The edge parameters of electron cyclotron resonance heated plasmas inthe TJ-II stellarator are reported. Data from atomic beam diagnostics andelectrical probes have been used for edge and scrape-off layercharacterization. Scans in heating power and plasma density for H and Heplasmas have been performed, for a given magnetic configuration. A linearincrease of the diffusion coefficient at the last-closed magnetic surfacewith the ratio of injected power to plasma density and a similar valueof that parameter for the two atomic species investigated were obtained.Global particle confinement times between 3 and 15 ms have been deduced, andtransition to an enhanced confinement mode in H plasmas has been observedunder some conditions. The role of high-energy particle losses, due totrapping into the relatively high magnetic ripple, in the global energybalance of TJ-II plasmas is addressed.
Density behaviour and particle losses in RF discharge plasmas of the URAGAN-3M torsatron