Error Field Experiments on JET and COMPASS-D, and Implications for ITER
Abstract
Error field driven modes remain a significant concern for ITER, with the potential to cause serious disruptions. New approaches on COMPASS-D and JET, using Ohmic ITER-like plasmas, testing sideband harmonic effects, the key scaling dependencies, and performing similarity experiments, enabling a self-consistent approach to cross-machine scaling models for error field tolerances. These confirm a scaling towards a low tolerance of intrinsic error (δ B/B ~ 10-4-10-5) for ITER. Experimentally, thresholds are low at low density, a regime necessary for access to H-mode on ITER. COMPASS-D results show strong scaling with toroidal field and q, consistent with JET experiments. This suggests a very low threshold for ITER, although further experiments are in progress to confirm this scaling. Comparisons are also made with various theoretical models. Sideband harmonic studies demonstrate a strong `drag' effect of (3,1) harmonics on (2,1) penetration thresholds. Thus the correction system capable of allowing independently for sidebands, which is presently being designed, will be essential for ITER, preferably assisted by neutral beam induced rotation.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1997
- Bibcode:
- 1997APS..DPPdMP128B