Radiative Characteristics of Al Metal-Puff Z-Pinches in Experiments on the GIT-12 Generator at a Microsecond Implosion Regime

Abstract

Study of radiative characteristics of Al metal-puff Z-pinches has been carried out in the experiments on the GIT-12 generator. The generator was operated in a microsecond mode that provides 4.7-MA current with the current rise time of $1.7 \mu\mathrm{s}$ in a short-circuit load at a charging voltage of 50 kV. A Z-pinch load under investigation consisted of a metal puff surrounded by a plasma shell. The Al metal puff was created on the axis by evaporation of the electrode substance in a vacuum arc discharge. The outer plasma shell was formed at a diameter of 350 mm with the help of 48 plasma guns. Measurements of the radiation power and yield were carried out with a set of x-ray vacuum diodes and photoconducting detectors. During the experiments, the data on the Al K-shell radiation power and yield were obtained for two different configurations of the Al metal-puff Z-pinches and for a case, when the Al metal puff was used without the outer plasma shell. The experimental data were compared to the theoretical predictions of an expected K-shell yield at a certain current level in order to estimate the efficiency of a new type of K-shell plasma radiation source. Performance of the Al metal-puff Z-pinch with the outer plasma shell as a K-shell plasma radiation sources was also compared with that of the gas-puff-on-wire array and planar wire array loads operating in the microsecond implosion regime. Up to now, the highest Al K-shell radiation power and yield were achieved in our previous experiments with planar wire arrays: 200 GW/cm and 6.5 kJ/cm, respectively. These radiation parameters were reached at the peak implosion current of 3.6 MA. The maximum Al K-shell radiation power and yield observed in the experiments with Al metal-puff Z-pinches with the outer plasma shell were 400 GW/cm and 4.5 kJ/cm, however the peak implosion current was only 2.4 MA. This means that the efficiency of the K-shell plasma radiation source based on the Al metal-puff with the outer plasma shell is significantly higher.