Efficiency of the magnetic flux compression by a plasma shell

In the discussed scheme an azimuthal magnetic field is compressed by a plasma liner at the 0.1-1 mks time scale. In this case the liner is accelerated by a magnetic filed provided by an electrical pulse generator. When coupled with existing pulsed power technology, the flux compression can yield further pulse sharpening and power multiplication necessary for achieving the ICF conditions. Besides, application of this particular configuration may represent a new technological challenge in the projects of construction of inductive energy storage generators operating at dozens of MA. Before concrete realizations of the scheme it is important to analyze possible mechanisms limiting the efficiency of the energy transfer into the load. We consider that the magnetic flux may be lost for the load due to the diffusion of the compressed magnetic field into the liner and due to inhomogeneities of the liner inner surface as a consequence of macroscopic instabilities development. Both these effects are studied in two-dimensional numerical simulations with the help of a radiational MHD code coupled to the tables of equations of state, transport and radiative coefficients. In a series of simulations we show that in the framework of the used physical and numerical models a considerable part of the initial flux may rest frozen into the liner plasma at the load current rise time scale. On the contrary, the liner instability has less influence on the flux transfer efficiency. The efficiency found in the simulations strongly depends on the liner compression time and on the value of the initially seeded magnetic flux. The modeling results are compared with theoretical estimations and with the recent experimental data in the light of possible scaling laws when increasing the primary pulsed power.