Present status of plasma focus research at RRC "Kurchatov Institute"

Summary form only given. The experiments at RRC were carried on two identical machines ISPF and PFE (W/spl les/100 kJ) as well as on PF-3 (W=1 MJ). PF chambers were filled with D/sub 2/, Ne and Ar mixtures; the central part of the anodes have Cu, Mo, W and/or Ta inserts. X-ray spectra (HXR: 20-100 keV and SXR: -1 keV) were measured with sub-nanosecond time resolution. The pinch dynamic was diagnosed by the use of the high speed multi-frame photography and X-ray chronography allowing to relate the volumetric and temporal characteristics of a SXR-radiation with the plasma current sheath dynamics at a compression stage. The conversion of a quasi-static accelerating electric field into a ring-like expanding CZ was identified. It was found that the current break process is damped due to a self-regulating current flow around the area with a reduced electric conductivity emerging under explosive anode surface evaporation. CZ-expansion limits the voltage drop across a ring-like transition layer (plasma diode) and explains observed quasi-stationary conditions of electron and ion acceleration. For flux density /spl ges/10/sup 13/ W/cm/sup 2/ an explosive evaporation of the anode material is accompanied by the chipping destruction of a rear electrode surface and provides the ion flux injection into the acceleration zone.