Collector probe analysis of tungsten transport to the far-SOL from the DIII-D SAS-VW divertor experiment

Messer, Seth H.; Mateja, Jeremy D.; Nichols, Jacob H.; Cacheris, Alec; Duran, Jonah D.; Zamperini, Shawn A.; Sinclair, Gregory; Donovan, David; Abrams, Tyler; Odstrcil, Tomas; Ren, Jun; Garcia, W.; Unterberg, Ezekial A.; Stangeby, Peter C.; Rudakov, Dmitry L.; Elder, John D.; Watkins, J.

doi:10.1016/j.nme.2023.101566

Title: Collector probe analysis of tungsten transport to the far-SOL from the DIII-D SAS-VW divertor experiment

Journal Article · 06 December 2023 · Nuclear Materials and Energy

DOI: https://doi.org/10.1016/j.nme.2023.101566 · OSTI ID:2229171

Messer, Seth H. ^[1];

^[1];

^[2]; Cacheris, Alec ^[1];

^[2];

^[3];

^[3]; Donovan, David ^[1]; Abrams, Tyler ^[3]; Odstrcil, Tomas ^[3];

^[1]; Garcia, W. ^[4];

^[2];

^[5]; Rudakov, Dmitry L. ^[6];

^[5]; Watkins, J. ^[4]

Univ. of Tennessee, Knoxville, TN (United States)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
General Atomics, San Diego, CA (United States)
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Univ. of Toronto, ON (Canada)
Univ. of California, San Diego, CA (United States)

Experimental results from the 2022 tungsten (W)-coated Small Angle Slot (SAS-VW) divertor campaign at DIII-D coupled with interpretive 3DLIM modelling show opposing trends for core impurity content when compared to impurity deposition on far-Scrape Off Layer (SOL) Collector Probes (CPs) with increasing main ion density. SAS-VW is a closed, W-coated divertor designed to more easily facilitate divertor detachment while reducing impurity leakage. An experiment performed a series of upper-single-null L-mode discharges in each toroidal magnetic field (B_T) direction, with increasing main ion density (line-averaged density = 3.15–4.35e19 m^–3) that approaches and slightly exceeds the divertor detachment threshold. The results indicate: a) increased radial W transport with decreasing peak $$T^{LP}_{e,t}$$; and b) negligible change in W content in the far-SOL at the outer mid-plane with the onset of divertor detachment. Preliminary W deposition measurements using double-sided, graphite CPs inserted at the Midplane Materials Evaluation System (MiMES) reveal a 75% decrease over the density scan when operating in the unfavorable (ion B×∇B out of the divertor) B_T direction. In contrast, soft X-ray (SXR) radiation from the same discharges is used as a proxy for W core contamination, showing core W content that increases by 77% with increasing line-averaged density. Similar L-mode discharges conducted in the favorable B_T direction result in significantly less deposition on CPs. Using an interpretive modeling workflow following Zamperini 2022 for assessing the transport of W sputtered from the SAS-VW divertor, the analysis suggests that W migration to the main chamber surfaces during the campaign may also contribute to far-SOL deposition.

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Research Organization:: General Atomics, San Diego, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: AC05-00OR22725; FC02-04ER54698; FG02-07ER54917; NA0003525; SC0019256; SC0023378

OSTI ID:: 2229171

Journal Information:: Nuclear Materials and Energy, Journal Name: Nuclear Materials and Energy Vol. 38; ISSN 2352-1791

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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