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

Abstract

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.

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1]; ORCiD logo [1];  [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1558759
Grant/Contract Number:  
AC02-05CH11231; AC02-09CH11466; FC02-04ER54698
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 9; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; scrape-off layer; tokamak; gyrokinetic; simulation

Citation Formats

Churchill, R. M., Chang, C. S., Ku, S., Hager, R., Maingi, R., Stotler, D. P., and Qin, H. Pressure balance in a lower collisionality, attached tokamak scrape-off layer. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab2af9.
Churchill, R. M., Chang, C. S., Ku, S., Hager, R., Maingi, R., Stotler, D. P., & Qin, H. Pressure balance in a lower collisionality, attached tokamak scrape-off layer. United States. doi:10.1088/1741-4326/ab2af9.
Churchill, R. M., Chang, C. S., Ku, S., Hager, R., Maingi, R., Stotler, D. P., and Qin, H. Fri . "Pressure balance in a lower collisionality, attached tokamak scrape-off layer". United States. doi:10.1088/1741-4326/ab2af9.
@article{osti_1558759,
title = {Pressure balance in a lower collisionality, attached tokamak scrape-off layer},
author = {Churchill, R. M. and Chang, C. S. and Ku, S. and Hager, R. and Maingi, R. and Stotler, D. P. and Qin, H.},
abstractNote = {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.},
doi = {10.1088/1741-4326/ab2af9},
journal = {Nuclear Fusion},
number = 9,
volume = 59,
place = {United States},
year = {2019},
month = {7}
}

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