Overview of experiments with radiation cooling at high confinement and high density in limited and diverted discharges

An overview is presented of recent experiments with radiating mantles on li miter and divertor machines, realizing simultaneously high confinement and high density at high-radiation levels. A variety of operational regimes has been observed and the characteristics of each are documented. High-perform ance plasmas (i.e. edge localized mode (ELM)-free H-mode confinement qualit y f(H93) greater than or equal to 1 and normalized beta values beta(n) grea ter than or equal to 2 simultaneously) with radiating mantles have been dem onstrated under quasistationary conditions during the maximum flattop time of the machine (equal to tens of confinement times) on DIII-D and TEXTOR-94 . Maximum values for beta(n) up to 4 and for the advanced tokamak confineme nt-stability product beta(n) x f(L89) up to 13, have been obtained in very high confinement mode (VH-mode) like discharges with radiating mantles in D III-D. There is a striking similarity between improved ohmic confinement di scharges (with or without Ne seeding) and radiating mantle discharges, indi cating a possible common origin for the confinement improvement observed. P ossible scenarios for the application of radiating mantles on larger machin es such as JET and JT-60U are indicated.