Search

The first pellet refuelling of a reversed field pinch has been successfully demonstrated in ZT-40M. By injecting a series of pellets, density increases of 600% have been observed, with no disruptions. Because of a coincidence of pellet transit time, Ohmic reheat time and particle confinement times (about 0.5 ms) a significant fraction of the plasma inventory 'leaks out' before pellet ablation is complete. Strong on-axis peaking of the density profile due to pellet fuelling is not typically observed; this is due to large poloidal and toroidal deflections observed in the pellet trajectory, beginning in the plasma edge. Asymmetric ablation of the pellet by a suprathermal electron population is suspected and simple modelling can account for the observed trajectories.

Reversed-field pinch configurations produced in the OHTE device using a resistive shell were maintained for up to 7.5 times the shell resistive time. The plasma density, resistance, and magnetic fluctuations do not evolve significantly while the plasma current is sustained, and the plasma behaviour is similar to that previously observed in conducting shell OHTE/RFP experiments. The experimental observations suggest that a highly conducting shell may not be required for the stability of a reversed-field pinch.