Calculation of Neutral Beam Injected Torque and Its Effective Tangency Major Radius for EAST

Toroidal rotation has been recognized to have significant effects on the transport and magnetohydrodynamic (MHD) stability of tokamak plasmas. Neutral beam injection (NBI) is the most effective rotation generation method on current tokamak devices. To estimate the effective injected torque of the first neutral beam injection system on EAST, a simplified analytic method was derived. Calculated beam torque values were validated by those obtained from the NUBEAM code simulation. According to the results, for the collisional torque, the effective tangential radius for torque deposition is close to the beam tangency major radius. However, due to the dielectric property of tokamak plasma, the equivalent tangency major radius of the J × B torque is equal to the average major radius of the magnetic flux surface. The results will be useful for the research of toroidal momentum confinement and the experimental analysis of momentum transport related with NBI on EAST.