2D magnetic field evolution and electron energies in plasma opening switches

Summary form only given, as follows. We present measured time dependent 2-D structures of the magnetic field in two plasma opening switches (on 100 ns and 0.5 /spl mu/s time scales), together with an analytical model based on EMHD used to explain the data for the short time switch. The magnetic field, local in 3-D, is obtained by doping the plasma with various species and observing the Zeeman splitting of their spectral lines, using polarization spectroscopy. In the coaxial 100-ns switch, fast (/spl sim/10/sup 8/ cm/s) field penetration with a relatively sharp field front is observed, together with a non-monotonic axial distribution later in the pulse. The model developed, that utilizes the measured 2D plasma density distribution and assumes fast field penetration along both POS electrodes, provides quantitative explanation for the observed field evolution. In the planar 0.5 /spl mu/s switch, a 3-D mapping of the field is obtained. The current channel, 2.5 cm wide, is found to propagate downstream at a velocity /spl sim/3/spl times/10/sup 7/ cm/s. The electron energy in the current channel is studied spectroscopically. The replacement of electrons and the energy dissipation due to the field penetration will be discussed. A comparison of the result for the two time-scale switches and for opposite charging polarities in the coaxial switch will be presented.