Estimation of the Al Metal-Puff Density Profile on the Generator GIT-12

Experiments on imploding metal-puff Z pinches with an outer plasma shell were performed at currents of 2–3 MA on the GIT-12 generator (4.7 MA, $1.7 \mu \mathrm{s}$) at the Institute of High Current Electronics (Tomsk). The outer plasma shell was produced by 48 plasma guns arranged in a circle of diameter 35 cm. The pinch plasma was generated by a vacuum arc which operated in a gap between an aluminum cathode and an aluminum anode. The initial mass density profiles of metal-puff pinches generated in different load configurations were estimated from experimentally obtained current and voltage waveforms, signals of magnetic probes, and images taken with a streak camera and an HSFC Pro four-frame optical camera. For radii $R$ larger than 0.2 cm, the initial radial mass density profile of a metal-puff pinch was approximated by three Gauss functions. The central part of the pinch with R < 0.2 cm was formed by an aluminum plasma jet with a uniform density. The density profiles in the adjacent jet region (0.2 < R < 2 cm) were provided by the contribution of the aluminum ions from the vacuum arc anode. The next density profile (2 < R < 14 cm) was probably determined by the mass contribution from the surface of the insulator near which the vacuum arc operated. The density peak at the periphery (14 < R < 16 cm) occurred due to the operation of the plasma guns at the diameter of 35 cm.