EFDA-JET-CP(05)02/24

Analysis of Electron Internal Transport Barriers in JET Low and Reversed Shear Discharges

The study of electron thermal transport and electron Internal Transport Barriers (eITBs) in regimes with dominant electron heating is of great importance for ITER. Single JET pulses with eITB were studied in [1,2]. In this paper for the first time a consistent study of 15 predominantly electron heated JET pulses with and without eITB is presented, covering the full range of safety factor (q) profiles, from strongly reversed shear (s) via low shear to standard positive shear. The difference in q profiles is mainly brought about by the use of various Lower Hybrid (LH) power levels. The presence of eITBs in the experiments is analyzed in two ways. First, local reduction of electron thermal diffusion is searched for by means of local power balance analysis, performed with the CRONOS code [3]. CRONOS is also used to calculate the current driven by LH, which is an essential ingredient to calculate q. For many pulses no or very limited Motional Stark Effect data (from which q is derived) are present; when MSE data are available, they will be compared with the CRONOS calculations.
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