U.S. Department of EnergyOffice of Scientific and Technical Information
Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors
Abstract
The Alcator C-Mod team has recently developed a feedback system to measure and control surface heat flux in real-time. The system uses real-time measurements of surface heat flux from surface thermocouples and a pulse-width modulated piezo valve to inject low-Z impurities (typically N2) into the private flux region. It has been used in C-Mod to mitigate peak surface heat fluxes >40 MW/m2 down to <10 MW/m2 while maintaining excellent core confinement, H98>1. While the system works quite well under relatively steady conditions, use of it during transients has revealed important limitations on feedback control of impurity seeding in conventional vertical target plate divertors. In some cases, the system is unable to avoid plasma reattachment to the divertor plate or the formation of a confinement-damaging x-point MARFE. This is due to the small operational window for mitigated heat flux in the parameters of incident plasma heat flux, plasma density, and impurity density as well as the relatively slow response of the impurity gas injection system compared to plasma transients. Given the severe consequences for failure of such a system to operate reliably in a reactor, there is substantial risk that the conventional vertical target plate divertor will not provide an adequatelymore »
- Authors:
- Publication Date:
- DOE Contract Number:
- FC02-99ER54512
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
- OSTI Identifier:
- 1880126
- DOI:
- https://doi.org/10.7910/DVN/YZJOCX
Citation Formats
Brunner, D., Wolfe, S. M., LaBombard, B., Kuang, A. Q., Lipschultz, B., Reinke, M. L., Hubbard, A., Hughes, J., Mumgaard, R. T., Terry, J. L., Umansky, M. V., and Alcator C-Mod Team. Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors. United States: N. p., 2018.
Web. doi:10.7910/DVN/YZJOCX.
Brunner, D., Wolfe, S. M., LaBombard, B., Kuang, A. Q., Lipschultz, B., Reinke, M. L., Hubbard, A., Hughes, J., Mumgaard, R. T., Terry, J. L., Umansky, M. V., & Alcator C-Mod Team. Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors. United States. doi:https://doi.org/10.7910/DVN/YZJOCX
Brunner, D., Wolfe, S. M., LaBombard, B., Kuang, A. Q., Lipschultz, B., Reinke, M. L., Hubbard, A., Hughes, J., Mumgaard, R. T., Terry, J. L., Umansky, M. V., and Alcator C-Mod Team. 2018.
"Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors". United States. doi:https://doi.org/10.7910/DVN/YZJOCX. https://www.osti.gov/servlets/purl/1880126. Pub date:Tue Oct 16 00:00:00 EDT 2018
@article{osti_1880126,
title = {Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors},
author = {Brunner, D. and Wolfe, S. M. and LaBombard, B. and Kuang, A. Q. and Lipschultz, B. and Reinke, M. L. and Hubbard, A. and Hughes, J. and Mumgaard, R. T. and Terry, J. L. and Umansky, M. V. and Alcator C-Mod Team},
abstractNote = {The Alcator C-Mod team has recently developed a feedback system to measure and control surface heat flux in real-time. The system uses real-time measurements of surface heat flux from surface thermocouples and a pulse-width modulated piezo valve to inject low-Z impurities (typically N2) into the private flux region. It has been used in C-Mod to mitigate peak surface heat fluxes >40 MW/m2 down to <10 MW/m2 while maintaining excellent core confinement, H98>1. While the system works quite well under relatively steady conditions, use of it during transients has revealed important limitations on feedback control of impurity seeding in conventional vertical target plate divertors. In some cases, the system is unable to avoid plasma reattachment to the divertor plate or the formation of a confinement-damaging x-point MARFE. This is due to the small operational window for mitigated heat flux in the parameters of incident plasma heat flux, plasma density, and impurity density as well as the relatively slow response of the impurity gas injection system compared to plasma transients. Given the severe consequences for failure of such a system to operate reliably in a reactor, there is substantial risk that the conventional vertical target plate divertor will not provide an adequately controllable system in reactor-class devices. These considerations motivate the need to develop passively stable, highly compliant divertor configurations and experimental facilities that can test such possible solutions.},
doi = {10.7910/DVN/YZJOCX},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {10}
}
Works referencing / citing this record:
Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high- Z vertical target plate divertor: performance, limitations and implications for fusion power reactors
journal, July 2017
- Brunner, D.; Wolfe, S. M.; LaBombard, B.
- Nuclear Fusion, Vol. 57, Issue 8