Spontaneous improvements in particle and energy confinement have been observed in TJ-II plasmas with ≈300 kW of electron cyclotron resonance heating. Density and temperature profiles broaden giving rise to energy content enhancement up to a factor of 1.4. The transport analysis on one of these discharges describes the evolution of the profiles via a sudden reduction (∼50%) of the thermal and particle diffusivities inside the main plasma. A brief comparison with transition phenomena in other devices is given.
Energy confinement of beam-heated divertor and limiter discharges in Doublet III