Pedestal Confinement in Hybrid Versus Baseline Plasmas in JET

The hybrid confinement regime has been extensively explored in the 2008-2009 JET campaigns, obtaining confinement factors up to HIPB98(y,2)~1.4 and normalised pressure bN~3 in both low and high triangularity configurations. A comparison of pedestal and core confinement has been recently carried out in ASDEX Upgrade and DIII-D]. The present paper examines the contribution of the pedestal to the total confinement in the hybrid regime in JET. The pedestal parameters are measured using the new High Resolution Thomson Scattering (HRTS) data (measuring electron temperature Te and density ne) combined with Charge Exchange data (measuring the ion temperature Ti, the effective charge Zeff). Ion density is estimated from ne and Zeff assuming carbon as main impurity: ni = ne(7-Zeff)/6. To investigate the origin of the better confinement in the hybrids, a comparison with baseline H-mode scenarios is made. In total, four different scenarios are studied, see table 1 for details.
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