Experimental Generation of Steady-State Strong Shock with Charge Triple-Layer Profile in Laboratory Magnetized Plasma
李宗懋1*, 張皓1, 河森 榮一郎1
1太空與電漿科學研究所, 國立成功大學, 台南市, Taiwan
* Presenter:李宗懋, email:happyfat332@gmail.com
The steady-state collisionless strong shock (∆Vs > Te/e) having a charge triple-layer (TL) structure was discovered in a laboratory magnetized plasma experiment, where ∆Vs, Te/e and e are the potential depth of the shock, the electron temperature and elementary charge, respectively. We experimentally obtained the phase space (v-x) diagram of the electrons and ions in the vicinity of the TL from the Langmuir probe and Mach probe measurements. The TL was accompanied by a density jump by approximately one order. The electron phase space diagram indicated that islands of trapped electrons exist behind the potential dip of TL, which is consistent with a BGK (Bernstien-Greene-Kruskal) picture, namely collisionless pictures rather than hydrodynamic pictures. However, because the present information on the phase space of ions and electrons is insufficient for evaluation of the BGK picture, the following two diagnostic tools are under development: 1) Directional Langmuir probes to measure the directional electron distribution functions, 2) Mach probes at the both side of TL to confirm the energy conservation of ion beam. In the presentation we will show experimental results of these measurements in addition to discussion on controllability of the shock structure with TL in experiment.

Keywords: Bernstein-Greene-Kruskal (BGK) modes, Neutral Magnetized plasma experiment, triple-layer, steady state strong shock, Langmuir probe, Mach probe