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Numerical simulation of the initial plasma formation and current transfer in single-wire electrical explosion in vacuum

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Chinese Physics B 2017年第7期26卷 256-261页

作者：王坤史宗谦石元杰白骏吴坚贾申利邱爱慈 Province–Ministry Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability Hebei University of Technology State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong University

In this paper, a computational model is constructed to investigate the phenomenon of the initial plasma formation and current transfer in the single-wire electrical explosion in a vacuum. The process of the single-wire electrical explosion is divided into four stages. Stage Ⅰ： the wire is in solid state. Stage Ⅱ： the melting stage. Stage Ⅲ： the wire melts completely and the initial plasma forms. Stage IV： the core and corona expand separately. The thermodynamic calculation is applied before the wire melts completely in stages Ⅰ and Ⅱ. In stage Ⅲ, a one-dimensional magnetohydrodynamics model comes into play until the instant when the voltage collapse occurs. The temperature, density, and velocity, which are derived from the magnetohydrodynamics calculation, are averaged over the distribution area. The averaged parameters are taken as the initial conditions for stage Ⅳ in which a simplified magnetohydrodynamics model is applied. A wide-range semi-empirical equation of state, which is established based on the Thomas-Fermi-Kirzhnits model, is constructed to describe the phase transition from solid state to plasma state. The initial plasma formation and the phenomenon of current transfer in the electrical explosion of aluminum wire are investigated using the computational model. Experiments of electrical explosion of aluminum wires are carried out to verify this model. Simulation results are also compared with experimental results of the electrical explosion of copper wire.

关键词： single-wire electrical explosion plasma formation current transfer

Optical diffraction gratings embedded in BK-7 glass by low-density plasma formation using femtosecond laser

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 165-169页

作者： Jung-Kyu PARK Sung-Hak CHO Kwang-Ho KIM Myung-Chang KANG Nano Machining Laboratory Korea Institute of Machinery and Material Daejeon 305-343 Korea National Core Research Center for Hybrid Materials Solution Pusan National University

The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti： sapphire laser （λp=790 rim）. The refractive index modifications with diameters ranging from 400 nm to 4 gm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1 ×10^13 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change （An） was estimated to be 1.5x10 2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.

关键词： BK-7 glass plate diffraction grating refractive index modification plasma formation femtosecond laser

Effect of microwave frequency on plasma formation in air breakdown at atmospheric pressure

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Chinese Physics B 2015年第10期24卷 336-339页

作者：赵朋程郭立新李慧敏 School of Physics and Optoelectronic Engineering Xidian University

Microwave breakdown at atmospheric pressure causes the formation of a discrete plasma structure. The onedimensional fluid model coupling Maxwell equations with plasma fluid equations is used to study the effect of the microwave frequency on the formation of air plasma. Simulation results show that, the filamentary plasma array propagating toward the microwave source is formed at different microwave frequencies. As the microwave frequency decreases, the ratio of the distance between two adjacent plasma filaments to the corresponding wavelength remains almost unchanged（on the order of 1/4）, while the plasma front propagates more slowly due to the increase in the formation time of the new plasma filament.

关键词： microwave frequency plasma formation air breakdown electron fluid model

In situ mitigation strategies for field emission-induced cavity faults using low-level radiofrequency system

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Nuclear Science and Techniques 2022年第11期33卷 46-60页

作者： Feng Qiu Yuan He An-Dong Wu Zhen-Long Zhu Guo-Dong Jiang Tian-Cai Jiang Zheng Gao Qi Chen Zong-Heng Xue Jin-Ying Ma Cheng-Ye Xu Zi-Qin Yang Gui-Rong Huang Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

In the Chinese ADS front-end demo superconducting radiofrequency linac(CAFe)at the Institute of Modern Physics,a burst-noise signal-triggered cavity fault frequently appears during beam *** events are characterized by a rapid burst noise in the cavity pick-up,which may lead to an unexpected low-level radiofrequency(LLRF)response that eventually causes a cavity *** eliminate the undesirable reaction of the LLRF control loop,we propose a method that uses a burstnoise detection and processing algorithm integrated into the LLRF feedback *** algorithm can prevent undesired regulations in LLRF *** analysis revealed that some burst-noise events did not exhibit measurable energy *** contrast,the other events were accompanied by a rapid loss of cavity stored energy and exhibited similarities to the‘‘E-quench’’phenomena reported in other laboratories.A particle-in-cell simulation indicated that the suspected E-quench phenomenon may be related to a plasma formation process inside the ***,the LLRF algorithm is robust to the two different types of burst-noise events and can significantly mitigate the corresponding cavity faults in CAFe beam commissioning.

关键词： Field emission Flashover E-quench Superconducting LLRF CAFe plasma formation

Terahertz emission in tenuous gases irradiated by ultrashort laser pulses

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Chinese Physics C 2009年第S2期33卷 142-145页

作者：王伟民盛政明武慧春陈民李春张杰 K. Mima Beijing National Laboratory of Condensed Matter Physics Institute of Physics CAS Department of Physics Shanghai Jiaotong University Max-Planck-Institut fr Quantenoptik Institut fr Theoretische Physik I Heinrich-Heine-Universitt Dsseldorf Institute of Laser Engineering Osaka University 2-6 Yamadaoka Suita

Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed.

关键词： Terahertz emission ionization of gases plasma formation particle-in-cell simulations