A global gyrokinetic toroidal full-f five-dimensional Vlasov simulation GT5D (Idomura et al 2008 Comput. Phys. Commun. 179 391)is extended including sources and collisions. Long time tokamak micro-turbulence simulations in open system tokamak plasmas are enabled for the first time based on a full-f gyrokinetic approach with self-consistent evolutions of turbulent transport and equilibrium profiles. The neoclassical physics is implemented using the linear Fokker-Planck collision operator, and the equilibrium radial electric field E r is determined self-consistently by evolving equilibrium profiles. In ion temperature gradient driven turbulence simulations in a normal shear tokamak with on-axis heating, key features of ion turbulent transport are clarified. It is found that stiff ion temperature T i profiles are sustained with globally constant L ti ≡ |T i /T i | near a critical value, and a significant part of the heat flux is carried by avalanches with 1/f type spectra, which suggest a self-organized criticality. The E r shear strongly affects the directions of avalanche propagation and the momentum flux. Non-diffusive momentum transport due to the E r shear stress is observed and a non-zero (intrinsic) toroidal rotation is formed without momentum input near the axis.

A global gyrokinetic toroidal particle code for a 3D nonlinear simulation (GT3D) has been developed to study the ion temperature gradient driven-trapped electron mode (ITG-TEM) turbulence in reactor relevant tokamak parameters [1]. In GT3D, gyrokinetic ions and drift-kinetic (trapped) electrons are solved using a finite-element PIC method. The code uses a new δf method based on a canonical Maxwellian distribution F CM (P φ ,ε,µ), which is

The behaviour of runaway electrons in three types of magnetic turbulence in tokamak discharges is reviewed: (a) micromagnetic turbulence, (b) low-m/n magnetic islands in a sea of stochasticity, (c) macroscale magnetic turbulence. The confinement of runaway electrons is much better than that of bulk thermal electrons in (a) and (b), but is greatly degraded in (c). Spontaneous and intrinsic termination of runaway current, which will be favourable for tokamak fusion reactors in order to reduce the heat flux on the first wall, was first found in JT-60U by decreasing the safety factor at the plasma surface qs to around 2 or 3 by three different methods: (i) controlled inward plasma shift, (ii) a vertical displacement event, (iii) plasma current rampup.

The operation conditions to avoid runaway electron generation at the major disruption have been investigated in JT-60U tokamak plasmas. It has been found that runaway electrons are not observed for low Bt of ⩽ 2.2 T or low plasma current quench rates (Iγ ≡ -(dIp/dt)/Ip) of <50 s-1. Furthermore, they are not observed for low effective safety factors defined at the plasma edge (qeff) of ⩽ 2.5 even for high Iγ of 300-400 s-1, which is the case for uncontrolled disruptions accompanied by large plasma displacements (e.g., vertical displacement events (VDEs)). On the other hand, in controlled disruptions with small plasma shifts, qeff easily increases above 8, and runaway electrons are observed even for low current quench rates of 50-100 s-1. Furthermore, it has been found that in these position controlled disruptions the runaway current tail can rapidly decay even for zero or weakly positive plasma surface voltages. These observations of the avoidance and termination of runaway electrons suggest an anomalous loss mechanism for runaway electrons.

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