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The aim of this paper is to report on recent advances made in global gyrokinetic simulations of ion temperature gradient (ITG) modes and other microinstabilities. The nonlinear development and saturation of ITG modes and the role of E × B zonal flows are studied with a global nonlinear δf formulation that retains parallel nonlinearity and thus allows for a check of the energy conservation property as a means of verifying the quality of the numerical simulation. Due to an optimized loading technique, the conservation property is satisfied with an unprecedented quality well into the nonlinear stage. The zonal component of the perturbation evolves to a quasi-steady state with regions of ITG suppression, strongly reduced radial energy flux and steepened effective temperature profiles alternating with regions of higher ITG mode amplitudes, larger radial energy flux and flattened effective temperature profiles. A semi-Lagrangian approach free of statistical noise is proposed as an alternative to the nonlinear δf formulation. An ASDEX-Upgrade experiment with an internal transport barrier is analysed with a global gyrokinetic code that includes trapped electron dynamics. The weakly destabilizing effect of trapped electron dynamics on ITG modes in an axisymmetric bumpy configuration modelling W7-X is shown in global linear simulations that retain the full electron dynamics. Finite β effects on microinstabilities are investigated with a linear global spectral electromagnetic gyrokinetic formulation. The radial global structure of electromagnetic modes shows a resonant behaviour with rational q values.

Present experiments with ion-cyclotron heating are mainly devoted to study ion-cyclotron resonance heating of hydrogen and 3He in a deuterium plasma. However, for a thermonuclear fusion experiment this frequency range has the undesirable feature of turning into ?-particle heating as soon as alpha particles are created. Because of the large Doppler broadening of their resonance, a significant amount of power is then absorbed in the outer part of the plasma. To avoid this drawback, the use of second-harmonic minority heating of hydrogen or 3He is suggested. Second-harmonic heating of 3He in a deuterium plasma can also be used to study fusion and ?-particle confinement without creating a large neutron flux. The absorption for these scenarios is found to be strong as long as mode conversion occurs between the fast magneto-acoustic wave and the ion Bernstein wave. The propagation of the fast wave and its interaction with the ion Bernstein wave have been calculated with a finite-element code in plane geometry.

The wave induced fluxes of energetic trapped ions during ICRF heating of tokamak plasmas are calculated by using quasi-linear equations. A simple single particle model of this transport mechanism is also given. Both a convective flux proportional to kø|E+|2and a diffusive flux proportional to are found. Here, køis the toroidal wavenumber and E+is the left hand polarized wave field. The convective flux may become significant for large køif the wave spectrum is asymmetric in kø. But for kø??1, a condition satisfied in most previous and planned experiments, radial transport driven directly by the ICRF wave is unimportant.