Coaxial Plasma Gun in the High-Density Regime and Injection into a Helical Field

A modified CPG in the high density regime of 20-70mT of He was investigated. The injection of the plasmatorus into a driftspace was studied by diamagnetical diagnostics both with and without helical bias, where the inner electrode was continued into the driftspace by a central conductor. Quasi-tokamak geometry is obtained (q almost-equal-to 3; l(j) almost-equal-to 1.2; beta(p) almost-equal-to .7). Mean speed of torus in driftspace: 2.2cm/musec; which is in very good agreement with the MHD model derived. Discussion of: (1) general phenomena, (2) second half-period breakdown with autopreionisation, (3) prevention of transv. expansion by rarefaction waves of Mach 50 supersonic flow, (4) stability and homogeneity enhancement, (5) agreement with model, (6) X-points & breakdown dependence. The findings are important for future designs of injectors for magn. confinement.