Spectroscopic characterization and imaging of laser- and unipolar arc-induced plasmas

Tungsten plasmas induced by unipolar arcs were investigated using optical emission spectroscopy and imaging, and compared with laser-induced tungsten plasmas. The unipolar arcs were initiated in the linear-plasma simulator PISCES-A at UCSD under fusion relevant conditions. The electron temperature and density of the unipolar arc plasmas were in the range 0.5-0.7 eV and 0.7-2.0 x 10(20) m(-3), respectively, and increased with increasing negative bias voltage, but did not correlate with the surface temperature. In comparison, the electron temperature and density of the laser-induced plasmas were in the range 0.6-1.4 eV and 7 x 10(19)-1 x 10(22) m(-3), respectively.