Dependence of divertor turbulence on plasma density and current in TCV

Wüthrich, Curdin; Theiler, C.; Oliveira, D. S.; Wang, Y.; Ducker, R.; Durr-Legoupil-Nicoud, G.; Duval, B. P.; Galassi, D.; Golfinopolus, T.; Lee, K.; Offeddu, N.; Tsui, C. K.

doi:10.1088/1741-4326/ad8df1

Dependence of divertor turbulence on plasma density and current in TCV

Journal Article · Mon Nov 18 00:00:00 EST 2024 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ad8df1· OSTI ID:2584548

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Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

To reliably predict the distribution of heat and particle fluxes at the target plates of tokamaks, a comprehensive understanding of turbulence throughout the entire Scrape-Off-Layer (SOL) is imperative. This study examines divertor turbulence systematically across a broad parameter range on the TCV tokamak, including variations in magnetic field direction, plasma current I_p ∈ [140,320] kA, edge safety factor q₉₅ ∈ [2.6,4.7] and Greenwald fraction f_G ∈ [0.18,0.6]. The TCV X-point Gas Puff Imaging (GPI) system is used to measure 2D filament properties in the inner and outer divertor region. The fluctuation levels in the divertor are found to strongly increase with density (to 80% over most of the SOL) while remaining insensitive to I_p. The previously identified divertor-localized filaments (DLF), located on the bad curvature side of the outer divertor leg, are found to be a common feature on TCV, while no filaments are observed in the PFR. DLFs are present over most of the parameter space and in both field directions. However, they are absent, or appear only closer to the target, for sufficiently large Λ_div ≳ 10 or q₉₅ ≳ 3.7. Across both I_p and f_G scans, some clear trends with Λ_div are found for divertor filament sizes and velocities, and with target fall-off lengths of density and heat flux profiles at the outer target. This study provides important experimental insights to turbulent transport in the divertor also for comparison with self-consistent, turbulence simulations and extrapolation to future reactor conditions.

View Accepted Manuscript (DOE)

Research Organization:: Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: NA0003525

OSTI ID:: 2584548

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 1 Vol. 65; ISSN 0029-5515; ISSN 1741-4326

Publisher:: IOP Science - IAEACopyright Statement

Country of Publication:: United States

Language:: English

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