Characterization of a microsecond-conduction-time plasma opening switch

Abstract

This paper presents data and analyses from which emerges a physical picture of microsecond-conduction-time plasma opening switch operation. During conduction, a broad current channel penetrates axially through the plasma, moving it toward the load. Opening occurs when the current channel reaches the load end of the plasma, far from the load. During conduction, the axial line density in the interelectrode region is reduced from its value with no current conduction as a result of radial hydrodynamic forces associated with the current channel. A factor of 20 reduction is observed at opening in a small, localized region between the electrodes. When open, the switch plasma behaves like a section of magnetically insulated transmission line with an effective gap of 2 to 3 mm. Increasing the magnetic field in this gap by 50% results in an improvement of 50% in the peak load voltage and load current rise time, to 1.2 MV and 20 nsec, respectively. An erosion opening mechanism explains the inferred gap growth rate using the reduced line density at opening. Improved switch performance results when the maximum gap size is increased by using a rising load impedance.

Energetic electron and ion beam generation in plasma opening switches

“…This indicates that the axial width of the current conduction region is larger than 1 and 3 cm for the NPOS and MPOS, respectively. These widths are much larger than the shock-front thickness predicted by EMHD or MHD theories, but are in agreement with previous results that have shown broad current channels both in the NPOS and MPOS [3]. The larger thickness of the current layer than predicted by the EMHD model may be related to development of plasma instabilities as suggested in a fluid code simulation [20] and indirectly proved by observation of high frequency electric fields during MPOS [25] and NPOS [26] conduction.…”

“…D URING the last 20 years many experimental investigations were devoted to the plasma opening switch (POS) operated in nanosecond (NPOS) [1] and microsecond (MPOS) [2], [3] time scales. Such interest results from the POS potential as the fastest high-current, high-voltage interrupter in inductive energy storage systems and the rich physical phenomena taking place in the current carrying plasma.…”

Nonlinear Phenomena Associated with Large Amplitude Whistler Pulses

“…Furthermore, the weak damping can be ticity, eqn. (2). The axial components are inaccounted for by collisional damping rather than tegrated over the transverse cross section for Landau damping (note that vll E vth,e) [19].…”

“…Applications include plasma opening switches [2], pulsed ion beam propagation across Bo [3], helicon waves [4], electrodynamic tethers in space [5], dissipation processes in narrow current sheets undergoing reconnection [6], plasma releases [7], and wings behind small asteroids in the solar wind [8]. Basic physics experiments have demonstrated that pulsed EMHD currents in magnetized plasmas are transported by whistler waves [9-111.…”

Hall Magnetohydrodynamics - A Tutorial

“…The theory has been successfully applied to the structuring of sub-Alfvénic plasma expansions [1,2,3,4,5,6,7] and to rapid magnetic field transport in plasma opening switches [8,9,10,11,12,13,14,15,16,17]. In recent years it has become evident that Hall physics plays a critical role in magnetic reconnection processes [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36] and this has spurred renewed interest in this subject.…”