Simulation of Isentropic Compression of Aluminum by Magnetically Imploded Liners in experiments ALT-1-3

High precision measurements of accelerated liner velocities (by optical velocimetry VISAR, PDV) produce high-resolution isentropes of test materials - pressure-density curves in the whole range of pressures reached in a single shot [1]. Their interpretation requires solving an inverse mathematical problem by Iterative Lagrangian Analysis (ILA) methods. But in case of magnetic implosion of liners, when the highest isentropic pressures are generated by cumulation, application of such methods presents difficulties. In this paper, we use a similar method of inverse solution with optimization: a small number of parameters are varied to reach the best match between the experimental velocity of the inner liner boundary and the velocity obtained by 1D magnetohydrodynamic calculations. As an example we consider the implosion of aluminum liners having a radius of 4cm and thickness of 2-3mm driven by currents up to 30-75MA (azimuthal magnetic field up to 2-10MG) delivered by ALT-1-3 devices [2]–[3], when liner velocities and isentropic pressures in aluminum reach 12-40km/s and 0.2-8Mbar. Inner liner surface velocities measured by VISAR in the ALT-1,2 experiments reached 12 km/s. The resulting isentrope of aluminum is close to the experimental data available. Accuracy specifications for liner velocity measurements up to 40 km/s in the developed ALT-3 driver were discussed.