Beam absorption factor and absorbed torque after EAST NBI upgrade

The beam absorption factor and absorbed torque of neutral beam injection (NBI) have been investigated by using experimental measurements and NUBEAM/ONETWO/TRANSP modules after EAST NBI upgrade. In particular, the characteristics of prompt loss affecting the beam absorption factor are analyzed in depth. Simulations show that the beam absorption factor improves significantly when NBI is modified from counter-current to co-current, due to the great reduce of prompt loss. For co-current beams, the absorption factor increases with enlarging tangency radius and plasma density. Moreover, comparing the simulated neutron rate to neutron measurements in 0.5MA, MHD quiescent l-mode plasmas, the accuracy of beam absorption factor has been verified. In the end, based on simulation data, the absorbed torque due to NBI has also been analytical expressed by using multi-step fitting method (MFM). The absorbed torque studies are valuable for low-torque ITER-like physical researches on EAST.