Passive Burn Control in a Tokamak Plasma Using Toroidal Field Ripple

The feasibility of passive burn control method using toroidal field ripple-degraded alpha-particle confinement with free expansion of the major radius has been confirmed by a 1.5-dimensional transport code. In this transport code, a scaling of the ripple loss of alpha particles derived from the results of an orbit-following Monte Carlo code is used. For passive burn control, however, >5% of the major radius margin is necessary and the resulting ripple-induced power loss of alpha particles exceeds 20%. Passive burn control in combination with feedback control of the field ripple, a hybrid burn control method, demonstrates very effective burn temperature control. In hybrid burn control, the necessary major radius margin and the controlled field ripple are only 2 to 3% and δ_c ≲ 1%, respectively. The resulting total power loss of alpha particles is <15%.