Magnetic field and electrode geometry effects on vehicle discharging by neutral gas release

In earlier work we quantified the effect of the Mach number of neutral gas release and neutral gas species on minimum breakdown potential in ionospher ic-like plasmas. The theoretical basis of this work incorporates the Townse nd breakdown criterion to the ambient plasma to characterize the discharge. The results of a model based on this theory provide good agreement with th e results of experiments in a variety of gases performed in the large Space Physics Simulation Chamber (SPSC) at the Naval Research Laboratory. The ex periments in the SPSC used a 10 cm x 10 cm aluminum cylinder which containe d a neutral gas release valve and variable Mach number nozzles. The cylinde r was charged to high negative potential before neutral gas was released, c ausing breakdown to the ambient plasma for sufficient valve plenum pressure . We have recently incorporated both electrode geometry design changes and an external magnetic field produced by a permanent magnet in an effort to l ower the breakdown voltage required. We have preliminary results which sugg est that both an extended smaller cylinder and an external magnetic field c an significantly lower the potentials required for breakdown. We are in the process of verifying these results by adding an adjustable constant magnet ic field both perpendicular and parallel to the gas release direction.