(IT/P1-6) Characteristics of the H-mode Pedestal in Improved Confinement Scenarios in ASDEX Upgrade, DIII-D, JET and JT-60U

C.F. Maggi1), R.G. Groebner2), N. Oyama3), R. Sartori4), L.D. Horton1), A.C.C. Sips1), W. Suttrop1), ASDEX Upgrade Team1), T. Leonard2), T.C. Luce2), M.R. Wade2), DIII-D Team2), Y. Kamada3), H. Urano3), JT-60U Team3), Y. Andrew5), C. Giroud5), E. Joffrin6), E. de la Luna7), EFDA JET Contributors, Pedestal and Edge Physics Steady State Operation Topical Groups of ITPA
1) Max Planck Institut für Plasmaphysik, Garching, Germany
2) General Atomics, San Diego, California, USA
3) Japan Atomic Energy Agency,Japan
4) EFDA Close Support Unit, Garching, Germany
5) UKAEA, Abingdon, UK
6) CEA, Cadarache, France
7) CIEMAT, Madrid, Spain

Abstract.  Pedestal and global plasma parameters are compared in ELMy H-mode discharges from ASDEX Upgrade (AUG), DIII-D, JET and JT-60U with varying input power and current profiles. Both electron and ion pedestal pressures are studied. The increase in pedestal pressure (pPED) with power is continuous, reflecting the continuous transition from standard H-mode to improved confinement scenario. Higher pPED than in standard H-modes are found in improved H-modes in AUG and in JT-60U high betapol H-modes at q95=6.5. In AUG improved H-modes pPED increases with power due to an increase of both pedestal top density and temperature. In DIII-D pPED increases primarily due to an increase of pedestal temperature, through an increase in width of the Te ETB and an increase of both width and gradient of the Ti ETB. For AUG the confinement improvement at high power is due in part to increased core stored energy and in part to increased pedestal stored energy, while in DIII-D hybrid discharges it is due to increased core confinement. In JT-60U high betapol H-modes at q95=6.5 and high delta the improved confinement is due to an increase of WPED, while in reversed shear H-modes to an increase in Wcore. In JET hybrid discharges at 1.4 MA Wth increases with power and deltadue to an increase of WPED. In all four tokamaks improved edge stability is correlated to increasing total betapol and H98(y,2) increases with pedestal betapol.

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