Chang C, Verboncoeur J, Guo M N, Zhu M, Song W, Li S, Chen C H, Bai X C, Xie J L
Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China and Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China and Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
Department of Electrical and Computer Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Dec;90(6):063107. doi: 10.1103/PhysRevE.90.063107. Epub 2014 Dec 9.
The time- and space-dependent optical emissions of nanosecond high-power microwave discharges near a dielectric-air interface have been observed by nanosecond-response four-framing intensified-charged-coupled device cameras. The experimental observations indicate that plasma developed more intensely at the dielectric-air interface than at the free-space region with a higher electric-field amplitude. A thin layer of intense light emission above the dielectric was observed after the microwave pulse. The mechanisms of the breakdown phenomena are analyzed by a three-dimensional electromagnetic-field modeling and a two-dimensional electromagnetic particle-in-cell simulation, revealing the formation of a space-charge microwave sheath near the dielectric surface, accelerated by the normal components of the microwave field, significantly enhancing the local-field amplitude and hence ionization near the dielectric surface. The nonlinear positive feedback of ionization, higher electron mobility, and ultraviolet-driven photoemission due to the elevated electron temperature are crucial for achieving the ultrafast discharge. Following the high-power microwave pulse, the sheath sustains a glow discharge until the sheath collapses.
利用纳秒响应四帧增强型电荷耦合器件相机观察了电介质 - 空气界面附近纳秒高功率微波放电的时空相关光发射。实验观察表明，在电介质 - 空气界面处形成的等离子体比在具有更高电场振幅的自由空间区域更为强烈。微波脉冲后，在电介质上方观察到一层强烈的发光薄层。通过三维电磁场建模和二维电磁粒子模拟分析了击穿现象的机制，揭示了在电介质表面附近形成了一个由微波场的法向分量加速的空间电荷微波鞘层，显著增强了局部场振幅，从而增强了电介质表面附近的电离。电离的非线性正反馈、较高的电子迁移率以及由于电子温度升高而产生的紫外驱动光发射对于实现超快放电至关重要。在高功率微波脉冲之后，鞘层维持辉光放电直到鞘层坍塌。
