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Author: David R Hatch
Requested Type: Poster
Submitted: 2018-03-01 10:23:17

Co-authors: M. K. Kotschenreuther, S. M. Mahajan, X. Liu, S. Saarelma, J. Hillesheim, C. Maggi, C. Giroud, and JET Contributors

Contact Info:
Univ of Texas, Austin
2515 Speedway, C1500
Austin, TX   78712
United States

Abstract Text:
Gyrokinetic simulations using the GENE code are presented, which target a fundamental understanding of JET pedestal transport and, in particular, its modification after installation of an ITER like wall (ILW). A representative pre-ILW (carbon wall) discharge is analyzed as a base case. In this discharge, magnetic diagnostics identify washboard modes, which preferentially affect the temperature pedestal and have frequencies (accounting for Doppler shift) consistent with microtearing modes. Linear gyrokinetic simulations identify microtearing modes with scale lengths and frequencies comparable to magnetic fluctuation data. A similar ILW discharge is examined, which recovers a similar value of H98, albeit at reduced pedestal temperature. This discharge is distinguished by a much higher value of eta, which produces strong ion temperature gradient (ITG) and electron temperature gradient (ETG) driven instabilities in gyrokinetic simulations. Global simulations indicate that ITG turbulence produces substantial heat flux and very little particle flux. Sensitivity tests varying the density gradient demonstrate an ITG particle pinch that balances diffusion, suggesting that ITG may mediate the density profile. Additional fundamental aspects of pedestal transport and shear suppression will also be discussed.