Theoretical Evaluations of Neutral Beam Injection Efficiency for the TJ-II Helical-Axis Stellarator

Theoretical evaluations of neutral beam injection (NBI) efficiency for the TJ-II helical-axis stellarator have been done for several expected scenarios using the FASOLT code, an adaptation of the FAFNER three-dimensional NBI Monte Carlo code to the peculiar geometry, vacuum vessel, and helical indented magnetic surfaces of TJ-II. The code is used in combination with another one-dimensional flux coordinates transport code (PLASMATOR). Results for 1-MW injected power, comparing coinjection and counterinjection, as well as 2- and 4-MW balanced injection, are discussed with emphasis on fast ion losses and wall loads. Some preliminary results, including radial electric field effects, are also presented.