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proc_icc2011_masamune.pdf2011-09-09 12:13:32Sadao Masamune
icc2011_masamune.pdf2011-08-28 10:36:07Sadao Masamune

Low-aspect-ratio RFP plasma properties in two characteristic regimes in RELAX

Author: Sadao Masamune
Requested Type: Consider for Invited
Submitted: 2011-06-09 22:01:35

Co-authors: A.Sanpei, K.Oki, S.Fujita, D.Fukabori, H.Himura, N.Nizuguchi, H.Koguchi, D.J.Den Hartog, R.Paccagnella

Contact Info:
Kyoto Institute of Technology
Matsugasaki, Sakyo-ku
Kyoto, Kyoto   606-858

Abstract Text:
The aspect ratio A is one of the important parameters for optimization of the RFP configuration because it affects the q profile and/or fraction of the pressure-driven bootstrap current. RELAX (A=R/a=0.5m/0.25m) is a low-A RFP machine to explore the potential advantages of low-A configurations. The discharge and plasma parameters in RELAX to date are as follows: plasma current up to 100kA, discharge duration of up to 2.5ms, electron density in the range from 0.2 to 2.0 X 10^19 m−3, and electron temperature around 100eV. We describe plasma properties in two extreme discharge regions, i.e., very shallow-reversal and extremely deep-reversal regions attained in RELAX. In very shallow-reversal region where F slightly negative or almost 0, magnetic fluctuation
shows transition to QSH, and helically deformed hot or dense core has been identified using SXR imaging diagnostics. On the other hand, extremely high-Theta (up to ~3.5), deep-reversal (F down to ~ - 1.5 ) regions have been attained without serious discrete relaxation events at the expense of low-density operation. Edge magnetic fluctuation level is lower for the discharges in these extremely deep reversal regions. Behavior of the MHD instabilities will also be discussed based on preliminary results from 3-D MHD simulation for low-A RFP configuration.

Characterization: A3

Being a member of the Japanese delegation for US-Japan CT Workshop, I have to leave on 8/19.

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011