Recent progress toward high performance above the Greenwald density limit in impurity seeded discharges in limiter and divertor tokamaks

An overview is given of recent advances toward the realization of high dens ity, high confinement plasmas with radiating mantles in limiter and diverto r tokamaks worldwide. Radiatively improved mode discharges on the Torus Exp eriment for Technology Oriented Research 94 (TEXTOR-94) [Proceedings of the 16th IEEE Symposium on Fusion Engineering, 1995 (Institute for Electrical and Electronics Engineers, Piscataway, NJ, 1995), p. 470] have recently bee n obtained at trans-Greenwald densities (up to (n) over bar /n(GW)=1.4) wit h high confinement mode free of edge localized modes (ELM-free H-mode) conf inement quality. Experiments in DIII-D [J. Luxon, Proceedings of the 11th I AEA Conference on Plasma Physics and Controlled Nuclear Fusion Research (In ternational Atomic Energy Association, Vienna, 1987), Vol. 1, p. 159] diver tor plasmas with a low confinement mode edge have confirmed the dramatic ch anges in confinement observed with impurity seeding on TEXTOR-94. Recent ex periment with impurity seeding on the Joint European Torus [Rebut , Fusion Eng. Des. 22, 7 (1993)], and the Japanese Atomic Energy Research Institute Tokamak 60 Upgrade [Horiike , Fusion Eng. Des. 16, 285 (1991); Hosogane , P roceedings of the 16th IAEA Conference on Plasma Physics and Controlled Nuc lear Fusion Research Montreal, 1987 (International Atomic Energy Associatio n, Vienna, 1987), Vol. 3, p. 555] have extended high confinement in ELMy H- mode plasmas to higher densities. Finally, recent progress in the physical understanding of radiating mantle plasmas is summarized. (C) 2001 American Institute of Physics.