Formation and dynamics of plasma layers formed on the foil surface under the action of a high-current pulse

Results are presented from studies of the possibility of using a thin metal foil for recyclable vacuum transmission lines with magnetic insulation in a conceptual fusion reactor based on high-voltage high-current electromagnetic generators. Numerical simulations and experiments in the Angara-5-1 facility were carried out to determine both the threshold for the explosion of a foil heated by a current pulse and the parameters of the plasma layer formed at the foil surface. It was found experimentally that an additional plasma current channel forms on the surface of a 120-μm stainless-steel foil at a linear current density of 0.25–0.5 MA/cm, which corresponds to a magnetic field of 0.3–0.6 MG. For the same conditions, one-dimensional computer simulations of the foil heating were performed in an MHD model by using a wide-range semiempirical equation of state for stainless steel. The calculated threshold for plasma generation on the foil surface is compared with the experimental data. The main parameters of the plasma layer are also calculated at linear current densities of 2–10 MA/cm, which far exceed the threshold current density. The plasma layer parameters as functions of the linear current density are determined for the case of an iron foil.