MHD in the Spherical Tokamak
21 st IAEA Fusion Energy Conference, Chengdu, China, 2006 MHD in the Spherical Tokamak MAST authors: SD Pinches , I Chapman, MP Gryaznevich, DF Howell, SE Sharapov, RJ Akers, LC Appel, RJ Buttery, NJ Conway, G Cunningham, TC Hender, GTA Huysmans, EX/7-2Ra R Martin and the MAST and NBI Teams NSTX authors: A.C. Sontag, S.A. Sabbagh, W. Zhu, J.E. Menard, R.E. Bell, J.M. Bialek, M.G. Bell, D.A. Gates, A.H. Glasser, B.P. Leblanc, F.M. Levinton, K.C. Shaing, D. Stutman, K.L. Tritz, H. Yu, and the NSTX Research Team EX/7-2Rb Office of Supported by Science This work was jointly funded by the UK Engineering & Physical Sciences Research Council and Euratom MHD physics understanding to reduce performance risks in ITER and a CTF – Error field studies – RWM stability in high beta plasmas – Effects of rotation upon sawteeth – Alfvén cascades in reversed shear EX/7-2Ra EX/7-2Rb Error field studies in MAST EX/7-2Ra Error fields: slow rotation, induce instabilities, terminate discharge Mega Ampere Spherical Tokamak R = 0.85m, R/a ~ 1.3 Four ex-vessel (ITER-like) error field correction coils wired to produce odd-n spectrum, Imax = 15 kA·turns (3 turns) Locked mode scaling in MAST EX/7-2Ra Error fields contribute to βN limit: n=1 kink B21 is the m = 2, n = 1 field component normal to q = 2 surface: • Similar density scaling observed on NSTX • Extrapolating to a Spherical Tokamak Power Plant / Component Test Facility gives locked mode thresholds ≈ intrinsic error ⇒ prudent to include EFCCs [Howell et al .
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