Gyrokinetic theory and simulations on ion heat transport physics in helical systems have recently been developed. Damping processes of zonal flows driven by ion temperature gradient (ITG) turbulence in helical systems have been analytically investigated based on the gyrokinetic theory as a generalization of the previous work by Rosenbluth and Hinton for tokamaks. A collisionless response function of the zonal flow to given source terms is derived by taking account of the helical geometry and finite-orbit-width effects. Validity of the analytical predictions are verified by the Eulerian gyrokinetic code (GKV code) with very-high resolution of the phase space. The GKV simulation extended to take account of helical-ripple-trapped particles is also applied to the ITG turbulence in helical systems. The ITG turbulent transport level in a model case for the inward-shifted magnetic-axis configuration with a stronger instability drive is effectively suppressed by the zonal flow, and is reduced to a level comparable to that in the less unstable case for the standard configuration with smaller side-band helical field components.

Plasma turbulence driven by the ion temperature gradient (ITG) is theoretically studied with high-resolution Eulerian kinetic simulations. A spectral analysis of the velocity distribution function in the slab ITG turbulence clarifies how the entropy variable associated with the fine-scale structure of the distribution function is produced by the turbulent heat transport in the presence of the temperature gradient, transferred from macro to microscales in the velocity space through phase-mixing processes, and dissipated by collisions. The entropy spectral function is analytically derived and confirmed by the simulation result. It is shown that the entropy spectrum obeys a power law in the range that is free from instability sources and collisional dissipation. The Eulerian gyrokinetic simulation of the toroidal ITG turbulence yields the ion thermal diffusivity in the steady turbulent state, in which the balance between the entropy production by the ion thermal transport and the collisional dissipation is verified. A formula for a long time behavior of the zonal flow potential in helical systems is analytically derived, by which collisionless zonal flow dynamics in tokamaks and helical plasmas are compared. A good agreement between the formula and the gyrokinetic simulation results is obtained.

A compact toroid (CT) plasmoid injection is considered to be one of the most promising schemes for central fueling of a fusion device. However, there is the possibility that the device magnetic field leaking to the gun region (the leakage magnetic field) prevents the CT from entering the fusion device. By using magnetohydrodynamic (MHD) numerical simulations, we investigate three-dimensional dynamics of an accelerated CT in a cylindrical conductor and examine the effect of the leakage magnetic field on the CT penetration.