Pressure balance in a lower collisionality, attached tokamak scrapeoff layer
Abstract
Previously the gyrokinetic neoclassical code XGCa found that the pressure balance (or momentum balance) in the diverted scrapeoff 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 gyrocenterfluid pressure balance equation allows identifying from the XGCa code results which physical processes dominate the setting of pressure variation in the scrapeoff layer. This pressure balance equation is applied to the simulation of a DIIID Hmode 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:

 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Publication Date:
 Research Org.:
 Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
 Sponsoring Org.:
 USDOE Office of Science (SC), Fusion Energy Sciences (FES)
 OSTI Identifier:
 1558759
 Grant/Contract Number:
 AC0205CH11231; AC0209CH11466; FC0204ER54698
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Nuclear Fusion
 Additional Journal Information:
 Journal Volume: 59; Journal Issue: 9; Journal ID: ISSN 00295515
 Publisher:
 IOP Science
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; scrapeoff 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 scrapeoff layer. United States: N. p., 2019.
Web. doi:10.1088/17414326/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 scrapeoff layer. United States. https://doi.org/10.1088/17414326/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 scrapeoff layer". United States. https://doi.org/10.1088/17414326/ab2af9. https://www.osti.gov/servlets/purl/1558759.
@article{osti_1558759,
title = {Pressure balance in a lower collisionality, attached tokamak scrapeoff 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 scrapeoff 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 gyrocenterfluid pressure balance equation allows identifying from the XGCa code results which physical processes dominate the setting of pressure variation in the scrapeoff layer. This pressure balance equation is applied to the simulation of a DIIID Hmode 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 = {10.1088/17414326/ab2af9},
journal = {Nuclear Fusion},
number = 9,
volume = 59,
place = {United States},
year = {2019},
month = {7}
}
Web of Science
Figures / Tables:
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Figures / Tables found in this record: