Alpha particle-driven toroidal rotation in burning plasmas

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

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, an orbit-following Monte Carlo code OFMC predicts that the profile of a collisional torque is influenced near the magnetic axis by a reversed magnetic shear configuration, while that of a torque is not. It is found that the gradient of the source profile of alpha particles produces the co-directed collisional torque and a counter-directed torque, and both torques virtually cancel each other out in the central region of the plasma. A non-negligible torque shear and resulting toroidal rotation in the co-direction are obtained in a weakly reversed-shear configuration, but the estimated rotation velocity is below the threshold to stabilize resistive-wall modes through intrinsic alpha-driven torque alone.