Impact of plasma density/collisionality on divertor heat flux width

Li, N. M.; Xu, X. Q.; Goldston, R. J.; Sun, J. Z.; Wang, D. Z.

doi:10.1088/1741-4326/abc839

Title: Impact of plasma density/collisionality on divertor heat flux width

Journal Article · Tue Dec 22 00:00:00 EST 2020 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/abc839· OSTI ID:1830500

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Dalian Univ. of Technology (China)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Princeton Univ., NJ (United States)

Both ASDEX-Upgrade (AUG) data and the generalized HD (GHD) model showed that the scrape-off width broadens as the density/collisionality increases [1, 2]. A series of BOUT++ transport simulations are performed to study the physics of the scaling characteristics of the divertor heat flux width vs density/collisionality via a plasma density scan with either fixed pressure profile or fixed temperature profile inside separatrix. Additionally, the simulations show that even in the drift dominated regime, the divertor heat flux width can be broadened due to the transition of the SOL residence time from the parallel particle flow time to the enhanced parallel conduction time as the collisionality/density increases as posited in the GHD model. In addition, the heat flux width is found to be proportional to the square root of ion mass for low collisionality while it has a weakly dependence on ion mass for high collisionality. Furthermore, our simulations show that as the density increases, the radial electric field (E_r) well shallows, which potentially weakens E_r × B flow shear stabilization of turbulence at high density.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); National Key Research and Development Program of China; China Postdoctoral Science Foundation; National Natural Science Foundation of China (NSFC)

Grant/Contract Number:: AC52-07NA27344; AC02-09CHII466; 2017YFE0301206; 2017YFE0300402; 2017YFE0301100; 2020M670740; 11675037

OSTI ID:: 1830500

Report Number(s):: LLNL-JRNL-812170; 1019348; TRN: US2216499

Journal Information:: Nuclear Fusion, Vol. 61, Issue 2; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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