Liner-on-plasma system near stagnation: Stabilizing effect of a magnetic cushion

This brief communication is concerned with the adiabatic compression of a high-beta plasma by a heavy liner. Elongated cylindrical and quasi-cylindrical geometries are considered. The magnetic field in a plasma is parallel to the axis, whereas the drive field has azimuthal direction. During the liner acceleration, the most dangerous modes are axisymmetric (m = 0) modes. Near stagnation, these modes are further amplified at the inner surface, as the liner is decelerated by the isotropic pressure of a high-beta plasma. This picture, however, is not complete: due to a heat loss from the plasma core to the relatively cold liner, a zone of a strong axial magnetic field may appear between a hot, high-beta plasma and a cold liner. This magnetic cushion is backed from inside by a very high-beta plasma. The stability of such a system with respect to m = 0 modes is studied and the conclusion is drawn that the stabilizing effect of the magnetic cushion remains strong even for relatively thin cushions and moderate magnetic fields in them.