Predictions of the impact of charge-exchange (CX) reactions on beam ions in the MAST Upgrade spherical tokamak have been compared to measurements carried out with a fission chamber (neutron fluxes) and a Fast Ion Deuterium-Alpha (FIDA) diagnostic. A simple model was developed to reconstruct the outer-midplane neutral density based on Thomson scattering data for the electron density and temperature, and on measurements of deuterium-alpha emission from edge neutrals. The main computational tools used in this study were the ASCOT orbit-following code and the FIDASIM code for producing synthetic FIDA signals.
The neutral density reconstructed using the simple model is found to qualitatively agree with SOLPS-ITER modelling and to yield a synthetic passive FIDA signal that is consistent with measurement. It was observed that when CX losses of beam ions are accounted for, predictions of neutron emission rates are more consistent with the measurements. It was also necessary to account for CX losses of beam ions in simulations to reproduce the measured passive FIDA signal. The results suggest that the neutral density reconstruction was a good approximation, that CX with edge neutrals causes significant beam-ion losses in MAST Upgrade, and that the ASCOT fast-ion CX model can be used to accurately predict the redistribution and loss of beam ions due to CX.