Neutral Beam Injection (NBI) is a very flexible auxiliary heating method for tokamak plasmas, capable of being efficiently coupled to the various plasma configurations required in the Tritium and Deuterium–Tritium Experimental campaign (DTE2) to be undertaken in the JET device. In particular, experiments for high fusion yield and alpha particle studies require intense NBI heating, and for maximum performance and optimum fuel mixture control in Deuterium–Tritium (D–T) plasmas it is necessary to operate the JET NBI systems in both deuterium and tritium.
Technical aspects of the JET NBI systems for compatibility with T operation are discussed, and the associated commissioning is described. The characterisation of the JET NBI system in the tritium gas mode will be presented, with particular focus on the power and species mix measurements, this will be the first time that such data has been collected for Tritium neutral beams. Deuterium operation in the Tritium gas mode was successfully carried out in 2019 with no loss in reliability. In this period of operation the NBI power has been measured using beamline diagnostics and corroborated with plasma measurements. The species mix of the beam has been measured on the neutral beam test bed and also corroborated by plasma diagnostics on JET. These results will be presented alongside Tritium NBI results allowing comparison between the Deuterium and Tritium performance possible on JET NBI. Measurements of the NBI power in Tritium show that there will be a higher neutralised fraction than in Deuterium and a higher full energy fraction, this will lead overall to reduced beam penetration and lower particle flux per MW.