Reactor-relevant quiescent H-mode operation using torque from non-axisymmetric, non-resonant magnetic fields

Results from recent experiments demonstrate that quiescent H-mode (QH-mode) sustained by magnetic torque from non-axisymmetric magnetic fields is a promising operating mode for future burning plasmas. Using magnetic torque from n = 3 fields to replace counter-I_p torque from neutral beam injection (NBI), we have achieved long duration, counter-rotating QH-mode operation with NBI torque ranging from counter-I_p to up to co-I_p values of 1-1.3 Nm. This co-I_p torque is 3 to 4 times the scaled torque that ITER will have. These experiments utilized an ITER-relevant lower single-null plasma shape and were done with ITER-relevant values of ν_ped ^* and β_N^ped. These discharges exhibited confinement quality H_98y2 = 1. 3, in the range required for ITER. In preliminary experiments using n = 3 fields only from a coil outside the toroidal coil, QH-mode plasmas with low q₉₅ = 3.4 have reached fusion gain values of G = β_N H₈₉/q₉₅ ² = 0.4, which is the desired value for ITER. Shots with the same coil configuration also operated with net zero NBI torque. The limits on G and co-I_p torque have not yet been established for this coil configuration. QH-mode work to has made significant contact with theory. The importance of edge rotational shear is consistent with peeling-ballooning mode theory. Qualitative and quantitative agreements with the predicted neoclassical toroidal viscosity torque is seen.