MAGNETIC PROBE MEASUREMENTS OF THE INITIAL PHASE IN A PLASMA-FOCUS DEVICE

Measurements with magnetic probes performed in the initial phase of a plasma focus device (30 kV, 10.5 mu F) in the pressure range 0.5-5 mba r deuterium are presented, and an interpretation of the obtained signa ls is given, which includes a procedure for disentangling the effect o f variations in the discharge current from the signals. Thick current sheaths, essentially filling all the space between the electrodes, are shown to form at all pressures, travelling radially outwards at const ant speeds of between 2.5 and 3.4 cm mu s(-1). Experimental confirmati on of a theoretical prediction of distortions in the registered signal s due to current exclusions by the probe's body is given, and evidence confirming the 'inverse skin' effect is presented.