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Investigation of Ideal-MHD Stable Scenario for Plasma Current Ramp-Up with No Magnetic Flux Consumption in JT-60SA

Takuma WAKATSUKI, Takahiro SUZUKI, Nobuhiko HAYASHI, Junya SHIRAISHI, Shunsuke IDE, Hirotaka KUBO and Yuichi TAKASE¹⁾

Japan Atomic Energy Agency, Naka 311-0193, Japan

1)

University of Tokyo, Kashiwa 277-8561, Japan

(Received 27 November 2015 / Accepted 18 March 2016 / Published 17 May 2016)

Abstract

Feasibility of plasma current ramp-up in JT-60SA with no additional central solenoid (CS) flux consumption after the initial plasma formation has been investigated using an integrated modeling code suite (TOPICS). In our previous study, we developed a scenario in which the plasma current is ramped-up from 0.6 MA to 2.1 MA with no additional CS flux consumption by overdriving the plasma current using neutral beams (NB) and electron cyclotron (EC) waves. While the density profiles were prescribed in the previous study, in this study, we introduce a particle transport model according to the experimental results of JT-60U. It is shown that an internal transport barrier (ITB) can be obtained and the plasma current can be overdriven even if the particle transport is solved. The plasma current is ramped up in 330 s without CS flux consumption using 17 MW of NB and 3 MW of EC when the electron density is approximately 70% of the Greenwald limit. Although low-n ideal MHD modes are stable, an infinite-n ballooning mode is unstable in this scenario. The latter mode is presumably harmless, but to ensure the stability we investigate the pressure and the current profile controllability when the plasma current is overdriven. As a result, the infinite-n ballooning mode is shown to be stable when a broad pressure profile and a locally optimized magnetic shear are obtained using 2 MW of on-axis N-NB, 2 MW of off-axis N-NB, 4 MW of co-tangential P-NB and 7MW of EC with the electron density 30% of the Greenwald limit.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

plasma current overdrive, non-inductive, MHD stability, TOPICS, MARG2D, JT-60SA, simulation

DOI: 10.1585/pfr.11.2403068

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