Nonlinear behavior of the reversed field pinch with nonideal boundary conditions

The effect of a resistive boundary and/or a distant conducting wall on a reversed field pinch is investigated with a three-dimensional magnetohydrodynamics code. Fluctuations rise with increasing distance between the conducting wall and the plasma. The enhanced fluctuation-induced v×{}b electric field primarily opposes toroidal current; hence loop voltage must increase to sustain the current. This increases the helicity injection rate, which is balanced by an enhanced surface loss.