Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion

Abstract

The Sphinx machine [F. Lassalle et al., “Status on the SPHINX machine based on the 1microsecond LTD technology”] based on microsecond linear transformer driver (LTD) technology is used to implode an aluminium wire array with an outer diameter up to 140mm and maximum current from 3.5to5MA. 700to800ns implosion Z-pinch experiments are performed on this driver essentially with aluminium. Best results obtained before the improvement described in this paper were 1–3TW radial total power, 100–300kJ total yield, and 20–30kJ energy above 1keV. An auxiliary generator was added to the Sphinx machine in order to allow a multi microsecond current to be injected through the wire array load before the start of the main current. Amplitude and duration of this current prepulse are adjustable, with maxima ∼10kA and 50μs. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. Total power was multiplied by a factor of 6, total yield by a factor of 2.5 with a reproducible behavior. This paper presents experimental results, magnetohydrodynamic simulations, and analysis of the effect of such a long current prepulse.

Numerical studies of the effects of precursor plasma on the performance of wire-array Z-pinches

“…However, it can capture the enough physics of a Z-pinch implosion plasma because the azimuthal inhomogeneities are second order as far as the macroscopic implosion performance and radiation pulse are concerned. 43 In addition, it permits a high efficiency of computation required for investigation of a large of cases. More importantly, we currently study the effects of the precursor plasma on the macroscopic implosion performance of the wire-array Z-pinch mainly through the comparisons of the calculated results, which all are obtained from the same and relatively accurate physical models and coefficients used.…”

Study of the core-corona structure formed during the explosion of an aluminum wire in vacuum

“…Therefore, investigations of the physical processes accompanying the initial stage of electric explosion of fine wires is important for understanding the forma tion process of plasma loads in Z and X pinch exper iments [1][2][3][4][5]. Experiments carried out on the SPHINX facility [6], in which the optimal compres sion and maximum X ray yield were achieved by vary ing the prepulse parameters, as well as experiments with a controllable prepulse on the MAGPIE facility [7], which were aimed at increasing the implosion effi ciency, can serve as examples.…”

Ablation Studies of Low-Number Wire Arrays at 200 kA Using A Linear Transformer Driver

“…A full description of the generator optimization and operation will be presented in a future publication. While the long rise Sphinx LTD generator (6 MA, 1 μs) has been used to drive wire arrays [12] and short rise-time LTD units have been used to test x-pinch loads [10], the data presented in this paper represents the first cylindrical and conical wire-array z-pinches to be examined using a short rise-time LTD driver.…”