Alpha particle-driven toroidal rotation in burning plasmas

Honda, Mitsuru; Takizuka, Tomonori; Tobita, Kenji; Matsunaga, Go; Fukuyama, Atsushi*

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are investigated. In DEMO plasmas, OFMC predicts that co-collisional torque and a counter torque always emerge regardless of the magnetic configuration, and both of them virtually cancel each other out. The gradient of the source profile of alpha particles produces both torques, and the magnitude of each torque is enhanced in the reversed shear configuration compared to the normal shear configuration, provided that the source gradient is finite and similar in both cases. The resultant rotation velocity estimated by TASK/TX is far below the threshold to stabilize resistive wall modes through intrinsic alpha-driven torque alone. It is estimated that neutral beam injection at a moderate power level may be necessary for obtaining toroidal rotation sufficient to stabilize resistive wall modes.