The roles of plasma rotation and toroidal field ripple on the H-mode pedestal structure in JT-60U

Abstract

By conducting power scan experiments in three cases of toroidal field ripple configurations (δr ≃ 0.4, 1.0 and 2.0%) with variation of the toroidal momentum source (co, balanced, counter) relative to the direction of the plasma current, the roles of the loss of fast ions and toroidal rotation on the H-mode pedestal structure were investigated. It was found that the pedestal pressure was increased with a decrease in fast ion loss power. On the other hand, the variation in toroidal rotation did not affect strongly the pedestal pressure, although the loss of fast ions due to existing large toroidal field ripple forced the toroidal rotation basically to the counter direction in JT-60U. Due to the enhanced counter toroidal rotation induced by the loss of fast ions, similar Vtor profiles were obtained for discharges with different toroidal momentum source and loss of fast ions. When the loss of fast ions became smaller, pedestal density was raised remarkably while there was no significant difference in the temperature profiles.