A numerical study of neutral beam injection into spheromaks ispresented. The beam evolution is calculated through a Monte-Carlosimulation and the plasma MHD equilibrium is determinedself-consistently with the current produced by the beam. The exactequations of motion are used for the beam particles instead of the usualguiding-centre approximation. The guiding-centre trajectories areclearly different from the actual particle trajectories and thisdifference produces discrepancies in the total driven current and in thecurrent profiles. A reduction of the plasma effective charge, Zeff,does not result in an improvement in the current drive efficiencybecause the reduction of the stopping cross section is compensated by anincrease in the electron cancelling current. The safety factor profile ofthe self-consistent equilibria shows a clear sensitivity to the drivencurrent profile. The value at the magnetic axis (q0) diminishes whenthe beam is injected at the magnetic axis and increases for injectionabove the axis. Power deposition profiles for simple injectionconfigurations are also shown.
Stability analysis of TJ-II stellarator NBI driven Alfvén eigenmodes in ECRH and ECCD experiments