Plasma Relaxation in a Reversed Field Pinch Experiment

The time evolutions for the magnetic energy U_m, the magnetic helicity K, and the total helicity K_total with high pinch factor operation of reversed field pinch experiments on S WIP-RFP device are quantitatively calculated. It is shown that U_m and K increase with increasing plasma current but K_total decreases. The results are analyzed and valuable information for the operation is obtained.