(EX/P5-25) High β Plasma in Improved Confinement Regime on the TPE-RX Reversed-Field Pinch Plasmas

H. Koguchi1), H. Sakakita1), Y. Hirano1), K. Yambe1), L. Frassinetti1), F. Auriemma2), D. Terranova2), P. Innocente2), S. Kiyama1), T. Shimada1)
1) National Institute of Industrial Science and Technology, Tsukuba, Japan
2) Consorzio RFX, I-35127 Padua, Italy

Abstract.  A very high poloidal β was achieved by the Pulsed Poloidal Current Drive (PPCD) in Toroidal Pinch Experiment-RX (TPE-RX, was operated to March 2007 from April 1998). The plasma electron density and temperature increased, hence, the poloidal β was improved to 30% from 5% during PPCD (poloidal β is almost equal to total β in the reversed-field pinch). Dα emission from recycling deuterium by the plasma-wall interaction decreased during the PPCD and the ratio of the total number of particles to the Dα emission increased ten-fold at the end of the PPCD with a resulting improvement of the particle confinement time. Fast magnetic fluctuation levels in the edge region of TPE-RX were measured using a newly developed complex edge probe installed inside a vacuum vessel and sensitive to fast magnetic fluctuation. During the PPCD operation, the magnetic fluctuation associated with the dynamo effect is reduced, and improved confinement is reached, which results in this high β value. Unique NBI system suitable for the RFP machine was developed to control plasma parameters. In the case of high power neutral beam injection to the improved confinement plasma which was attained by PPCD operation with an ice pellet injection, the meaningful increments in the soft X-ray signal and the plasma current were found.

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