Particle and energy fluxes observed in the scrape-off layer of JFT-2 tokamak

Particle and energy fluxes in the scrape-off layer produced by poloidal limiters are studied in the JFT-2 tokamak with mean electron densities of 1.3 × 10 13 and 2.8 × 10 13 cm −3 . The measurements were made by a combined Langmuir/thermoprobe and an infrared camera. The electron density in the scrape-off layer decays exponentially with increasing minor radius, implying that the cross-field diffusion is of the order of the Bohm diffusion. It is shown that heat transmission to the limiter more than 1 cm behind the edge radius is determined by a sheath of Maxwellian particles. Near the edge radius, accelerated electrons play a major role, which is indicated by toroidal anisotropy of the heat flux in the lower-density case.