EDGE MEASUREMENTS IN JET DURING THE L-H MODE TRANSITION

Measurements of flux and electron temperature across the divertor region in JET have been made using Langmuir probes mounted in the target tile surfaces, a reciprocating probe in the scrape-off layer, and CCD camera observations. It is found that flux density radial profiles steepen in going from L to H mode, and this is observed as a fall in flux and D-alpha light along a chord at large radii. Fluxes integrated across the strike zone region of the tiles only exhibit a transient fall, however, and then an exponential rise back to the L-mode value. From these measurements particle confinement times in L and H mode have been calculated, they rise from typically 0.15 in the L-mode to 0.8 s in the H-mode. Calculations of the sputtering of the divertor target tiles show little difference between the two modes.