Interferometer density measurements of a high-velocity plasmoid

The plasmoid produced by a half-scale contoured gap coaxial plasma accelerator using ablative polyethylene capillary plasma injectors is measured using a quadrature heterodyne HeNe interferometer. The plasmoid is found to have a sharp rise in density at the leading edge, with a gradual falloff after the peak density. For this early test series, an average bulk density of 5 × 10 14 cm − 3 is observed, with densities up to 8 × 10 14 cm − 3 seen on some shots. Although plasmoid mass is only about 58 μ g due to the low current and injected mass used in these tests, good shot-to-shot repeatability is attained making analysis relatively straightforward, thus providing a solid foundation for interpreting future experimental results.