Infra-Red Measurements of the Divertor Power at JET
An infrared camera has been used to check the power balance calculations in a series of JET divertor discharges. The discharges spanned the density range <ne> = 1-7x1019m-3, with the highest densities achieved by neutral beam heating and intensive gas puffing. For the discharges in which IR data were taken, the total power to the target, as deduced from the IR signal, was proportional to the expected divertor target power estimated from Pin-Prad-W, where Pin is the input power to the plasma, Prad- measured radiated power and W is the rate of change in the plasma stored energy. Close proportionality, pointing to good power balance, has been achieved in Ohmic plasmas, as well as in L- and H-modes with either RF and/ or NB heating up to 22MW, of which up to 12MW was monitored on the target as heat deposition by theIR system. Analysis of the data has shown no systematic trends of deteriorating power balance with increasing volume averaged density or with heating power.