SCALING OF PLASMA PARAMETERS IN THE SOL AND DIVERTOR FOR ALCATOR C-MOD

A fast-scanning Langmuir probe and an array of divertor Langmuir probes are used to characterize the cross-field heat transport (chi(perpendicular to) and to compare plasma conditions ''upstream'' along a magnetic flux tube to conditions at the divertor. Three distinct regimes are found which depend on the power into the SOL and the edge plasma density: (1) a sheath-limited conduction regime where the divertor target temperature and density is similar to the values upstream, (2) a high-recycling regime where plasma pressure is approximately constant along field lines while n(e) is high and T-e is low at the divertor, and (3) a detached divertor regime where n(e) and T-e collapse near the divertor strike points. The scaling between regimes (1) and (2) can be described by a transport model that includes anomalous cross-field heat transport (0.25 < chi(perpendicular to) < 0.5 m(2) s(-1)), sheath conduction, and classical parallel electron conduction.