Numerical simulations of the electromagnetic flux compression experiments at the Megagauss Science Laboratory at ISSP

Abstract

The International MegaGauss Science Laboratory at the Institute for Solid State Physics, (ISSP) Japan, conducts experiments on magnetic flux compression by liners [1]. Magnetic fields produced in these experiments currently reach 700 T and break laboratory-scale records. We have conducted 1D numerical simulations of magnetic flux compression under these experimental conditions to determine distributions of parameters across the liner and correlations between resulting magnetic fields and parameters of the liner (thickness and velocity) and seed magnetic field, and to calculate characteristics of plasma, which is predicted [2, 3] to form in such megagauss fields. Our simulation results verify generation of 6-7 MG range magnetic fields in the experiments by Takeyama [1]. In the 1D simulations, as distinct from the experiments, the resulting magnetic fields grow with decrease in the seed magnetic field, which in the simulations is attributed to the fact that the level of magnetic energy produced is controlled by the kinetic energy of the liner and is a weak function of the seed field. Consequently, with decrease in the seed magnetic field, the minimum radius of the liner decreases, and the maximum magnetic field increases. In addition, increase in the liner velocity in the simulations (even for a thinner liner with the same kinetic energy) also leads to higher magnetic fields, which is not observed in the experiments, either. One can suppose that these contradictions between simulation and experiment are related to the development of magnetohydrodynamic instabilities, which produce a compression picture different from 1D. The simulations have also demonstrated that plasma, the temperature of which turns out to be on the order of 20 eV at maximum compression, forms on the inside liner surface (magnetic field/matter interface) starting from a ~360 T magnetic field.