Emission spectroscopic measurements and analysis of a pulsed plasma jet

An investigation has been conducted of the characteristics of a freely expa nding pulsed plasma jet originating from an electrothermal capillary source . The evolution of the plasma jet was investigated using temporally- resolv ed emission imaging with a gated intensified CCD camera and temporally- and spatially-resolved emission spectroscopy. The emission images reveal a hig hly underexpanded plasma jet that forms a distinct barrel shock structure, with a highly luminous Mach disk. The jet structure reaches an approximatel y quasi-steady state about 70 mu s after the initiation of the plasma. An a nalysis of the emission spectra along the jet axis indicates population tem peratures in the expanded region, upstream of the Mach disk, to be 2.02 eV (23 400 K) and 1.4 eV (16 200 K), for time delays of 30 mu s and 70 us, res pectively. At these same time delays, the electron number densities upstrea m of the Mach disk are of order 10(17) cm(-3), but increase by an order of magnitude downstream of the Mach disk. Virtually no change is observed in t he electron density across the Mach disk at a delay of 120 mu s, indicating the shock front has largely dissipated.