COREDIV simulations of D and D-T high current-high power Baseline pulses in JET-ITER Like Wall

The two best performing pulses of the so called ITER-Baseline scenario (Ip=3.5 MA and Pin≈ 35 MW) of JET ILW, one in deuterium (D) the other in deuterium-tritium (D-T) plasma are examined and compared in this study. Generally, the D-T Baseline pulses exhibit an electron density level higher than the D pulses and the plasma energy is higher than in the comparable D pulses by up to 20%, reaching about 12 MJ in the pulse studied here. In contrast with the D pulses, the D-T pulses are often characterized by the increase in time of the radiated power in the mantle region, which may lead to the loss of the ELM activity when the threshold H-L transition power is approached and to the subsequent plasma disruption due to excessive radiation. In this study we try to identify the physical mechanisms responsible for this behaviour using the available experimental data (principally the total radiated power from the bolometry) and the results of the steady state fluid COREDIV model (1-D in the core, 2-D in the SOL), self-consistent with respect to core-SOL and to main plasma-impurities. The electron density and temperature profiles are numerically reconstructed as well as the radiated power density profiles, indicating no major difference in impurity transport in D and D T. In fact, the impurity transport coefficients used in COREDIV to match the experimental radiated power profiles are similar in the two pulses. The computed tungsten sources and densities are lower in the D-T pulse and the divertor impurity retention capability is a little better in the D-T pulse, indicating a stronger collisional drag force in the SOL. The higher electron density and the broadening of its profile are the main cause of the observed increase of the radiated power in the D-T pulse.