PPPL-5386
Overview of NSTX Upgrade Initial Results and Modelling Highlights
Authors: J.E. Menard, D.J. Battaglia, R.E. Bell, E.
Belova, M.D. Boyer, A. Diallo, F. Ebrahimi, N. Ferraro, E.
Fredrickson, S. Gerhardt, N. Gorelenkov, W. Guttenfelder, S.M.
Kaye, B.P. LeBlanc, R. Lunsford, D. Mueller, C.E. Myers, M.
Ono, J.-K. Park, M. Podesta, Y. Ren, C.H. Skinner, T.
Stoltzfus-Dueck, Z. Wang, R. Andre, N. Bertelli, A. Bhattacharjee,
D. Boyle, C.S. Chang, D. Darrow, L. Delgado-Aparicio, S. Ethier,
D. Gates,J. Hosea, S. Jardin, M.A. Jaworski, E. Kolemen, S.
Ku, R. Maingi, R. Perkins, F. Poli, B. Stratton, G. Taylor, W.
Wang, and S.J. Zweben
Abstract: The National Spherical Torus Experiment (NSTX) has
undergone a major upgrade, and the NSTX Upgrade (NSTX-U) Project was
completed in the summer of 2015. NSTX-U first plasma was
subsequently achieved, diagnostic and control systems have been
commissioned, H-Mode accessed, magnetic error fields identified and
mitigated, and the first physics research campaign carried out.
During 10 run weeks of operation, NSTX-U surpassed NSTX-record
pulse-durations and toroidal fields, and high-performance ~1MA
H-mode plasmas comparable to the best of NSTX have been sustained
near and slightly above the n=1 no-wall stability limit and with
H-mode confinement multiplier H98y,2 above 1. Transport and
turbulence studies in L-mode plasmas have identified the coexistence
of at least two iongyroscale turbulent micro-instabilities near the
same radial location but propagating in opposite (i.e. ion and
electron diamagnetic) directions. These modes have the
characteristics of ion-temperature gradient and micro-tearing modes,
respectively, and the role of these modes in contributing to thermal
transport is under active investigation. The new second more
tangential neutral beam injection was observed to significantly
modify the stability of two types of Alfven Eigenmodes. Improvements
in offline disruption forecasting were made in the areas of
identification of rotating MHD modes and other macroscopic
instabilities using the
Disruption Event Characterization and Forecasting (DECAF) code.
Lastly, the Materials Analysis and Particle Probe (MAPP) was
utilized on NSTX-U for the first time and enabled assessments of the
correlation between boronized wall conditions and plasma
performance.These and other highlights from the first run campaign
of NSTX-U are described.