Abstract:
The high confinement mode (H-mode) is a spontaneously occurring regime of improved thermal confinement in magnetic fusion energy experiments, and is planned to be the fundamental operating mode of the ITER burning plasma experiments. Recent experimental work points towards the key role that turbulent driven shear flows, denoted as zonal flows, play in triggering the transition into H-mode. In this talk, we discuss the first experimental studies of the key physics mechanism thought to occur in the transition. In particular, the nonlinear kinetic energy transfer between shear flows and the ambient turbulence is investigated in the EAST tokamak during the L-H transition. Our results show that as the rate of energy transfer from the turbulence into the shear flow becomes comparable to the energy input rate into the turbulence, the turbulence amplitude collapses and the transition into the H-mode occurs. The results agree qualitatively with a reduced numerical model of the physics, and point out the way to direct numerical simulations of the L-H transition.
Continuing our careers theme for the quarter, this plasma seminar will include a discussion of career steps