Pub Date : 2023-11-16DOI: 10.1088/2058-6272/ad0d4a
P. Micozzi, Franco Alladio, Alessandro Mancuso, V. Zanza, Gerarda Apruzzese, Francesca Bombarda, Luca Boncagni, Paolo Buratti, Francesco Filippi, Giuseppe Galatola Teka, Francesco Giammanco, E. Giovannozzi, A. Grosso, M. Iafrati, A. Lampasi, V. Lazic, S. Magagnino, Simone Mannori, Paolo Marsili, V. Piergotti, Giuliano Rocchi, A. Sibio, B. Tilia, O. Tudisco
In astrophysics the boundary conditions for plasma phenomena are provided by nature and the astronomer faces the problem of understanding them from a variety of observations [Hester J J et al], on the other hand in laboratory plasma experiments the electromagnetic boundary conditions become a major problem in the set-up of the machine that produces the plasma, an issue that has to be investigated step by step and to be modified and adapted with great patience, in particular in the case of an innovative plasma confinement experiment. The PROTO-SPHERA machine [Alladio F et al] is a magnetic confinement experiment, that emulates in the laboratory the jet + torus plasma configurations often observed in astrophysics: an inner magnetized jet of plasma centered on the (approximate) axis of symmetry and surrounded by a magnetized plasma torus orthogonal to this jet. The PROTO-SPHERA plasma is simply connected, i.e., no metal current conducting rod is linked to the plasma torus, while instead it is the inner magnetized plasma jet (in the following always called the plasma centerpost) that is linked to the torus. It is mandatory that no spurious plasma current path modifies the optimal shape of the plasma centerpost. Moreover, as the plasma torus is produced and sustained, in absence of any applied inductive electric field, by the inner plasma centerpost through magnetic reconnections [Taylor J B and Turner M F], it is required as well that spurious current paths do not surround the torus on its outboard, in order not to lower the efficiency of the magnetic reconnections that maintain the plasma torus at the expense of the plasma centerpost. Boundary conditions have been corrected, up to the point that the first sustainment in steady state has been achieved for the combined plasma.
在天体物理学中，等离子体现象的边界条件由自然界提供，天文学家面临的问题是如何通过各种观测来理解这些边界条件[Hester J J et al]；另一方面，在实验室等离子体实验中，电磁边界条件成为产生等离子体的机器设置中的一个主要问题，这个问题必须逐步研究，并以极大的耐心进行修改和调整，特别是在创新等离子体约束实验中。PROTO-SPHERA 机器[Alladio F 等人]是一个磁约束实验，它在实验室中模拟了天体物理学中经常观察到的喷流+环形等离子体配置：以（近似）对称轴为中心的内磁化等离子体喷流，周围是与该喷流正交的磁化等离子体环。PROTO-SPHERA 等离子体的连接方式很简单，即没有金属导流棒与等离子体环相连，而是内部磁化等离子体喷流（下文中称为等离子体中心柱）与等离子体环相连。必须确保等离子体电流路径不会改变等离子体中心柱的最佳形状。此外，由于等离子体环是在没有任何外加感应电场的情况下，由内部等离子体中柱通过磁性再连接产生和维持的[泰勒-J-B 和特纳-M-F]，因此也要求等离子体环的外侧不被杂散电流路径包围，以免降低磁性再连接的效率，从而以等离子体中柱为代价维持等离子体环。对边界条件进行了修正，使组合等离子体首次实现了稳态维持。
{"title":"Final results of the first phase of the PROTO-SPHERA experiment: obtainment of the full current stable screw pinch and first evidences of the jet + torus combined plasma configuration","authors":"P. Micozzi, Franco Alladio, Alessandro Mancuso, V. Zanza, Gerarda Apruzzese, Francesca Bombarda, Luca Boncagni, Paolo Buratti, Francesco Filippi, Giuseppe Galatola Teka, Francesco Giammanco, E. Giovannozzi, A. Grosso, M. Iafrati, A. Lampasi, V. Lazic, S. Magagnino, Simone Mannori, Paolo Marsili, V. Piergotti, Giuliano Rocchi, A. Sibio, B. Tilia, O. Tudisco","doi":"10.1088/2058-6272/ad0d4a","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d4a","url":null,"abstract":"In astrophysics the boundary conditions for plasma phenomena are provided by nature and the astronomer faces the problem of understanding them from a variety of observations [Hester J J et al], on the other hand in laboratory plasma experiments the electromagnetic boundary conditions become a major problem in the set-up of the machine that produces the plasma, an issue that has to be investigated step by step and to be modified and adapted with great patience, in particular in the case of an innovative plasma confinement experiment. The PROTO-SPHERA machine [Alladio F et al] is a magnetic confinement experiment, that emulates in the laboratory the jet + torus plasma configurations often observed in astrophysics: an inner magnetized jet of plasma centered on the (approximate) axis of symmetry and surrounded by a magnetized plasma torus orthogonal to this jet. The PROTO-SPHERA plasma is simply connected, i.e., no metal current conducting rod is linked to the plasma torus, while instead it is the inner magnetized plasma jet (in the following always called the plasma centerpost) that is linked to the torus. It is mandatory that no spurious plasma current path modifies the optimal shape of the plasma centerpost. Moreover, as the plasma torus is produced and sustained, in absence of any applied inductive electric field, by the inner plasma centerpost through magnetic reconnections [Taylor J B and Turner M F], it is required as well that spurious current paths do not surround the torus on its outboard, in order not to lower the efficiency of the magnetic reconnections that maintain the plasma torus at the expense of the plasma centerpost. Boundary conditions have been corrected, up to the point that the first sustainment in steady state has been achieved for the combined plasma.","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":"139269058","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}
Streamer is an important stage in the initiation of gap discharge. In this work, we used an 8-frame intensified charge coupled device (ICCD) camera to capture the streamer development process when the lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod-plate gap, and the streamer velocity was analyzed. By analyzing the observations, the streamer velocity is defined as three stages: rapid velocity decline (stage 1), rapid velocity rise (stage 2) and slow velocity decline (stage 3). The effects of electrode shape, applied voltage, gap breakdown or withstand on streamer velocity were analyzed. The electrode with a larger curvature radius will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with the previous results and the statistical characteristics of the primary streamer discharge were discussed.
{"title":"Dynamic propagation velocity of positive streamer in a 3 m air gap under lightning impulse voltage","authors":"Zhiwei Li, Ting Lei, Yu Su, Xiuyuan Yao, Bingxue Yang, Delong Liu, Fangcheng Lv, Yujian Ding","doi":"10.1088/2058-6272/ad0d51","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d51","url":null,"abstract":"Streamer is an important stage in the initiation of gap discharge. In this work, we used an 8-frame intensified charge coupled device (ICCD) camera to capture the streamer development process when the lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod-plate gap, and the streamer velocity was analyzed. By analyzing the observations, the streamer velocity is defined as three stages: rapid velocity decline (stage 1), rapid velocity rise (stage 2) and slow velocity decline (stage 3). The effects of electrode shape, applied voltage, gap breakdown or withstand on streamer velocity were analyzed. The electrode with a larger curvature radius will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with the previous results and the statistical characteristics of the primary streamer discharge were discussed.","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":"139269997","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}
Reconstruction of plasma equilibrium plays an important role in the analysis and simulation of plasma experiments. The kinetic equilibrium reconstruction with pressure and edge current constraints has been employed on EAST tokamak. However, the internal safety factor (q) profile is not accurate. This paper proposes a new way of incorporating q profile constraints into kinetic equilibrium reconstruction. The q profile is yielded from the Polarimeter Interferometer (POINT) reconstruction. Virtual probes containing information on q profile constraints are added to inputs of the kinetic equilibrium reconstruction program to obtain the final equilibrium. The new equilibrium produces a more accurate internal q profile. This improved method would help analyze EAST experiments.
等离子体平衡重构在等离子体实验的分析和模拟中发挥着重要作用。EAST 托卡马克已经采用了具有压力和边缘电流约束的动力学平衡重建。然而，内部安全系数（q）曲线并不准确。本文提出了一种将 q 曲线约束纳入动力学平衡重构的新方法。q剖面由偏振干涉仪（POINT）重建得出。将包含q剖面约束信息的虚拟探测器添加到动力学平衡重建程序的输入中，以获得最终平衡。新的平衡产生了更精确的内部 q 曲线。这种改进的方法将有助于分析 EAST 实验。
{"title":"Kinetic equilibrium reconstruction with internal safety factor profile constraints on EAST tokamak","authors":"Haochen Fan, Guoqiang Li, Jinping Qian, Xuexi Zhang, Xiaohe Wu, Yuqi Chu, Xiang Zhu, Hui Lian, Haiqing Liu, Bo Lyu, Yifei Jin, Qing Zang, Jia Huang","doi":"10.1088/2058-6272/ad0d48","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d48","url":null,"abstract":"Reconstruction of plasma equilibrium plays an important role in the analysis and simulation of plasma experiments. The kinetic equilibrium reconstruction with pressure and edge current constraints has been employed on EAST tokamak. However, the internal safety factor (q) profile is not accurate. This paper proposes a new way of incorporating q profile constraints into kinetic equilibrium reconstruction. The q profile is yielded from the Polarimeter Interferometer (POINT) reconstruction. Virtual probes containing information on q profile constraints are added to inputs of the kinetic equilibrium reconstruction program to obtain the final equilibrium. The new equilibrium produces a more accurate internal q profile. This improved method would help analyze EAST experiments.","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":"139267676","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/ad0d5a
Lei Wang, Can Huang, Dongke Chen, Zhongwei Yang, A. Du, Y. Ge
We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary (PB) and fully-opened boundary (OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.
我们进行了二维粒子入胞模拟，以研究边界条件对磁重联演化的影响。结果表明，边界条件对这种演化至关重要。具体来说，在传统周期性边界条件（PB）和完全开放边界条件（OB）的情况下，系统在达到最快再连接速率之前的演化非常相似。然而，之后两种情况就出现了差异。在 PB 条件下，重连接电场迅速下降，甚至变为负值，表明重连接过程发生了逆转。相反，在 OB 情况下，系统保持着快速重连接阶段。两种模拟情况的分离矩阵附近和排气区都产生了过热电子。在电子密度耗尽层和双极化前沿区域，OB 情况下产生的超热电子比例更大。在两种情况下，中能电子主要位于 X 线附近和再连接点下游。不过，在转子情况下，中能电子也可能在沿分离矩阵的电子空穴中产生。在反向重联阶段之前，PB 情况下不存在高能电子。相反，在 OB 情况下，细长电子流层中约有 20% 的电子是高能电子。
{"title":"The influence of boundary conditions on the distribution of energetic electrons during collisionless magnetic reconnection","authors":"Lei Wang, Can Huang, Dongke Chen, Zhongwei Yang, A. Du, Y. Ge","doi":"10.1088/2058-6272/ad0d5a","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d5a","url":null,"abstract":"We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary (PB) and fully-opened boundary (OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.","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":"139268908","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/ad0d4e
Ming Chen, Biao Shen, S. Kado, B. Guo, Dalong Chen, Furui Cai, Bing-biao Xiao
To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future Tokamak, a Dα band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak. This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%. The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the Tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT results. This underscores the system’s superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.
{"title":"Development of Dα band symmetrical visible optical diagnostic for boundary reconstruction on EAST tokamak","authors":"Ming Chen, Biao Shen, S. Kado, B. Guo, Dalong Chen, Furui Cai, Bing-biao Xiao","doi":"10.1088/2058-6272/ad0d4e","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d4e","url":null,"abstract":"To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future Tokamak, a Dα band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak. This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%. The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the Tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT results. This underscores the system’s superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.","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":"139266946","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/ad0d55
Xingkang Wang, W. Mao, Jinlin Xie, T. Lan, Hong Li, A. Liu, Chu Zhou, X. Wen, Zian Wei, Jie Wu, Chen Chen, Dongkuan Liu, Xianhao Rao, Hu Cai, Jiaren Wu, Peng Deng, Haiqing Liu, Weixing Ding, Zhuang Ge, Wandong Liu
A multi-channel polarimeter-interferometer has been developed on the Keda Torus eXperiment (KTX) for the study of equilibrium dynamics and internal magnetic fluctuations. Three-wave technique based on terahertz solid state sources (~650 GHz) is applied for simultaneous measurements of electron density and Faraday rotation angle. The output power of the microwave source is 2 mW. Faraday rotation effect using a rotating wave plate is tested with phase noise less than 0.8°, and the density phase noise is less than 0.9°. Measurement of Faraday rotation angle and density for discharges on KTX have demonstrated high sensitivity to internal MHD activities.
{"title":"Polarimeter-interferometer diagnostic using terahertz solid state sources for fluctuation measurements on Keda Torus eXperiment (KTX)","authors":"Xingkang Wang, W. Mao, Jinlin Xie, T. Lan, Hong Li, A. Liu, Chu Zhou, X. Wen, Zian Wei, Jie Wu, Chen Chen, Dongkuan Liu, Xianhao Rao, Hu Cai, Jiaren Wu, Peng Deng, Haiqing Liu, Weixing Ding, Zhuang Ge, Wandong Liu","doi":"10.1088/2058-6272/ad0d55","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d55","url":null,"abstract":"A multi-channel polarimeter-interferometer has been developed on the Keda Torus eXperiment (KTX) for the study of equilibrium dynamics and internal magnetic fluctuations. Three-wave technique based on terahertz solid state sources (~650 GHz) is applied for simultaneous measurements of electron density and Faraday rotation angle. The output power of the microwave source is 2 mW. Faraday rotation effect using a rotating wave plate is tested with phase noise less than 0.8°, and the density phase noise is less than 0.9°. Measurement of Faraday rotation angle and density for discharges on KTX have demonstrated high sensitivity to internal MHD activities.","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":"139269985","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}
In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of PI composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.
与传统变压器相比，电力电子变压器作为新能源电力系统中不可或缺的组成部分，经常会受到高频和瞬态电应力的影响，导致绝缘失效问题备受关注。与此同时，高频电应力下放电击穿失效和纳米填料增强的内在机理仍不清楚。本文构建了一个电热耦合放电击穿相场模型，以研究聚酰亚胺纳米复合绝缘材料在高频应力作用下的击穿路径演变。研究重点是分析频率、温度和纳米填料形状等各种因素对 PI 复合材料击穿路径的影响。此外，研究还阐明了纳米改性复合绝缘材料在中观尺度上的增强机制。结果表明，随着频率和温度的升高，放电击穿路径呈现加速发展，焦耳热能逐渐占据主导地位。这种增强归因于分散的电场分布和纳米片的阻碍效应。研究结果为高频电力设备中使用的新型绝缘材料的优化设计和性能管理提供了理论基础和方法框架。
{"title":"Phase field model for electric-thermal coupled discharge breakdown of polyimide nanocomposites under high frequency electrical stress","authors":"Zhiyun Han, Qingmin Li, Junke Li, Mengxi Wang, Hanwen Ren, Liang Zou","doi":"10.1088/2058-6272/ad0d49","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d49","url":null,"abstract":"In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of PI composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.","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":"139266831","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/ad0d5b
Yiming Sun, Hanwen Deng, Xinyu Liu, Xiaoming Kang
Field emission electric propulsion (FEEP) thrusters possess excellent characteristics such as high specific impulse, low power requirements, compact size, and precise pointing capabilities, making them ideal propulsion devices for micro-nano satellites. However, the detection of certain aspects, such as the evolution process of the liquid cone and the physical quantities at the cone apex, proves challenging due to the minute size of the needle tip and the vacuum environment in which they operate. Consequently, this paper introduces a computational fluid dynamics (CFD) model to gain insights into the formation process of the liquid cone on the tip apex of Indium FEEP. The CFD model is based on the electrohydrodynamic (EHD) equations and the volume of fluid (VOF) method. The entire cone formation process can be divided into three stages, and the time-dependent characteristics of the physical quantities at the cone apex are investigated. The influences of film thickness, apex radius size, and applied voltage are compared. The results indicate a gradual increase in the values of electrostatic stress and surface tension stress at the cone apex over an initial period, followed by a rapid escalation within a short duration. Apex configurations featuring a small radius, thick film, and high voltage exhibit a propensity for liquid cone formation, and the cone growth time decreasing as the film thickness increases. Moreover, some unstable behavior is observed during the cone formation process.
{"title":"Simulation of liquid cone formation on the tip apex of indium field emission electric propulsion thrusters","authors":"Yiming Sun, Hanwen Deng, Xinyu Liu, Xiaoming Kang","doi":"10.1088/2058-6272/ad0d5b","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d5b","url":null,"abstract":"Field emission electric propulsion (FEEP) thrusters possess excellent characteristics such as high specific impulse, low power requirements, compact size, and precise pointing capabilities, making them ideal propulsion devices for micro-nano satellites. However, the detection of certain aspects, such as the evolution process of the liquid cone and the physical quantities at the cone apex, proves challenging due to the minute size of the needle tip and the vacuum environment in which they operate. Consequently, this paper introduces a computational fluid dynamics (CFD) model to gain insights into the formation process of the liquid cone on the tip apex of Indium FEEP. The CFD model is based on the electrohydrodynamic (EHD) equations and the volume of fluid (VOF) method. The entire cone formation process can be divided into three stages, and the time-dependent characteristics of the physical quantities at the cone apex are investigated. The influences of film thickness, apex radius size, and applied voltage are compared. The results indicate a gradual increase in the values of electrostatic stress and surface tension stress at the cone apex over an initial period, followed by a rapid escalation within a short duration. Apex configurations featuring a small radius, thick film, and high voltage exhibit a propensity for liquid cone formation, and the cone growth time decreasing as the film thickness increases. Moreover, some unstable behavior is observed during the cone formation process.","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":"139268444","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/ad0d50
Yalong Li, Kun Wan, Yufei Wang, Xiaoxing Zhang, Zhaodi Yang, Mingli Fu, R. Zhuo, Dibo Wang
SF6 has excellent insulation performance and arc extinguishing ability, and is widely used in the power industry. However, its global warming potential is about 23500 times that of CO2, and it can exist stably in the atmospheric environment, is not easy to degrade, and has great potential harm to the environment. Based on pulsed dielectric barrier discharge plasma technology, the effects of H2O and O2 on the degradation of SF6 were studied. Studies have shown that H2O and O2 can effectively promote the decomposition of SF6 and improve its degradation rate and energy efficiency. Under the action of pulse input voltage and an input frequency of 15 kV and 15 kHz respectively, when H2O has added alone, the effect of 1 % H2O is the best, and the degradation rate and energy efficiency of SF6 reach the maximum, which is 91.9 % and 8.25 g/kWh, respectively. The synergistic effect of H2O and O2 on the degradation of SF6 was similar to that of H2O. When the concentration of H2O and O2 was 1 %, the system obtained the best degradation rate and energy efficiency, which were 89.7 % and 8.05 g / kWh, respectively. At the same time, different external gases exhibit different decomposition product regulation capabilities. The addition of H2O can effectively improve the selectivity of SO2. Under the synergistic effect of H2O and O2, with the increase of O2 concentration, the degradation products gradually transformed into SO2F2.
{"title":"Experimental study on the effect of H2O and O2 on the degradation of SF6 by pulsed dielectric barrier discharge","authors":"Yalong Li, Kun Wan, Yufei Wang, Xiaoxing Zhang, Zhaodi Yang, Mingli Fu, R. Zhuo, Dibo Wang","doi":"10.1088/2058-6272/ad0d50","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d50","url":null,"abstract":"SF6 has excellent insulation performance and arc extinguishing ability, and is widely used in the power industry. However, its global warming potential is about 23500 times that of CO2, and it can exist stably in the atmospheric environment, is not easy to degrade, and has great potential harm to the environment. Based on pulsed dielectric barrier discharge plasma technology, the effects of H2O and O2 on the degradation of SF6 were studied. Studies have shown that H2O and O2 can effectively promote the decomposition of SF6 and improve its degradation rate and energy efficiency. Under the action of pulse input voltage and an input frequency of 15 kV and 15 kHz respectively, when H2O has added alone, the effect of 1 % H2O is the best, and the degradation rate and energy efficiency of SF6 reach the maximum, which is 91.9 % and 8.25 g/kWh, respectively. The synergistic effect of H2O and O2 on the degradation of SF6 was similar to that of H2O. When the concentration of H2O and O2 was 1 %, the system obtained the best degradation rate and energy efficiency, which were 89.7 % and 8.05 g / kWh, respectively. At the same time, different external gases exhibit different decomposition product regulation capabilities. The addition of H2O can effectively improve the selectivity of SO2. Under the synergistic effect of H2O and O2, with the increase of O2 concentration, the degradation products gradually transformed into SO2F2.","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":"139268772","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/ad0d4b
R. He, T. Xu, Xiaoyi Yang, Chijie Xiao, Zuyu Zhang, Ruixin Yuan, Xiaogang Wang, Zhibin Guo, Xiuming Yu, Yue Ge
The acceleration of electrons near three-dimensional (3D) magnetic nulls is crucially to the energy conversion mechanism in the 3D magnetic reconnection process. To explore electron acceleration in a 3D magnetic null topology, we constructed a pair of 3D magnetic nulls in Peking university Plasma Test device (PPT) and observed acceleration of electrons near magnetic nulls. This study measured the plasma floating potential and ion density profiles ambient the 3D magnetic null. The potential wells near nulls may related to the energy variations of electrons, so we measured the electron distribution functions (EDF) at different spatial positions. The axial variation of EDF shows that the electrons are deviated from the Maxwell distribution near magnetic nulls. With scanning probes that could measure directionally and theoretical analysis based on curves fitting, the variation of EDF are linked to the changes of plasma potential under 3D magnetic nulls’ topology. The kinetic energy of electrons accelerated by the electric field is 6eV (v_e~7v_(e-Alfven)) and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.
{"title":"Laboratory observation of electron energy distribution near three-dimensional magnetic nulls","authors":"R. He, T. Xu, Xiaoyi Yang, Chijie Xiao, Zuyu Zhang, Ruixin Yuan, Xiaogang Wang, Zhibin Guo, Xiuming Yu, Yue Ge","doi":"10.1088/2058-6272/ad0d4b","DOIUrl":"https://doi.org/10.1088/2058-6272/ad0d4b","url":null,"abstract":"The acceleration of electrons near three-dimensional (3D) magnetic nulls is crucially to the energy conversion mechanism in the 3D magnetic reconnection process. To explore electron acceleration in a 3D magnetic null topology, we constructed a pair of 3D magnetic nulls in Peking university Plasma Test device (PPT) and observed acceleration of electrons near magnetic nulls. This study measured the plasma floating potential and ion density profiles ambient the 3D magnetic null. The potential wells near nulls may related to the energy variations of electrons, so we measured the electron distribution functions (EDF) at different spatial positions. The axial variation of EDF shows that the electrons are deviated from the Maxwell distribution near magnetic nulls. With scanning probes that could measure directionally and theoretical analysis based on curves fitting, the variation of EDF are linked to the changes of plasma potential under 3D magnetic nulls’ topology. The kinetic energy of electrons accelerated by the electric field is 6eV (v_e~7v_(e-Alfven)) and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.","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":"139266619","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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