ASCOT modelling of ripple effects on toroidal torque

• Toroidal field ripple, delta=(B-max-B-min)/(B-max+B-min) in ITER will be relatively large, about 0.5% at the outer midplane. Due to the importance of toroidal rotation on plasma stability and confinement it is important to understand the consequences of a non-negligible ripple field on rotation. Guiding centre following Monte Carlo code ASCOT is used to evaluate the torque on plasma from co-current NBI in presence of toroidal magnetic field ripple. Simulations are made for a JET discharge from 2007 Ripple Campaign aimed to clarify the effect of ripple on fusion plasmas in preparation for ITER. ASCOT results show large reduction of torque from co-NBI and negative torque from thermal ions, which together could create a counter rotating edge plasma.

Nyckelord

MC

GC orbit following

ripple

torque

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