Development of JET hybrid scenario plasmas in deuterium and deuterium–tritium for impurity screening investigations

The low density and high temperature at the pedestal in hybrid scenarios on JET provide a unique test of the neo-classical screening in the periphery of the plasma that has previously been observed on JET in such plasmas. Hybrid scenario plasmas have been further developed to aid in the study of temperature gradient screening of high-Z impurities from the core of the plasma via plasma current, toroidal field, gas fuelling, density and isotope variations. The steps required to adapt the pulses from deuterium to deuterium–tritium are discussed and provide some guidance for future experiments that may operate in deuterium–tritium. The optimisation of the scenario allowed for improved bolometry data compared to the Deuterium Tritium Experiment 2 campaign on JET, hence this work provides vital evidence of impurity screening in a high fusion power, deuterium–tritium plasma.