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-β 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 β 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.