Electromagnetic drift wave simulations of high performance discharges at JET

Hot ion H mode discharges at JET are analysed using interpretative and predictive transport simulation techniques. The simulations are based on a multifluid model for ion temperature gradient driven modes, collisionless trapped electron modes and impurity modes, including effects of electromagnetic perturbations and fast particle dilution in a simple model equilibrium. It is shown that the stabilizing effects of finite-beta electromagnetic perturbations are important for the simulations and allow for a unified description of bulk transport in L mode, H mode and hot ion H mode discharges at JET. In particular, it is shown that the ion heat diffusivity is substantially reduced for large values of beta away from the ideal threshold, which enables the simulations to reproduce the transient ELM-free phase of the pulses with ion temperatures reaching 15-25 keV.