INFRARED MEASUREMENTS OF THE DIVERTOR POWER AT JET

An infrared camera has been used to check the power balance calculatio ns in a series of JET divertor discharges. The discharges spanned the density range [n(e)] = (1-7) X 10(19) m-3, with the highest densities achieved by neutral beam heating and intensive gas puffing. For the di scharges in which IR data were taken, the total power to the target, a s deduced from the IR signal, was proportional to the expected diverto r target power estimated from P(in) - P(rad) - W, where P(in) is the i nput power to the plasma, P(rad) the measured radiated power, and W th e rate of change in the plasma stored energy. Close proportionality, p ointing 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 22 MW , of which up to 12 MW was monitored on the target as heat deposition by the IR system. Analysis of the data has shown no systematic trends of deteriorating power balance with increasing volume-averaged density or with heating power.