Properties of hot-spots in Plasma Focus discharges operating in Hydrogen-gas mixtures

We have investigated the properties of hotspots formed in low energy Plasma Focus discharges operating in Hydrogen-Argon mixtures, at 140 kA current level. The results show that best conditions for reproducible and localized hotspot formation are obtained by adjusting the base pressure in such a way that the mass load allows the time of first radial collapse to coincide with peak current. When the Plasma Focus is operated with 20% Argon content, rather uniform hotspots, of 115 µm characteristic size and 300 eV characteristic temperature, are produced with a better than 80% reproducibility in their axial localization. A significant fraction of the radiation is emitted in the 3.2 to 3.88 keV region, corresponding to Kα emission from highly ionized Argon.