Time-resolved spectroscopic characterization of the pseudospark-discharge plasma

The high-current discharge in a pseudospark geometry can be subdivided in several phases. While the first and the last ones are well understood, the plasma parameters as well as the current carrying mechanisms of the phases in between are still subject of investigations. Different temporally resolved spectroscopic measurements of the localized copper vapor plasma were performed. The electron densities, measured by Stark broadening of the H-β line, are between 14¹⁴ and 10¹⁶ cm^-3. The electron temperature was determined by the intensity ratio of atomic to ionic copper lines. It was taken into account that the plasma was not in local thermal equilibrium. Estimations of the main equilibrium and nonequilibrium processes allowed to correct the measured temperature values. During the bore-hole phase, the corrected temperatures are between 1.5 and 2.5 eV. During later phases, the discharge plasma is self absorbing and less reproducible for the plasma parameters to be determined. The plasma parameters indicate that the current between the localized copper plasma sheet and the cathode is mainly carried by positive ions. Electron emission is mainly caused by ion impact and is only of inferior significance for the current balance.