Anode Plasma Density Measurements in a Magnetically Insulated Diode

The surface-flashover anode plasma in a magnetically insulated ion diode was investigated spectroscopically. From the Stark broadening of the neutral hydrogen ${\mathrm{H}}_{\beta }$ line an average electron density of about 2×${10}^{15}$/${\mathrm{cm}}^3$ was observed in the ≲ 1-mm anode plasma, 30 nsec into the 400-475-kV diode voltage pulse. Thereafter, the plasma front advanced into the diode gap at an average rate of 2 cm/μsec. This may be explained by the ionization of neutral atoms injected into the gap during flashover.