ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The dynamics of long-conduction-time (τc∼1 μs) plasma opening switches (POS) is studied using magnetohydrodynamic (MHD) theory, including the Hall term. Plasma switches with initial electron densities of ne=1014–1016 cm−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 μs). The conduction times obtained from the simulation studies are in the range τc(approximately-equal-to)0.4–2.0 μs. 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 (ne(approximately-greater-than)1015 cm−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 (ne〈1015 cm−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., Vi=0). The simulation results are consistent with experimental data for conduction currents 300–800 kA.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.870493
