Screw pinch with reversed force-line pitch

A screw pinch in which the pitch of the lines of force is reversed through a ''translational transformation'' has been studied analytically and numerically. (The configuration is of the OHTE type, proposed by T. Ohkawa.) The monotonically decreasing profile of q (the safety factor) required for stability, with q reversing at the plasma boundary, can be created in such systems even in the complete absence of poloidal currents in the plasma. The steady-state screw pinch is studied, and it is shown that the reversal of q in it is compatible with the ordinary Ohm's law. The reversal of q in a screw pinch does not require a reversal of the longitudinal field, as in an axisymmetric pinch. The reversal of q in the steady state is simplified substantially if the plasma conductivity increases at the periphery, e.g., as a result of heating