Critical error fields for locked mode instability in tokamaks

摘要: Otherwise stable discharges can become nonlinearly unstable to disruptive locked modes when subjected a resonant m=2, n=1 error field from irregular poloidal coils, as in DIII‐D [Nucl. Fusion 31, 875 (1991)], or magnetic perturbation coils COMPASS‐C [Proceedings of the 18th European Conference on Controlled and Plasma Physics, Berlin (EPS, Petit‐Lancy, Switzerland, 1991), Vol. 15C, Part II, p. 61]. Experiments Ohmically heated deuterium with q≊3.5, n ≊ 2 × 1019 m−3 BT 1.2 T show that much larger relative (Br21/BT 1 10−3) is required produce mode small, rapidly rotating plasma (R0 = 0.56 m, f≊13 kHz) than medium‐sized plasmas 1.67 f≊1.6 kHz), where critical Br21/BT 10−4. This dependence threshold for instability explained by nonlinear tearing theory interaction perturbations p...