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Abstract

A simplified analysis is given of the problem of estimating the 'epistemic probability' for ITER to attain a power amplification factor Q larger than a certain lower bound. Attention is restricted to the parameters of ITER-FEAT and the 1998 ITER design. The probabilistic framework is briefly discussed and the distributional interval estimates for Q following from the interval estimates of the confinement time are derived (a) for ITER operation at constant fusion output power P-fus, and (b) for operation at a temperature that maximizes Q = P-fus/P-aux. The second situation requires a radial integration of the flux surface averaged energy balance. Instead of a local transport model, a simple class of temperature profiles is used. The results are represented graphically. A generalization of the widely used fusion triple product plot against temperature is suggested. The analysis presupposes that at the reference operating point in situation (a), and in the range of operating temperatures projected to be achievable in situation (b), the conditions for reaching standard ELMy H mode in ITER are met. The practical conclusion of the article is that under this premise ITER-FEAT has a fairly large epistemic probability of obtaining plasma conditions with prevalent alpha particle heating.