INVESTIGATION OF ACCELERATION MECHANISMS IN MPD ACCELERATORS

Results are reported from two major phases of this program: (a) consistency tests of induction velometry and determination of radial profiles of the flow velocity, and (b) determination of electric current distribution in the MPD accelerator. The consistency tests are basically aimed at verifying experimentally the validity of the basic relation in induction velometry. Then, a technique based on induction velometry is developed, analyzed, and applied to the determination of radial profiles of the flow velocity. This technique requires probing of the motionally induced potential versus the radius with adequate radial resolution. From such measurements, the radial profiles are determined by a method based on small but finite differences. Many examples are presented and analyzed. The errors of the method are also discussed. The electric current distribution in the accelerator and the nature of the discharge were investigated with sufficient spatial and temporal resolution, using appropriately arranged, floating electrostatic probes. The experimental conditions here were extended over very wide ranges, namely, Gases: H2, D2, He, NH3, N2 and A at flow rates ranging from 0.005 to 0.250 gm/sec, currents from 200 to 2000 amperes and externally applied B fields from 0 to 2500 gauss. (Author)