The Suppression of Core-Corona Structure for Aluminum Wire Array and Its Influence on the Implosion Dynamics Under a Current of Mega-Ampere

Abstract

In order to suppress the core-corona structure (namely, the dense wire core in atomic state surrounded by plasma with high temperature and low density), two-stage wire array experiments have been carried out on Qiangguang-1 generator (1.3 MA and ~80 ns). The results showed that the shutdown time of inverse array, which consists of a central cathode rod surrounded by wires, depended on wire number. The shutdown time was 40 ns after the start of main current, when two aluminum wires were placed in inverse array, which ensured that there was still enough time during main current for load array to implode and radiate X-rays. The vaporized wire cores expanded uniformly along the axis with a smooth boundary and the average wire diameter was 1.8–1.9 mm. The vaporized wire cores were ionized rapidly after the shutdown of inverse array. The perturbations of plasma instability were first observed at the boundary of vaporized core and developed rapidly after the start of implosion. The average wavelength of these perturbations was 600– $650~\mu \text{m}$ . The precursor plasma was barely observed on the array axis in optic images. The X-ray pulse output by vaporized wire array with mega-ampere current was first given. Considering the waveform of X-rays and main current, the pinch process of the vaporized load array tended to the quasi-shell implosion. Nevertheless, there were still some fractions of plasma being left down at the initial position to lead the second implosion for the rapid development of magneto-Rayleigh-Taylor instability in implosion, which resulted in the double peaks of X-rays. The suppression methods of the implosion instability will be further studied and explored in future.