Effect of limiter biasing on plasma MHD-stability in GDT device

Radial electric field can essentially alter plasma MHD-stability in a long axisymmetric mirror traps stabilized by remote MHD-anchors. In particular, estimate show that for the Gas Dynamic Trap (GDT), the radial electric field is essential comparing with magnetic field curvature effects. Influence of the radial electric field on the MHD-stability was studied in the GDT using a set of electrically biased radial limiters and segmented end walls. That provides a control of the radial profile of ambipolar potential. It was shown that biasing the peripheral end wall section to a potential of ∼150 V leads to considerable increase of the energy confinement time due to reduction of the electric field in the plasma volume. The MHD-stability boundary was significantly modified. Possible stabilization mechanism is considered in the paper. (author)