In:
Nuclear Fusion, IOP Publishing, Vol. 63, No. 2 ( 2023-02-01), p. 026011-
Abstract:
The formation of the radial electric field, E r in the scrape-off layer (SOL) has been experimentally studied for attached divertor conditions in stellarator W7-X. The main objective of this study is to test the validity in a complex three-dimensional (3D) island divertor of simple models, typically developed in tokamaks, relating E r in the SOL to the sheath potential drop gradient at the target. Additionally, we investigate the effect of the edge E r shear on the reduction of density fluctuation amplitude, a well-established phenomenon according to the existing bibliography. The main diagnostic for measurements in the SOL is a V-band Doppler reflectometer that can provide the measurement of the E r and density fluctuations with good spatial resolution. 3D measurements of divertor parameters have been carried out using infrared cameras, with the exponential decay length of the divertor heat flux ( λ q ) resulting in a suitable proxy for the model-relevant λ T , the exponential decay length of the temperature at the divertor. In the investigated attached regimes, it is shown for the first time that the formation of the E r in the SOL depends on parameters at the divertor, following a E r ∝ T e / λ q qualitatively similar to that found in a tokamak. Then, from the analyzed plasmas, the observed E r shear at the edge is linked to a moderate local reduction of the amplitude of density fluctuations.
Type of Medium:
Online Resource
ISSN:
0029-5515
,
1741-4326
DOI:
10.1088/1741-4326/aca6fa
Language:
Unknown
Publisher:
IOP Publishing
Publication Date:
2023
detail.hit.zdb_id:
2037980-8
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