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P: Fachverband Plasmaphysik
P 5: Poster Session 1
P 5.1: Poster
Montag, 9. März 2020, 16:30–18:30, Empore Lichthof
Statistical analysis of confinement data from pellet fuelled high-density plasmas in ASDEX Upgrade — •Tobias Engelhardt1,2, Otto Kardaun2, Peter Lang2, Martin Prechtl1, and Asdex Upgrade Team2 — 1Hochschule Coburg — 2Max-Planck-Institut für Plasmapysik
A dataset of pellet-fuelled discharges in the high density regime of ASDEX Upgrade (AUG) has been collected, covering 8 years of operation. It comprises scenarios with moderate performance, as well as attempts to achieve high performance by applying either N-seeding or high shaping. This data shows that the H06 scaling, see [1], is more appropriate to describe plasma confinement in this regime, than the H98(y,2) scaling. Additionally, the enhanced confinement gained by the different methods cannot be maintained when the density ne exceeds the Greenwald density nGw. Confidence bands, obtained from statistical analysis confirm this feature.
According to observations at JET (with carbon wall), see [2], higher H-factors (H98(y,2)) at constant ne/nGw were observed when the triangularity δ was increased. Whether this trend is also present at AUG (with tungsten first wall), will be investigated. The reduced confinement when exceeding nGw can possibly be attributed to a rising separatrix density ne,sep. The approximation that primarily the divertor density n0Div influences ne,sep, see [3], is somewhat simplified. Therefore, potential other correlations between ne,sep and other plasma physical parameters will be analysed.
[1] J. Johner, FST 59 (2010) 308 [2] V. Mukhovatov et al., PPCF 45 (2003) A235 [3] A. Kallenbach et al., PPCF 60 (2018) 308