Suppressing Locked Magnetic Island with Wave-driven Currents

The use of localized electron cylcotron current drive has been studied extensively as a means to control and mitigate magnetic islands in tokamaks. The use of static field perturbations to align locked neoclassical tearing modes with wave-driven currents has been demonstrated in DIII-D (F.A. Volpe et al., Phys. Rev. Letters 115, 175002, 2015), and sensitivity of tearing mode suppression to wave injection alignment has been shown numerically (D. De Lazzari, E. Westerhof, Nucl. Fusion 49, 075002, 2009). We introduce a static perturbation to a cylindrical or axisymmetric toroidal field, and investigate the effect of wave injection alignment and width on the suppression of a resonant magnetic island using a simple numerical model. We consider the impact of these parameters on the effectiveness of wave-driven currents in stabilizing the growth of locked modes. Predictions are given in parameter ranges relevant to DIII-D and ITER.