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.
- Publication Date:
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- 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. https://doi.org/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. https://doi.org/10.1088/1741-4326/ab2af9. https://www.osti.gov/servlets/purl/1558759.
@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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Figure 1: Pressure balance in the SOL, plotted along flux surfaces (plotted versus Z, the normal cylindrical coordinate height coordinate, at each point on the flux surface). The top figure shows the ratio of upstream total pressure to target total pressure, and the bottom figure shows the same but withmore »
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Figures / Tables found in this record:
Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.