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

A fast-scanning Langmuir probe and an array of divertor Langmuir probe s are used to characterize the cross-field heat transport (chi(perpend icular to) and to compare plasma conditions ''upstream'' along a magne tic flux tube to conditions at the divertor. Three distinct regimes ar e found which depend on the power into the SOL and the edge plasma den sity: (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 alon g 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 div ertor strike points. The scaling between regimes (1) and (2) can be de scribed by a transport model that includes anomalous cross-field heat transport (0.25 < chi(perpendicular to) < 0.5 m(2) s(-1)), sheath cond uction, and classical parallel electron conduction.