Pressure balance in a lower collisionality, attached tokamak scrape-off layer

Churchill, R. M.; Chang, C. S.; Ku, S.; Hager, R.; Maingi, R.; Stotler, D. P.; Qin, H.

doi:10.1088/1741-4326/ab2af9

Title: Pressure balance in a lower collisionality, attached tokamak scrape-off layer

Journal Article · Fri Jul 12 00:00:00 EDT 2019 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ab2af9· OSTI ID:1558759

^[1]; Chang, C. S. ^[1]; Ku, S. ^[1]; Hager, R. ^[1]; Maingi, R. ^[1];

^[1]; Qin, H. ^[1]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Previously the gyrokinetic neoclassical code XGCa found that the pressure balance (or momentum balance) in the diverted scrape-off layer (SOL) does not follow that from the fluid description based on the Chew–Goldberger–Low (CGL) theory. In this paper a gyrocenter parallel momentum moment equation is derived for pressure balance (or momentum balance) in a tokamak SOL, for use in interpreting this difference. The new gyrocenter-fluid pressure balance equation allows identifying from the XGCa code results which physical processes dominate the setting of pressure variation in the scrape-off layer. This pressure balance equation is applied to the simulation of a DIII-D H-mode discharge, with a lower ion collisionality in the SOL, and the Coulomb and atomic collisions are not strong enough to yield a detached divertor plasma. It is found that the total pressure balance is much better matched using the gyrocenter parallel momentum moment equation. Electrons are shown to be dominantly adiabatic, while ions have multiple contributions to pressure balance, including terms originating from particle drifts. Furthermore, these results show that in strong gradient, low collisionality regions of the SOL, the typical fluid reductions miss important effects captured in the gyrokinetic model.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: AC02-05CH11231; AC02-09CH11466; FC02-04ER54698

OSTI ID:: 1558759

Journal Information:: Nuclear Fusion, Vol. 59, Issue 9; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
scrape-off layer
tokamak
gyrokinetic
simulation

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