The Generation of Warm Dense Matter Samples Using Fast Magnetic Compression

Abstract

Our understanding of warm dense matter (WDM) properties will help to unravel the formation and evolution of giant planet, including gaseous giants or mega-Earths. However, the production of WDM in the laboratory is limited to samples on the order of tens of micrometers. This raises many challenges to measure the properties of WDM using standard diagnostics. In this paper, we propose a new method to produce WDM samples using pulsed-power machines. We numerically demonstrate that the early expansion phase of the sample, usually encountered in pulsed-power systems, can be virtually eliminated using a current switching scheme. To avoid mixing the plasma and WDM states, the present strategy uses a gas-puff $Z$ -pinch as a closing plasma switch. During the first part of the discharge, most of the current flows inside a gas-puff $Z$ -pinch, preventing the heating of the sample. During this phase, the gas $Z$ -pinch radially converges toward the sample. When the $Z$ -pinch finally reaches the sample, all the $Z$ -pinch current switches to the sample and rapidly heats it. The strong azimuthal field generated by the $Z$ -pinch prevents the expansion of the sample. If the initial gas pressure is carefully chosen, the sample reaches a quasi-homogeneous WDM state. The efficiency of the method allows one to produce millimeter-size WDM samples with a 500-kA pulser.