Recent RF Experiments and Application of RF Waves to Real-Time Control of Safety Factor Profile in JT-60U

Journal Article · Mon Sep 26 00:00:00 EDT 2005 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.2098241· OSTI ID:20726327

Suzuki, T; Isayama, A; Ide, S; Fujita, T; Oikawa, T; Sakata, S; Sueoka, M; Hosoyama, H; Seki, M ^[1]

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1. Japan Atomic Energy Research Institute, Naka Fusion Research Establishment (Japan)

Two topics of applications of RF waves to current profile control in JT-60U are presented; application of lower-hybrid (LH) waves to safety factor profile control and electron cyclotron (EC) waves to neo-classical tearing mode (NTM) control. A real-time control system of safety factor (q) profile was developed. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location ({rho}CD) by controlling the parallel refractive index N parallel of LH waves through control of phase difference ({delta}{phi}) of LH waves between multi-junction launcher modules. The method for real-time q profile evaluation was newly developed, without time-consuming reconstruction of equilibrium, so that the method requires less computational time. Safety factor profile by the real-time calculation agrees well with that by equilibrium reconstruction with MSE. The control system controls {rho}CD through {delta}{phi} in such a way to decrease the largest residual between the real-time evaluated q profile q(r) and its reference profile qref(r). The real-time control system was applied to a positive shear plasma (q(0){approx}1). The reference q profile was set to monotonic positive shear profile having qref(0)=1.3. The real-time q profile approached to the qref(r) during application of real-time control, and was sustained for 3s, which was limited by the duration of the injected LH power. Temporal evolution of current profile was consistent with relaxation of inductive electric field induced by theoretical LH driven current. An m/n=3/2 NTM that appeared at {beta}N{approx}3 was completely stabilized by ECCD applied to a fully-developed NTM. Precise ECCD at NTM island was essential for the stabilization. ECCD that was applied to resonant rational surface (q=3/2) before an NTM onset suppressed appearance of NTM. In order to keep NTM intensity below a level, ECCD before the mode onset was more effective than that after mode saturation.

• OSTI ID: 20726327
• Journal Information: AIP Conference Proceedings, Vol. 787, Issue 1; Conference: 16. topical conference on radio frequency power in plasmas, Park City, UT (United States), 11-13 Apr 2005; Other Information: DOI: 10.1063/1.2098241; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CONTROL
CONTROL SYSTEMS
ECR CURRENT DRIVE
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTROMAGNETIC RADIATION
ELECTRONS
EQUILIBRIUM
EVALUATION
JT-60U TOKAMAK
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
MODE RATIONAL SURFACES
PLASMA
REAL TIME SYSTEMS
REFRACTIVE INDEX
RELAXATION
RF SYSTEMS
SHEAR
STARK EFFECT
TEARING INSTABILITY