Ion currents in ace 4 upstream of POS during opening

Concern that the plasma remaining upstream of the initial region of plasma injection for the plasma opening switch may adversely impact the performance of the switch has motivated investigation of the properties of this residual plasma. Here a model is introduced and calculations performed to compare with Faraday cup measurements (see Fig. 1) of ion currents in the residual plasma during the high voltage pulse following the end of the conduction phase¹⁾. This model complements the model for ion currents in the conduction phase reported previously reported²⁾. The calculations are based on the assumption that ions are generated by electron impact ionization of neutrals residing in upstream locations (Fig. 2). The electrons acquire their energy from the switch voltage in the form of an E×B drift in the magnetic field of about seven tesla that exists at the onset of opening.