Using the SPIDER code, three series of calculations of plasma equilibrium in a tokamak are performed—with low, medium, and high pressure. In each series, the cross section is purely elliptical with elongation varying from K=1 (circular plasma) to K=2.4. For these configurations, the integrals S1÷S3 defining the right-hand sides of the virial relations in Lao et al. [Nucl. Fusion 25, 1421 (1985)] are calculated. Their dependences on plasma parameters, elongation K of magnetic surfaces, and radial derivatives of K and Shafranov shift Δ are analyzed. The accuracy of analytical expressions for S1÷S3 proposed in Pustovitov [Phys. Plasmas 29, 092507 (2022)] is assessed.
{"title":"Virial relations for elongated plasmas in tokamaks: Analytical approximations and numerical calculations","authors":"A. A. Martynov, V. D. Pustovitov","doi":"10.1063/5.0221175","DOIUrl":"https://doi.org/10.1063/5.0221175","url":null,"abstract":"Using the SPIDER code, three series of calculations of plasma equilibrium in a tokamak are performed—with low, medium, and high pressure. In each series, the cross section is purely elliptical with elongation varying from K=1 (circular plasma) to K=2.4. For these configurations, the integrals S1÷S3 defining the right-hand sides of the virial relations in Lao et al. [Nucl. Fusion 25, 1421 (1985)] are calculated. Their dependences on plasma parameters, elongation K of magnetic surfaces, and radial derivatives of K and Shafranov shift Δ are analyzed. The accuracy of analytical expressions for S1÷S3 proposed in Pustovitov [Phys. Plasmas 29, 092507 (2022)] is assessed.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"37 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883804","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}
R. D. Sydora, T. Simala-Grant, S. Karbashewski, F. Jimenez, B. Van Compernolle, M. J. Poulos
A set of experiments using controlled, skin depth-sized plasma pressure filaments in close proximity have been carried out in a large linear magnetized plasma device. Two- and three-filament configurations have been used to determine the scale of cross field nonlinear interaction. When the filaments are separated by a distance of approximately five times the size of a single filament or less, a significant transfer of charge and energy occurs, leading to the generation of inter-filament electric fields. This has the effect of rotating the filaments and influencing the merging dynamics. Nonlinear gyrokinetic simulations using seeded filaments confirm the presence of unstable drift-Alfvén modes driven by the steep electron temperature gradient. When the filaments are within a few collisionless electron skin depths (separations twice the size of a single filament), the unstable perturbations drive the convective mixing of the density and temperature and rearrange the gradients such that they maximize in the region surrounding the filament bundle.
{"title":"Experiments and gyrokinetic simulations of the nonlinear interaction between spinning magnetized plasma pressure filaments","authors":"R. D. Sydora, T. Simala-Grant, S. Karbashewski, F. Jimenez, B. Van Compernolle, M. J. Poulos","doi":"10.1063/5.0213345","DOIUrl":"https://doi.org/10.1063/5.0213345","url":null,"abstract":"A set of experiments using controlled, skin depth-sized plasma pressure filaments in close proximity have been carried out in a large linear magnetized plasma device. Two- and three-filament configurations have been used to determine the scale of cross field nonlinear interaction. When the filaments are separated by a distance of approximately five times the size of a single filament or less, a significant transfer of charge and energy occurs, leading to the generation of inter-filament electric fields. This has the effect of rotating the filaments and influencing the merging dynamics. Nonlinear gyrokinetic simulations using seeded filaments confirm the presence of unstable drift-Alfvén modes driven by the steep electron temperature gradient. When the filaments are within a few collisionless electron skin depths (separations twice the size of a single filament), the unstable perturbations drive the convective mixing of the density and temperature and rearrange the gradients such that they maximize in the region surrounding the filament bundle.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"75 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883805","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}
Zhang-Hu Hu, Wen-Yuan Zhai, Jie-Jie Lan, You-Nian Wang
We investigate in this work the photon radiation of relativistic electron beams in the magnetic fields induced by plasma current filamentation instability. An analytical model is proposed, and the radiated power is shown to depend only on the beam density, charge, and energy. The radiated power in the beam–plasma system increases significantly in the linear stage of the instability due to beam filament merger and becomes saturated in the nonlinear stage. Detailed electromagnetic particle-in-cell simulations are performed and the nonlinear scalings of the radiated power with beam parameters are found, showing good agreement with the analytical model.
{"title":"Nonlinear scaling of photon radiation power in relativistic plasma current filamentation instability with beam parameters","authors":"Zhang-Hu Hu, Wen-Yuan Zhai, Jie-Jie Lan, You-Nian Wang","doi":"10.1063/5.0210348","DOIUrl":"https://doi.org/10.1063/5.0210348","url":null,"abstract":"We investigate in this work the photon radiation of relativistic electron beams in the magnetic fields induced by plasma current filamentation instability. An analytical model is proposed, and the radiated power is shown to depend only on the beam density, charge, and energy. The radiated power in the beam–plasma system increases significantly in the linear stage of the instability due to beam filament merger and becomes saturated in the nonlinear stage. Detailed electromagnetic particle-in-cell simulations are performed and the nonlinear scalings of the radiated power with beam parameters are found, showing good agreement with the analytical model.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"54 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883808","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}
M. Mounho, C. Fuksa, R. Clark, W. Brooks, M. Hopkins, A. Steiner, A. Neuber, J. Stephens
This manuscript reports the experimental study of a novel vacuum high-voltage (HV) feedthrough geometry with a recessed anode triple junction (ATJ) relevant to large-scale pulsed power systems. It is shown experimentally that introducing a vacuum gap between the insulator–anode interface and recessing the ATJ farther away from the cathode triple junction significantly enhances high voltage (HV) vacuum surface flashover hold-off. The results for “first pulse” and “consecutive pulse” tests are reported. The physical mechanisms contributing to the electrical failure of this feedthrough geometry appear to be unique to this geometry. These findings show the potential to allow for HV vacuum surface flashover geometries with significantly improved electrical characteristics.
{"title":"Statistical characterization of high voltage vacuum surface flashover with gapped and ungapped anodes","authors":"M. Mounho, C. Fuksa, R. Clark, W. Brooks, M. Hopkins, A. Steiner, A. Neuber, J. Stephens","doi":"10.1063/5.0214059","DOIUrl":"https://doi.org/10.1063/5.0214059","url":null,"abstract":"This manuscript reports the experimental study of a novel vacuum high-voltage (HV) feedthrough geometry with a recessed anode triple junction (ATJ) relevant to large-scale pulsed power systems. It is shown experimentally that introducing a vacuum gap between the insulator–anode interface and recessing the ATJ farther away from the cathode triple junction significantly enhances high voltage (HV) vacuum surface flashover hold-off. The results for “first pulse” and “consecutive pulse” tests are reported. The physical mechanisms contributing to the electrical failure of this feedthrough geometry appear to be unique to this geometry. These findings show the potential to allow for HV vacuum surface flashover geometries with significantly improved electrical characteristics.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"47 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883862","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}
Vipin K. Yadav, Mahima Agarwal, Mehul Chakraborty, Rajneesh Kumar
The analytical study of the two-stream instability (TSI) generation is carried out in the lunar ionosphere. The solar wind is considered an electron beam, which interacts with the lunar ionosphere, generated due to the photoionization of the lunar neutrals by the extreme ultraviolet component of the solar radiation. In this interaction process, the lunar electrons constitute the background plasma as the ion population is considerably low in the lunar plasma environment. In the present study along with the non-energetic (“cold”) electrons, which are in the majority, a fraction of energetic electrons (“hot”) of the total lunar electron population are also considered and the fraction of energetic electrons is taken in the range of 1%–25% of the total lunar electron count. The particle-in-cell simulations suggest that the presence of energetic electrons in the lunar plasma environment hastens the electron bunching during the interaction with the incoming solar wind electrons during the TSI. The energetic electrons in the lunar plasma environment are capable of triggering non-linear phenomena, such as the generation of lunar plasma waves. The inclusion of hot electrons in the lunar plasma ambiance changes the scenario for the TSI to occur in the lunar ionosphere, and the analysis shows that it modifies the TSI dispersion relation and can have a significant impact on the growth and decay of the TSI and its threshold for generation in a lunar plasma environment.
在月球电离层对双流不稳定性（TSI）的产生进行了分析研究。太阳风被认为是一种电子束，它与月球电离层相互作用，是由于月球中性物质在太阳辐射的极紫外分量作用下发生光离子化而产生的。在这一相互作用过程中，月球电子构成了背景等离子体，因为月球等离子体环境中的离子群相当低。在本研究中，除了占大多数的非能量电子（"冷 "电子）外，还考虑了月球电子总数中的一部分高能电子（"热 "电子），高能电子占月球电子总数的 1%-25%。粒子入室模拟表明，月球等离子体环境中高能电子的存在加速了在TSI期间与进入的太阳风电子相互作用时的电子束化。月球等离子体环境中的高能电子能够引发非线性现象，如产生月球等离子体波。月球等离子体环境中热电子的加入改变了月球电离层中发生 TSI 的情景，分析表明它改变了 TSI 的弥散关系，并可能对 TSI 的增长和衰减及其在月球等离子体环境中产生的阈值产生重大影响。
{"title":"The effect of energetic electrons in lunar ionosphere on the streaming plasma instability around moon","authors":"Vipin K. Yadav, Mahima Agarwal, Mehul Chakraborty, Rajneesh Kumar","doi":"10.1063/5.0201367","DOIUrl":"https://doi.org/10.1063/5.0201367","url":null,"abstract":"The analytical study of the two-stream instability (TSI) generation is carried out in the lunar ionosphere. The solar wind is considered an electron beam, which interacts with the lunar ionosphere, generated due to the photoionization of the lunar neutrals by the extreme ultraviolet component of the solar radiation. In this interaction process, the lunar electrons constitute the background plasma as the ion population is considerably low in the lunar plasma environment. In the present study along with the non-energetic (“cold”) electrons, which are in the majority, a fraction of energetic electrons (“hot”) of the total lunar electron population are also considered and the fraction of energetic electrons is taken in the range of 1%–25% of the total lunar electron count. The particle-in-cell simulations suggest that the presence of energetic electrons in the lunar plasma environment hastens the electron bunching during the interaction with the incoming solar wind electrons during the TSI. The energetic electrons in the lunar plasma environment are capable of triggering non-linear phenomena, such as the generation of lunar plasma waves. The inclusion of hot electrons in the lunar plasma ambiance changes the scenario for the TSI to occur in the lunar ionosphere, and the analysis shows that it modifies the TSI dispersion relation and can have a significant impact on the growth and decay of the TSI and its threshold for generation in a lunar plasma environment.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"80 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883809","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}
Low magnetic field density peak (LFP) is a typical nonlinear phenomenon in helicon wave discharge, which is characterized by the nonlinear increase in electron density with the magnetic field in lower magnetic fields. In this paper, the characteristics and generation mechanism of LFPs of argon helicon wave plasma excited by m = 0 single-loop antenna are studied by experiment and numerical simulation. Experimental results show that plasma density shows two peaks at increasing magnetic field in the range of 0–100 G. The first peak appears around 10 G, and the second one appears between 30 and 50 G. The peak density is related to gas pressure, radio frequency power, and tube dimension. From B-dot measurement, there exists obvious helicon wave structure in plasma at field strength around the LFP, with component of standing wave. Theoretical analysis demonstrated that the first density peak occurs on the demarcation line in density-magnetic field map where the H-wave limited by radial boundary condition begins to propagate, while the second peak is due to the fact that the axial wavenumber of H-wave decreases gradually with the increased magnetic field and the heating effect by standing wave resonance coupling is weakened above a critical magnetic field, leading to a sudden decrease in plasma density. Simulation by HELIC code shows that the change of radial distribution of power deposition reflects the conversion of heating mechanism from single TG-wave mode to H-TG wave coupled mode heating in low magnetic fields. The axial wavenumber with the maximum absorbed power decreases with the increased magnetic field, corresponding to the change of wave structure.
低磁场密度峰（LFP）是氦波放电中一种典型的非线性现象，其特点是在低磁场中电子密度随磁场的变化而非线性增加。本文通过实验和数值模拟研究了由 m = 0 单环天线激发的氩氦波等离子体的 LFP 特性和产生机理。实验结果表明，在 0-100 G 的磁场范围内，等离子体密度在磁场增大时会出现两个峰值，第一个峰值出现在 10 G 左右，第二个峰值出现在 30-50 G 之间。从 B 点测量结果来看，在 LFP 附近的场强下，等离子体中存在明显的螺旋波结构，并有驻波成分。理论分析表明，第一个密度峰出现在密度-磁场图的分界线上，受径向边界条件限制的 H 波在该处开始传播，而第二个密度峰则是由于 H 波的轴向波数随磁场增大而逐渐减小，驻波共振耦合的加热效应在临界磁场之上减弱，从而导致等离子体密度骤减。HELIC 代码的模拟表明，功率沉积径向分布的变化反映了低磁场下加热机制从单一 TG 波模式向 H-TG 波耦合模式加热的转换。吸收功率最大的轴向波数随着磁场的增大而减小，这与波的结构变化相对应。
{"title":"Characteristics and mechanism of low-field peak in argon helicon plasma of single loop antenna","authors":"Zhangyu Xia, Tianliang Zhang, Ying Cui, Bocong Zheng, Jiting Ouyang","doi":"10.1063/5.0213521","DOIUrl":"https://doi.org/10.1063/5.0213521","url":null,"abstract":"Low magnetic field density peak (LFP) is a typical nonlinear phenomenon in helicon wave discharge, which is characterized by the nonlinear increase in electron density with the magnetic field in lower magnetic fields. In this paper, the characteristics and generation mechanism of LFPs of argon helicon wave plasma excited by m = 0 single-loop antenna are studied by experiment and numerical simulation. Experimental results show that plasma density shows two peaks at increasing magnetic field in the range of 0–100 G. The first peak appears around 10 G, and the second one appears between 30 and 50 G. The peak density is related to gas pressure, radio frequency power, and tube dimension. From B-dot measurement, there exists obvious helicon wave structure in plasma at field strength around the LFP, with component of standing wave. Theoretical analysis demonstrated that the first density peak occurs on the demarcation line in density-magnetic field map where the H-wave limited by radial boundary condition begins to propagate, while the second peak is due to the fact that the axial wavenumber of H-wave decreases gradually with the increased magnetic field and the heating effect by standing wave resonance coupling is weakened above a critical magnetic field, leading to a sudden decrease in plasma density. Simulation by HELIC code shows that the change of radial distribution of power deposition reflects the conversion of heating mechanism from single TG-wave mode to H-TG wave coupled mode heating in low magnetic fields. The axial wavenumber with the maximum absorbed power decreases with the increased magnetic field, corresponding to the change of wave structure.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"217 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883810","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 phenomenon of laser-driven heating wave propagation in a plasma with a density less than the critical density is considered for the case of a finite radius of the laser beam. Based on computational and theoretical studies, the effect of channeling the heating wave propagation in the central axial region of plasma due to the reflection of laser radiation on density gradient, formed by plasma motion, at the tuning point was found. Unlike the self-focusing phenomenon, where the laser flux is concentrated without ray intersection, in refractive channeling, this occurs due to ray intersection. This is similar to the creation of a high flux density during multi-beam irradiation of the laser target. It is shown that the longitudinal velocity of heating wave in the channeling region is significantly larger compared with that in the peripheral plasma regions located at a distance of about laser beam radius.
{"title":"Refractive channeling of heating wave driven by laser beam interaction with plasma of subcritical density","authors":"S. Yu. Gus'kov, P. A. Kuchugov, N. N. Demchenko","doi":"10.1063/5.0194806","DOIUrl":"https://doi.org/10.1063/5.0194806","url":null,"abstract":"The phenomenon of laser-driven heating wave propagation in a plasma with a density less than the critical density is considered for the case of a finite radius of the laser beam. Based on computational and theoretical studies, the effect of channeling the heating wave propagation in the central axial region of plasma due to the reflection of laser radiation on density gradient, formed by plasma motion, at the tuning point was found. Unlike the self-focusing phenomenon, where the laser flux is concentrated without ray intersection, in refractive channeling, this occurs due to ray intersection. This is similar to the creation of a high flux density during multi-beam irradiation of the laser target. It is shown that the longitudinal velocity of heating wave in the channeling region is significantly larger compared with that in the peripheral plasma regions located at a distance of about laser beam radius.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"57 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883899","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}
Interactions of floating potential on metal and dielectric targets with He atmospheric pressure plasma jet (APPJ) were studied in this paper. The APPJ is generated in a needle-ring corona-dielectric barrier discharge configuration, driven by a sinusoidal voltage. The characteristics of APPJ were assessed through electrical and optical examinations, and the time-average electrostatic voltage on the targets was measured using both contact and non-contact electrostatic voltmeters. It was found that both metal and dielectric targets can promote the jet development and speed up the jet velocity. During the negative half-cycle, the “plasma cluster” propagates from the target toward the ground electrode and then “merges” with the forward plasma jet, leading to a reversed development of jet. The two targets follow a similar pattern on the surface electrostatic voltage, that is, initially in a positive polarity whose amplitude first increases and then decreases and transits to negative polarity with an increase in the applied voltage. But there are also some minor differences between the two targets, e.g., the metallic target can change the discharge pattern and reduces the discharge current under certain conditions.
{"title":"Interaction between atmospheric pressure plasma jet and target","authors":"Gaosheng He, Yuqing Liu, Feng He, Jinsong Miao, Jingran Li, Yu Zhang, Zhiliang Gao, Ruojue Wang, Xu Yan, Jiting Ouyang","doi":"10.1063/5.0205130","DOIUrl":"https://doi.org/10.1063/5.0205130","url":null,"abstract":"Interactions of floating potential on metal and dielectric targets with He atmospheric pressure plasma jet (APPJ) were studied in this paper. The APPJ is generated in a needle-ring corona-dielectric barrier discharge configuration, driven by a sinusoidal voltage. The characteristics of APPJ were assessed through electrical and optical examinations, and the time-average electrostatic voltage on the targets was measured using both contact and non-contact electrostatic voltmeters. It was found that both metal and dielectric targets can promote the jet development and speed up the jet velocity. During the negative half-cycle, the “plasma cluster” propagates from the target toward the ground electrode and then “merges” with the forward plasma jet, leading to a reversed development of jet. The two targets follow a similar pattern on the surface electrostatic voltage, that is, initially in a positive polarity whose amplitude first increases and then decreases and transits to negative polarity with an increase in the applied voltage. But there are also some minor differences between the two targets, e.g., the metallic target can change the discharge pattern and reduces the discharge current under certain conditions.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"159 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883863","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}
Xin Ai, Qiuyue Nie, Zhonglin Zhang, Shu Lin, Peiqi Chen, Changshi Yan, Chuanping Yu, Zhenghang Fei, Xingyu Zhao
Two kinds of fluorides are proposed innovatively to modulate the dielectric property of the plasma by reducing the electron density. There is a maximum of 74.41% electron density reduction after the fluorides are injected into the plasma at a magnitude of 1019 m−3, and the corresponding plasma frequency reduction is 49.42%. The fluorides proposed in this paper exhibit a wider modulation range, a faster modulation speed, and a longer maintenance time compared with SF6. The electromagnetic (EM) wave transmission characteristics in plasma are modulated correspondingly. The attenuation of S21 is reduced by 15.11–20.11 dB in 6–18 GHz, and an enhancement in the whole experimental frequency range is observed compared with SF6. The results of the paper can be applied in the mitigation of reentry vehicle's EM wave attenuation induced by the over-dense plasma sheath covering the vehicle. In addition, it also has a potential in broad applications of EM wave and plasma interactions.
{"title":"Electron density control by fluorides for dielectric property modulation in gaseous discharge plasmas","authors":"Xin Ai, Qiuyue Nie, Zhonglin Zhang, Shu Lin, Peiqi Chen, Changshi Yan, Chuanping Yu, Zhenghang Fei, Xingyu Zhao","doi":"10.1063/5.0215387","DOIUrl":"https://doi.org/10.1063/5.0215387","url":null,"abstract":"Two kinds of fluorides are proposed innovatively to modulate the dielectric property of the plasma by reducing the electron density. There is a maximum of 74.41% electron density reduction after the fluorides are injected into the plasma at a magnitude of 1019 m−3, and the corresponding plasma frequency reduction is 49.42%. The fluorides proposed in this paper exhibit a wider modulation range, a faster modulation speed, and a longer maintenance time compared with SF6. The electromagnetic (EM) wave transmission characteristics in plasma are modulated correspondingly. The attenuation of S21 is reduced by 15.11–20.11 dB in 6–18 GHz, and an enhancement in the whole experimental frequency range is observed compared with SF6. The results of the paper can be applied in the mitigation of reentry vehicle's EM wave attenuation induced by the over-dense plasma sheath covering the vehicle. In addition, it also has a potential in broad applications of EM wave and plasma interactions.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"34 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883870","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 the pressure range of 1–40 atm, experimental and theoretical studies of the processes of initiation and development dynamics of the initial stage of the self-sustained subnanosecond discharge in nitrogen, developing in a uniform electric field with the participation of runaway electrons, were carried out. Data on the maximum achievable values of the electric field strength in the discharge gap at the pre-breakdown stage of the discharge development and photographs of the microrelief of the surface of a stainless steel cathode formed during its training by subnanosecond high-voltage pulses were obtained. These data served as the basis for numerical 3D modeling of the development of an electron avalanche initiated by a field emission electron in a small region of enhanced electric field near a microinhomogeneity on the cathode. The possibility of transition of electrons in these avalanches to the runaway regime was studied. Cone-shaped microprotrusions, metal drops, and boundaries between pores and microcraters were considered as microinhomogeneities. It has been shown that the initial energy obtained by an electron near the microinhomogeneity can significantly facilitate its transfer into the runaway regime. This effect is especially noticeable at gas pressures higher 10 atm. As a result, at the stage of a self-sustained subnanosecond discharge formation, the runaway mode of an electron can be realized at the average reduced electric field strengths in the discharge gap, which are significantly lower than required by the runaway criterion.
{"title":"Investigation of the possibility of generation of runaway electrons in subnanosecond gas discharges of high and ultrahigh pressure in the vicinity of microprotrusions on the cathode surface","authors":"Stepan N. Ivanov, Vasily V. Lisenkov","doi":"10.1063/5.0217390","DOIUrl":"https://doi.org/10.1063/5.0217390","url":null,"abstract":"In the pressure range of 1–40 atm, experimental and theoretical studies of the processes of initiation and development dynamics of the initial stage of the self-sustained subnanosecond discharge in nitrogen, developing in a uniform electric field with the participation of runaway electrons, were carried out. Data on the maximum achievable values of the electric field strength in the discharge gap at the pre-breakdown stage of the discharge development and photographs of the microrelief of the surface of a stainless steel cathode formed during its training by subnanosecond high-voltage pulses were obtained. These data served as the basis for numerical 3D modeling of the development of an electron avalanche initiated by a field emission electron in a small region of enhanced electric field near a microinhomogeneity on the cathode. The possibility of transition of electrons in these avalanches to the runaway regime was studied. Cone-shaped microprotrusions, metal drops, and boundaries between pores and microcraters were considered as microinhomogeneities. It has been shown that the initial energy obtained by an electron near the microinhomogeneity can significantly facilitate its transfer into the runaway regime. This effect is especially noticeable at gas pressures higher 10 atm. As a result, at the stage of a self-sustained subnanosecond discharge formation, the runaway mode of an electron can be realized at the average reduced electric field strengths in the discharge gap, which are significantly lower than required by the runaway criterion.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"4 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883806","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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