UKAEA-CCFE-CP(19)33
Effect of fuel isotope mass on q-profile formation in JET hybrid plasmas
The initial Ohmic current ramp phase of JET hybrid plasmas, including a current ‘overshoot’ before the main heating, is used to optimise the q-profile shape to allow access to high β and avoid MHD instabilities [1]. Such hybrid plasmas have never been operated using tritium (T) or mixed deuterium-tritium (D-T) fuel. However, experiments with internal transport barriers (ITBs), which are also sensitive to the q-profile shape, were carried out in the 1997 JET D-T campaign [2]. It was found that the q-profiles produced in D-T experiments were slightly different to reference deuterium (D) plasmas, and modifications were needed to the heating power timing and waveform to obtain similar ITBs.