UW-CPTC 11-15R4 Resonant-magnetic-perturbation-induced plasma transport in H-mode pedestals

Plasma toroidal rotation reduces reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational (q = m/n) magnetic flux surfaces. Hence, it causes radial perturbations δBρm/n to be small there, and thus inhibits magnetic island formation and stochasticity in the edge of high (H-) mode confinement tokamak plasmas. However, electron collisional damping combined with the spatial magnetic flutter δBρm/n induced by RMPs in the vicinity of rational surfaces causes a radial electron heat diffusivity χ e ∼ (1/2) ∑ m,n[δB̂ρm/n(x)/B0] 2 χ e‖ (x) in which χ eff e‖ ∼ (v 2 Te/νe)/(1 + x /δ ‖) is an effective parallel electron thermal diffusivity. These effects are reduced by magnetic shear effects at a distance x from rational surfaces for |x| > δ‖ but amplified for δB̂ρm/n(x) > δB̂ρm/n(0). A kinetic, toroidal model of these RMPflutter-induced plasma transport effects is developed and compared to a previously developed cylindrical model. The RMP-induced increases in plasma transport can be large enough to reduce plasma gradients in H-mode pedestals. Thus, they may contribute to suppressing edge localized modes in tokamak plasmas.