STABILITY OF A RADIATIVE MANTLE IN ITER

We report results of a study to evaluate the efficacy of various impur ities for heat dispersal by a radiative mantle and radiative divertor (including SOL). We have derived a stability criterion for the mantle radiation which favors low Z impurities and low ratios of edge to core thermal conductivities. Since on the other hand the relative strength of boundary line radiation to core bremsstrahlung favors high Z impur ities, we find that for the ITER physics phase argon is the best gaseo us impurity for mantle radiation. For the engineering phase of ITER, m ore detailed analysis is needed to select between krypton and argon.