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 density, high confinement plasmas with radiating mantles in limiter and divertor tokamaks worldwide. Radiatively improved mode discharges on the Torus Experiment 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 been obtained at trans-Greenwald densities (up to n̄/n_GW= 1.4) with high confinement mode free of edge localized modes (ELM-free H-mode) confinement quality. Experiments in DIII-D [J. Luxon et al., Proceedings of the 11th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Association, Vienna, 1987), Vol. 1, p. 159] divertor plasmas with a low confinement mode edge have confirmed the dramatic changes in confinement observed with impurity seeding on TEXTOR-94. Recent experiment with impurity seeding on the Joint European Torus [Rebut et al., Fusion Eng. Des. 22, 7 (1993)], and the Japanese Atomic Energy Research Institute Tokamak 60 Upgrade [Horiike et al., Fusion Eng. Des. 16, 285 (1991); Hosogane et al., Proceedings of the 16th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research Montreal, 1987 (International Atomic Energy Association, 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.