Spectroscopic investigations of a planar microsecond POS

Summary form only given. We study the operation of a planar microsecond plasma opening switch in which a current of 180 kA is generated by a low inductance generator and is conducted by the plasma during 400-600 ns before opening into an inductive load within /spl ap/80 ns. The POS region is prefilled with a flashboard plasma of an electron density of 8/spl plusmn/2/spl times/10/sup 14/ cm/sup -3/. Local spectroscopic measurements are obtained by doping the plasma with various species using molecular beam injection through holes in the cathode. Spatial resolution in three dimensions is obtained by observing the characteristic emission of the doped particles perpendicular to the beam. The doped column was seen to have a FWHM of /spl ap/1 cm and a density around 1/spl times/10/sup 14/ cm/sup -3/. Using this method we obtained a 3-D map of the local velocity distributions of helium, neon, and argon doped in the plasma from Doppler broadenings and shifts of their spectral lines. The velocities were seen to scale as z/m and were all much lower than the Alfven velocity. The magnetic field spatial distribution was obtained from Zeeman splitting of helium lines and the magnetic field was seen to penetrate into the plasma at a velocity of 3/spl times/10/sup 7/ cm/s. The electron temperature, studied from comparison of the measured intensities of spectral lines from highly excited states of various ions with collisional-radiative calculations, was seen to increase sharply in the 2.5-cm wide current channel. This will be further investigated for studying the energy dissipation associated with the magnetic field penetration into the plasma.