ITER-EDA Physics Design Requirements and Plasma Performance Assessments

Abstract

Physics design guidelines, plasma performance estimates, and sensitivity of performance to changes in physics assumptions are presented for the ITER-EDA Interim Design. The overall ITER device parameters have been derived from the performance goals using physics guidelines based on the physics R&D results. The ITER-EDA design has a single-null divertor configuration (divertor at the bottom) with a nominal plasma current 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 {approximately}1.6 that produces a nominal fusion power of {approximately}1.5 GW for an ignited burn pulse length of {ge}1000 s. The assessments have shown that ignition at 1.5 GW of fusion power can be sustained in ITER for 1000 s given present extrapolations of H-mode confinement ({tau}{sub E} = 0.85 {times} {tau}{sub ITER93H}), helium exhaust ({tau}*{sub He}/{tau}{sub E} = 10), representative plasma impurities (n{sub Be}/n{sub e} = 2%), and beta limit [{beta}{sub N} = {beta}(%)/(I/aB) {le} 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 driven burn operations at Q = 15. This enables ITER to fulfill its mission of fusion power ({approximately} 1--1.5 GW) and fluence ({approximately}1 MWa/m{sup 2}) goals if confinement, impurity levels, or operational (density, beta) limits prove to be less favorable than present projections. The power threshold for H-L transition, confinement uncertainties, and operational limits (Greenwald density limit and beta limit) are potential performance limiting issues. Improvement of the helium exhaust ({tau}*{sub He}/{tau}{sub E} {le} 5) and potential operation in reverse-shear mode significantly improve ITER performance.