Error field mode studies on JET, COMPASS-D and DIII-D, and implications for ITER

摘要

New experiments on JET, COMPASS-D and DIII--D have identified the critical scalings of error field sensitivity and harmonic content effects, enabling predictions to be made of the require- ments for larger devices such as ITER. Thresholds are lowest at low density, a regime proposed or H mode access on ITER. Results suggest a moderate error field sensitivity (δB/B ≈ 10~(-4)) for ITER, comparable with the size of its intrinsic error, although there are uncertainties in scaling behaviour. Other studies on COMPASS-D and DIII-D show that sideband harmonics to the (2, 1) component play an important role. Thus, a correction system for ITER will be important, with flexibility to correct sidebands desirable, possibly assisted by beam rotation. Such a system has been designed and is capable of reducing multiple harmonic error levels to ～2 × 10~(-5).