Role of the plasma shaping in ITB experiments on JET

A set of dedicated JET experiments is described where the plasma elongation (k) and triangularity (delta) were varied separately in order to study the influence of plasma magnetic topology on the internal transport barrier (ITB). With low delta, type III ELMs were observed and ITBs readily generated. At the highest delta, large type I ELMS and ELM free phases were observed but, at best, only marginal ITBs. At fixed delta the increase of the elongation of internal magnetic surface have a beneficial effect on the transport quality of the ITB.