ITER-EDA PHYSICS DESIGN REQUIREMENTS AND PLASMA PERFORMANCE ASSESSMENTS

Physics design guidelines,plasma performance estimates, and sensitivit y of performance to changes in physics assumptions are presented for t he ITER-EDA Interim Design. The overall ITER device parameters have be en derived from the performance goals using physics guidelines based o n the physics R&D results. The ITER-EDA design has a single-null diver tor configuration (divertor at the bottom) with a nominal plasma curre nt of 21 MA, magnetic field of 5.68 T, major and minor radius of 8.14 m and 2.8 m, and a plasma elongation (at the 95% flux surface) of simi lar to 1.6 that produces a nominal fusion power of similar to 1.5 GW f or an ignited burn pulse length of greater than or equal to 1000 s. Th e assessments have shown that-ignition at 1.5 GW of fusion power can b e sustained in ITER for 1000 s given present extrapolations of H-mode confinement (tau(E) = 0.85 x tau(ITER93H)), helium exhaust (tau(He)/< tau)(E) = 10), representative plasma impurities (n(Be)/n(e) = 2%), and beta limit [beta(N) = beta(%)/(I/aB) less than or equal to 2.5]. The provision of 100 MW of auxiliary power, necessary to access to H-mode during the approach to ignition, provides for the possibility of drive n burn operations at Q = 25. This enables ITER to fulfill its mission of fusion power (similar to 1-1.5 GW) and fluence (similar to 1 MWa/m( 2)) goals if confinement, impurity levels, or operational (density, be ta) limits prove to be less favorable than present projections. The po wer threshold for H-L transition, confinement uncertainties, and opera tional limits (Greenwald density limit and beta limit) are potential p erformance limiting issues. Improvement of the helium exhaust (tau(He )/tau(E) less than or equal to 5) and potential operation in reverse-s hear mode significantly improve ITER performance.