Neutron emission Doppler-shift measurements in deuterium–tritium plasmas

Spectrometry of the neutron emission is discussed as a probe of the fuel ion velocity distribution in tokamak plasmas where the instrumental energy calibration allows determination of Doppler shifts on an absolute scale or relative to the emission of thermal plasma conditions. Such Doppler shifts have been measured for plasmas of different heating methods at the Joint European Torus (JET) using a neutron spectrometer of the magnetic proton recoil (MPR) type. The principles of the MPR spectrometer as a rotation diagnostic are discussed together with the results obtained for the JET plasmas. The development potential of neutron spectrometry as a rotation diagnostic at the accuracy level of ±1 km/s for toroidal and poloidal rotation is projected, especially, for use on burning plasma tokamaks.