CURRENT SHEATH STUDIES BY MAGNETIC PROBES ON PLASMA FOCUS PF-400

The time resolved studies of the current sheath formation in a plasma focus discharge of Filippov type with energy stored in capacitors 60 U and maximum current 0.9 MA are presented. The current data received by two magnetic probes placed at radii 15 and 20 cm were compared with the total current detected by Rogovsky loop. It was found out in discharges with low neutron yield the formation of the extra current sheathes following one after another in 1-th, 2-th and even 3-th half-period of discharge. The single current sheath was observed in the discharges with the high neutron yield. The absolute current measurements showed that the whole discharge current goes throw paraxial area r < 15 cm during the phase of radial implosion, but at the instant of the peculiarity on the current derivative it is no more then half of value of total current. The value of the pinch current remains under the question.