Energetic ion emission in a positive polarity nanosecond plasma opening switch

We studied the emission of energetic ions from the plasma in a coaxial Plasma Opening Switch (POS) powered by a 300 kV, 15 kA, 90 ns positive polarity pulse. Fluxes lasting 2 – 3 ns of ions flowing radially onto the cathode were seen to occur at all axial locations of the switch plasma within 5 ns of the beginning of the upstream POS current. It is suggested the termination of this ion flux results from the formation of a cathode plasma that is consistent with our spectroscopic measurements. Later in the pulse, longer duration (100 ns) ion fluxes were observed radially, first appearing in the generator side of the switch plasma. Fluxes, 30 – 40 ns long of ions flowing axially towards the POS load at velocities (2±1)×10⁸cm/s were also seen. The dependence of the start time of the axial ion flow, of the ion velocities, and of the ion flux on the POS operation parameters were studied.