The separatrix electron density in JET, ASDEX upgrade and alcator C-Mod H-mode plasmas: A common evaluation procedure and correlation with engineering parameters

The separatrix electron density in JET, ASDEX upgrade and alcator C-Mod H-mode plasmas: A common evaluation procedure and correlation with engineering parameters

The separatrix electron density is an important parameter for core-edge scenario integration in tokamak devices, as it influences plasma confinement, divertor detachment and disruption avoidance. This quantity has been measured in H-mode discharges on JET, ASDEX Upgrade and Alcator C-Mod by applying...

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Main Authors: D. Silvagni, O. Grover, A. Stagni, J.W. Hughes, M.A. Miller, B. Lomanowski, G. Ciraolo, M. Dunne, T. Eich, L. Frassinetti, C. Giroud, I. Jepu, A. Kallenbach, A. Kirjasuo, A. Kuang, T. Luda, C. Perez von Thun, T. Pütterich, H.J. Sun, H. Zohm
Format: Article
Language:English
Published: Elsevier 2025-03-01
Series:Nuclear Materials and Energy
Subjects:
Tokamak
Separatrix
Neutral pressure
Electron density
Scrape-off layer
Divertor
Online Access:http://www.sciencedirect.com/science/article/pii/S2352179125000079
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Summary:The separatrix electron density is an important parameter for core-edge scenario integration in tokamak devices, as it influences plasma confinement, divertor detachment and disruption avoidance. This quantity has been measured in H-mode discharges on JET, ASDEX Upgrade and Alcator C-Mod by applying the same fitting function to Thomson scattering measurements, and by employing the same analysis technique based on scrape-off layer power balance. To estimate the power crossing the separatrix, the inter-ELM time derivative of the plasma energy dW/dt has been experimentally evaluated and found to be approximately a constant fraction of the absorbed heating power. Correlations between ne,sep and engineering parameters have been investigated, revealing that ne,sep scales with the divertor neutral pressure p0,div in a similar manner across all devices. Additionally, when ne,sep is normalized to the obtained p0,div dependency, no clear correlation with the plasma current is found. These observations are in agreement with the 2-point model, which suggests that the upstream separatrix density is mainly set by the recycling at the divertor target.
ISSN:2352-1791

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