Impact of resonant magnetic perturbations on zonal modes, drift-wave turbulence and the L-H transition threshold

摘要

We study the effects of resonant magnetic perturbations (RMPs) on turbulence, flows and confinement in the framework of resistive drift-wave turbulence. This work was motivated, in parts, by experiments reported at the IAEA 2010 conference (Xu et al 2011 Nucl. Fusion 51 062030) which showed a decrease of long-range correlations during the application of RMPs. We derive and apply a zero-dimensional predator-prey model coupling the drift-wave-zonal-mode system (Leconte and Diamond 2012 Phys. Plasmas 19 055903) to the evolution of mean quantities. This model has both density-gradient drive and RMP amplitude as control parameters and predicts a novel type of transport bifurcation in the presence of RMPs. This model allows a description of the full L-H transition evolution with RMPs, including the mean sheared flow evolution. The key results are the following: (ⅰ) the L-I and I-H power thresholds both increase with RMP amplitude |b_x|, the relative increase of the L-I threshold scales as △P_(LI) α |b_x|2_(v_*)~(-2)ρ_s~(-2), where v_* is edge collisionality and ρ_s is the sound gyroradius. (ⅱ) RMPs are predicted to decrease the hysteresis between the forward and back-transition. (ⅲ) Taking into account the mean density evolution, the density profile-sustained by the particle source-has an increased turbulent diffusion compared with the reference case without RMPs which provides one possible explanation for the density pump-out effect.