Interferometric investigation of a cablegun plasma injector

A two-beam interferometer operating in heterodyne mode was used to determine the velocity and electron number density of a plasma ejected from a cablegun identical to those in the plasma opening switch (POS) of the DECEDE pulsed power facility. Time-resolved data were processed via digital phase demodulation techniques to measure electron number density at the two beam locations. Cross-correlation analysis of the two signals provided objective estimates of the effective plasma velocity. Experiments were carried out in unobstructed vacuum and near a flat ungrounded conducting plate to examine the plasma in vacuum and its buildup against the POS cathode.