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Operational limits for density and beta play a key role in determining whether The International Thermonuclear Experimental Reactor (ITER) can meet its goal of about 1 MW/m{2} neutron flux onto the first wall. This goal corresponds to roughly 1500 MW of fusion power and is equivalent to <beta> = 0.032. Given the optimum temperature <T> = 10 keV for achieving ignition power blance, a line-average density of n = n(mean) = 1.5n(GR) is required, where n(GR) = I(p)/pia{2} denotes the empirical Greenwald limit. Recent experiments have obtained steady state edge localized mode (ELM)ing H modes with line average densities exceeding the Greenwald limit, thereby documenting that the limit is empirical, not fundamental. Models for the occurrence of a density limit are discussed. Even though they are safely below the ideal magnetohydrodynamic (MHD) beta limits, long pulse ITER-like tokamak discharges exhibit beta limits arising from spontaneously generated magnetic island structures, which have been interpreted as arising from neoclassical bootstrap current. Prospects for eddy current heating (ECH) stabilization of these islands appear favourable, theoretically.

Additional information

Authors: PERKINS F W ET AL, ITER Joint Central Team, San Diego (US);BORRASS K ET AL, IPP, Garching (DE);CAMPBELL D ET AL, JET Joint Undertaking, Abingdon, Oxon (GB);GREENWALD M J, Plasma Fusion Center, MIT, Cambridge (US);HENDER T C ET AL, AEA Fusion, Culham Laboratory, Abingdon (GB);KAMADA Y ET AL, JAERI, Ibaraki-ken (JP);LAHAYE R ET AL, General Atomics, San Diego (US)
Bibliographic Reference: Article: 16th IAEA Fusion Energy Conference, Montreal (CA), October 7-11, 1996
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