Hall magnetohydrodynamic modeling of a long-conduction-time plasma opening switch

Journal Article · Sat Oct 01 04:00:00 EDT 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870493· OSTI ID:6684684

Huba, J D; Grossmann, J M; Ottinger, P F ^[1]

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1. Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

The dynamics of long-conduction-time ([tau][sub [ital c]][similar to]1 [mu]s) plasma opening switches (POS) is studied using magnetohydrodynamic (MHD) theory, including the Hall term. Plasma switches with initial electron densities of [ital n][sub [ital e]]=10[sup 14]--10[sup 16] cm[sup [minus]3] are modeled; these densities are appropriate to recent experiments carried out at the Naval Research Laboratory using the Hawk generator (800 kA, 1.2 [mu]s). The conduction times obtained from the simulation studies are in the range [tau][sub [ital c]][congruent]0.4--2.0 [mu]s. The POS plasma is strongly redistributed by the penetrating magnetic field. As the field penetrates, it pushes the plasma both axially and radially (i.e., toward the anode and cathode). In the higher-density regime ([ital n][sub [ital e]][gt]10[sup 15] cm[sup [minus]3]), Hall effects do not play a significant role. The magnetic field acts as a snowplow, sweeping up and compressing the plasma as it propagates through the POS plasma. In the lower-density regime ([ital n][sub [ital e]][lt]10[sup 15] cm[sup [minus]3]), Hall effects become important in two ways: the conduction time is less than that expected from ideal MHD, and the POS plasma becomes unstable as the magnetic field penetrates, leading to finger-like density structures. The instability is the unmagnetized ion Rayleigh--Taylor instability and is driven by the magnetic force accelerating the plasma. The structuring of the plasma further decreases the conduction time and causes the penetrating magnetic field to have a relatively broad front in comparison to EMHD simulations (i.e., [bold V][sub [ital i]]=0). The simulation results are consistent with experimental data for conduction currents 300--800 kA.

• OSTI ID: 6684684
• Journal Information: Physics of Plasmas; (United States), Journal Name: Physics of Plasmas; (United States) Vol. 1:10; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700370* -- Plasma Fluid & MHD Properties-- (1992-)
EIGENVALUES
ELECTRICAL EQUIPMENT
ELECTRON DENSITY
EQUIPMENT
FLUID MECHANICS
HALL EFFECT
HYDRODYNAMICS
INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL OPERATORS
MECHANICS
PLASMA SWITCHES
RAYLEIGH-TAYLOR INSTABILITY
SWITCHES
WKB APPROXIMATION