GLOBAL AND LOCAL CONDITIONS FOR THE L-H AND H-L TRANSITIONS ON JET

An analysis of the complete JET D-D threshold database, from 1990 to 1 997 inclusive is presented. A JET scaling is derived far the threshold power through the separatrix, estimated by considering also radiation losses from the bulk plasma. Such scalings are applied to obtain a fi rst qualitative estimate of the amount of power above threshold that i s needed to obtain steady-state high confinement (H89 > 1.8). The L-H and H-L transitions are also analysed in terms of local edge parameter s. The first results on isotope scaling of the H-mode power threshold in D-T and T-T plasmas are also presented, confirming the A(-1) scalin g.