Effects of neon seeding on high-performance deuterium JET-ITER baseline H-mode plasmas: experimental results and modelling

Future tokamak devices are required to operate with good fusion performance and sustainable power exhaust conditions. Impurity seeding has been demonstrated in various devices both to improve confinement and to facilitate power exhaust. The understanding of all the experimental observations is not yet complete. In this work, we present experimental data of a set of JET deuterium H-mode discharges in JET-ITER baseline configuration with increasing neon seeding and their integrated modelling using state-of-art transport models. We find that Ne increases the pedestal width. The pedestal top shows increased electron temperature Te and ion temperature Ti with increasing Ne, but decreased electron density ne. Overall, a remarkable increase in Te, Ti and pressure is observed throughout the plasma. The integrated modelling uses the JINTRAC and ASTRA codes with the TGLF-SAT2 turbulent transport model and NCLASS or FACIT for the neoclassical transport, in order to model a discharge with Ne seeding and its unseeded counterpart. The predictions show very good agreement with experimental data for both shots. The improved performance with Ne is found to come to large extent from the pedestal improvement, but a significant improvement due to turbulent transport reduction in the plasma core is also identified.