Improved Confinement regimes by the Control of Reversal of Toroidal Magnetic Field in the TPE-RX Reversed-Field Pinch Plasmas

Improved plasma performances have been achieved in the reversed field pinch (RFP) experiment on TPE-RX (major/minor radii = 1.72 m/0.45 m, plasma current < 0.5 MA) by the pulsed poloidal current drive (PPCD) and the quasi-single helicity (QSH) state, which were obtained by the control of the reversal of toroidal magnetic field. The steady high density state has been obtained during the PPCD period with a single ice pellet injection, which indicates the drastic (five-hold) increase of the particle confinement time in PPCD compared with the ordinary shots. It has been also found that the better plasma performance is observed in the QSH state compared with the multi-helicity (MH) state, both of which alternatively appear in a single shot under particular operating conditions. It has been demonstrated for the first time that the QSH state can be obtained with an almost 100% probability by applying a small positive pulse to the reversed negative toroidal magnetic field. The result of the high power (~ up to 2 MW) NBI experiment will be presented, which has been connected to the torus and whose injection experiment has been just started.