Field error and its effect on the plasma performance in TPE-RX, reversed-field pinch device

The effects of field errors at the poloidal gap of the thick shell on the p lasma performance and the wall-locking are intensively studied. The coil sy stem of TPE-RX (major/minor radii, R/a = 1.72/0.45 m) has several features for cancelling the field errors at the thick shell gap and for controlling the equilibrium position of the plasma column. It is confirmed that these f ield error cancellation schemes work well for the normal operating conditio ns in TPE-RX. It is shown quantitatively that the global performance of the revised-field pinch operation is affected if the shell gap field error exc eeds about 5% of the poloidal magnetic held. As expected, the probability o f the mode to lock at the shell gap increases as the field error increases.