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arXiv 1503.00386physics.plasm-ph
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实验室低压等离子体中孤电子空穴的瞬态演化

Transient evolution of solitary electron holes in low pressure laboratory plasma

Mangilal Choudhary, Satyananda Kar, Subroto Mukherjee

摘要:

孤立电子空穴是无碰撞等离子体中的一种局域化静电正势结构。这些是电子相空间中的涡旋状结构。它的存在是导致共振区电子分布畸变的原因。Schamel第一次从理论上解释了这些。et.al 20,336(1979)和Phys.Plasmas 19,020501(2012)]。当向金属电极施加快速上升的高正电压脉冲时,也可以在实验室等离子体中形成孤立的电子空穴[Kar et.例如,等离子体物理17,102113(2010)]。这些结构的时间演化可以通过测量瞬态电子分布函数(EDF)来研究。在目前的工作中,瞬态EDF测量后,形成一个孤立的电子空穴在几乎均匀的,未磁化的,和碰撞的等离子体施加的脉冲宽度和,其中和施加的脉冲宽度和离子等离子体频率的倒数分别。对于这两种类型的脉冲宽度,双峰状的瞬态EDF的轮廓观察,表明孤立的电子空穴存在于系统中的时间周期长于所施加的脉冲持续时间。束(或自由)电子与捕获(或体)电子一起给出了等离子体中SEH的解决方案。没有自由电子或束电子,就不存在SEH。瞬态EDF测量揭示了等离子体中SEH的存在和演化。测量结果表明,在低压范围内,这些结构在系统中的生存时间较长。在高压情况下,只观察到单个驼峰状瞬态EDF,即只捕获或大量电子。在这种情况下,在施加脉冲结束后等离子体的演化期间,SEH不存在于等离子体中。

英文摘要:

Solitary electrons holes (SEHs) are localized electrostatic positive potential structures in collisionless plasmas. These are vortex-like structures in the electron phase space. Its existence is cause of distortion of the electron distribution in the resonant region. These are explained theoretically first time by Schamel et.al [Phys. Scr. 20, 336 (1979) and Phys. Plasmas 19, 020501 (2012)]. Propagating solitary electron holes can also be formed in a laboratory plasma when a fast rising high positive voltage pulse is applied to a metallic electrode [Kar et. al., Phys. Plasmas 17, 102113 (2010)] immersed in a low pressure plasma. The temporal evolution of these structures can be studied by measuring the transient electron distribution function (EDF). In the present work, transient EDF is measured after formation of a solitary electron hole in nearly uniform, unmagnetized, and collisionless plasma for applied pulse width and, where and are applied pulse width and inverse of ion plasma frequency respectively. For both type of pulse widths, double hump like profile of transient EDF is observed, indicating that solitary electron hole exists in the system for time periods longer than the applied pulse duration. The beam (or free) electrons along with trapped (or bulk) electrons gives the solution of SEHs in the plasma. Without free or beam electrons, no SEHs exist. Transient EDF measurements reveal the existence and evolution of SEHs in the plasma. Measurements show that these structures live in system for longer time in the low pressure range. In high pressure cases, only single hump like transient EDF is observed i.e. only trapped or bulk electrons. In this situation, SEH does not exist in the plasma during evolution of plasma after the end of applied pulse.

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