In situ calibration of neutral beam port-through power and estimation of neutral beam deposition on LHD

The neutral beam (NB) shine-through profile is routinely monitored on the L arge Helical Device (LHD) both to calibrate the port-through power of the N B and to evaluate the NB-deposition power to LHD plasmas. The profile is me asured with a calorimeter (CM) array on an armor plate of the NB counter wa ll inside the LHD vacuum vessel. An infrared camera is also used to check t he beam profile where CMs are not located, and measures a temperature incre ase of the armor plate due to the NB heat load. The measured beam profile i s compared to the calculated NB profile at the armor plate. The measurement indicates that the beam is not uniform at the exit of the ion source and t hat the steering angle of the beam in the horizontal direction is not the s ame as the designed value. It is found that the monitoring of the NB shine- through profile is important to estimate the NB port-through power and the NB deposition power, especially when the neutral beam injector (NBI) is bas ed on a large negative-hydrogen ion source. (C) 2001 American Institute of Physics.