Understanding of the Fundamental Differences in JET and JT-60U AT Discharges

Plasma current density simulations of JET and JT–60U shots in reverse–q advanced scenarios based on the previous data analysis of the identity plasma experiments have been performed. The effects of the main differences between the shots (neutral beam current density (jnbi), electron density and geometry) have been studied. The reversed q–profile (which was the target in this identity experiment is observed at the beginning of each shot) was sustained in JT–60U while it became flat in JET towards the end of shot.  In JET, jnbi is peaked on–axis whereas in JT–60U it is peaked off–axis (at r = 0.5) while NBI fraction of the selected shots is the same (22–24%). A strong density ITB appeared (at r = 0.5) in JT–60U but not in JET. The plasma geometry was mainly set to match but it was not identical. In addition, the extrapolation to JET steady–state operation has been done by testing the sensitivity of q to different externally driven currents, electron density and geometry in predictive current diffusion simulations. Moreover, critical bootstrap current density has been analysed.
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EFDP13065 1.96 Mb