This paper describes a series of experiments undertaken in 1999 that werespecifically designed to elucidate the roles of elongation and triangularityon the confinement in the steady-state ELMy H-mode regime. The new results arediscussed in the context of results from earlier experiments on JET and otherdiverted tokamaks where the role of triangularity has been investigated. Thebehaviour of the H-mode transport barrier (the pedestal) and the confinementare presented in some detail for the new experiments. The picture whichemerges from the data is complex and not described entirely satisfactorily bycurrent global scaling models. The implications for ITER-FEAT are explored andfound to be favourable and some possible avenues for future experiments on JETare described.
Loss of confinement due to reduction of the edge pedestal in JET