Dynamics of downstream plasma in the plasma opening switch

The paper is devoted to the physical aspects of plasma opening switches (POS). It has been demonstrated that POS operation is governed not only by the processes in the plasma-filled POS region but also by the rarefied plasma which appears in the downstream region. The expansion of this plasma towards the downstream load determines typical time of the POS opening. In experiments with POS (I/sub POS//spl sim/35 kA, T/sub 1/4//spl sim/300 ns) high-energy electron beam generation has been observed in the region downstream with respect to the load. It has been shown that such a beam is accompanied by ions having energies several times higher than the electron energies. It has been shown that these ions were accelerated from the load side edge of the plasma. The beam appearance occurred almost simultaneously with the beginning of the inductive voltage. The paper attracts especial attention to the conduction phase of a high-impedance POS (I/sub g//spl sim/170 kA, U/sub g//spl sim/180 kV, I/sub l//spl sim/10 kA, U/sub l//spl sim/700 kV). Results of nonlinear magnetic field and current penetration into the downstream plasma are reported. An effect of the acceleration and broadening of the penetrating wave of convective field/current transport in the downstream region has been observed. This effect has been explained on the base of electron magnetohydrodynamics (EMHD) combined with the effect of plasma anomalous resistivity conditioned by the current-driven ion-acoustic instability resulting from the high current flow velocity in the downstream region.