Simulations of combined neutral beam injection and ion cyclotron heating with the TORIC-SSFPQL package

A source describing the injection of fast ions due to the ionization of high-energy neutral beams has been added to the surface-averaged quasilinear Fokker-Planck code SSFPQL (Brambilla 1994 Nucl. Fusion 34 1121). For this purpose, the multiple-beam NBI code SINBAD(Feng et al 1995 Comput. Phys. Commun. 88 161) has been included as a module in SSFPQL, with the modifications required to handle arbitrary axisymmetric equilibria. Alternatively, the neutral beam injection (NBI) source can be built using the output of a Monte Carlo NBI code. We have also added a term describing losses of fast ions during thermalization, and a subroutine evaluating the neutron production rate by nuclear reactions. With these extensions, iterations between SSFPQL and the full-wave solver TORIC (Brambilla 1999 Plasma Phys. Control. Fusion 41 1) can now be used to investigate the strong interplay between NBI and ion cyclotron (IC) heating. By comparing the predicted and measured neutron production rates from D-D reactions in a discharge with combined NBI and IC heating in ASDEX Upgrade we obtain a plausible estimate of the importance of fast-ion losses (FILs), even if their cause cannot be identified. We find, however, that the plasma composition, in particular the presence of low Z impurities, plays a more critical role than FILs in limiting the efficiency of this heating scheme.