CHARACTERISTICS OF DIVERTOR PLASMA AND SCRAPE-OFF LAYER IN JT-60U

Heat flux to the divertor is measured by thermography and the heat transport in the scrape-off layer is studied in beam heated discharges of JT-60U. The heat flux onto the divertor is approximately 50% of total beam power at maximum. The in-out asymmetry of the heat flux P(HEAT)in/P(HEAT)out is as large as 20-40% when the ion grad-B drift is toward the divertor. Differences in P(HEAT)in/P(HEAT)out due to the direction of ion grad-B drift are as large as approximately 40%. A scaling of the peaking factor Y of heat flux, defined by Y = 2piRfq(max)/P(HEAT), is obtained for beam heated discharges in JT-60U with a wide range of plasma parameters. The Y corresponds to the inverse of the thickness of the scrape-off layer. From a statistical analysis, it is found that the peaking factor Y of heat flux scales as P(HEAT)0.49 +/- 0.18n(e)BAR-0.45 +/- 0.22q(eff)-0.67 +/- 0.18.