Atomic processes relevant to neutral beam based tokamak diagnostics

Charge exchange and beam emission spectroscopy in magnetic confinement fusion plasmas are reviewed. The range of spectral phenomenology is illustrated from the JET tokamak using fast deuterium and helium beams. The helium observations are new. The atomic reactions concerned in the emission and their interplays are summarised. The state of cross‐section data for the analysis is briefly assessed.