge gap is higher. Therefore, the SO2 oxidation efficiency of the thread electrode is higher. This study provides guidance for the optimization of oxidation efficiency and energy consumption of DBD reactor.","PeriodicalId":506986,"journal":{"name":"Plasma Science and Technology","volume":"104 S11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140709107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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