The orbit averaged particle source from neutral beam injection in tokamaks

Methods are developed for evaluation of the drift orbit averaged particle source, (S), in realistic neutral beam injection scenarios. Finite Larmor radius (FLR) and finite orbit width effects are included providing an accurate treatment of beam injection geometries in both standard and spherical tokamaks. With the knowledge of (S) the full beam distribution is readily obtained using well-known Fokker-Planck modelling schemes in constant of motion variables. For the considered ITER beam injection scenarios the analysis provides distributions which are in good agreement with equivalent distributions calculated by the TRANSP analysis code. The inclusion of FLR effects is important for fusion devices with relatively small values of the magnetic field; this is illustrated by considering the beam injection scenario of a spherical tokamak.