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Title: Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D

Abstract

Here, we report increased edge electron temperature and density turbulence levels ($$\tilde{T}_e$$ and $$\tilde{n}_3$$) in Edge Localized Mode free Quiescent H-mode (ELM-free QH-mode) plasmas as compared to the ELMing time period. ELMs can severely damage plasma facing components in fusion plasma devices due to their large transient energy transport, making ELM-free operation a highly sought after goal. The QH-mode is a candidate for this goal as it is ELM-free for times limited only by hardware constraints. It is found that the driving gradients decrease during the QH-mode compared to the ELMing phase, however, a significant decrease in the ExB shearing rate is also observed that taken together is consistent with the increased turbulence. These results are significant as the prediction and control of ELM-free H-mode regimes are crucial for the operation of future fusion devices such as ITER. The changes in the linear growth rates calculated by CGYRO [Candy et al., J. Comput. Phys. 324, 73 (2016)] and the measured ExB shearing rate between ELMing and QH-mode phases are qualitatively consistent with these turbulence changes. Comparison with ELMing and 3D fields ELM suppressed H-mode finds a similar increase in $$\tilde{T}_e$$ and $$\tilde{n}_3$$, however, with distinctly different origins, the increased driving gradients rather than the changes in the ExB shearing rate in 3D fields ELM suppressed the H-mode. However, linear gyrokinetic calculation results are generally consistent with the increased turbulence in both ELM-controlled discharges.

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [3]; ORCiD logo [2];  [2];  [1]
  1. Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy
  2. General Atomics, San Diego, CA (United States)
  3. Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Engineering Physics
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Univ. of California, Los Angeles, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1540159
Alternate Identifier(s):
OSTI ID: 1426849
Grant/Contract Number:  
FC02-04ER54698; FG02-08ER54984
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
physics

Citation Formats

Sung, C., Rhodes, T. L., Staebler, G. M., Yan, Z., McKee, G. R., Smith, S. P., Osborne, T. H., and Peebles, W. A. Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D. United States: N. p., 2018. Web. doi:10.1063/1.5017964.
Sung, C., Rhodes, T. L., Staebler, G. M., Yan, Z., McKee, G. R., Smith, S. P., Osborne, T. H., & Peebles, W. A. Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D. United States. doi:10.1063/1.5017964.
Sung, C., Rhodes, T. L., Staebler, G. M., Yan, Z., McKee, G. R., Smith, S. P., Osborne, T. H., and Peebles, W. A. Mon . "Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D". United States. doi:10.1063/1.5017964. https://www.osti.gov/servlets/purl/1540159.
@article{osti_1540159,
title = {Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D},
author = {Sung, C. and Rhodes, T. L. and Staebler, G. M. and Yan, Z. and McKee, G. R. and Smith, S. P. and Osborne, T. H. and Peebles, W. A.},
abstractNote = {Here, we report increased edge electron temperature and density turbulence levels ($\tilde{T}_e$ and $\tilde{n}_3$) in Edge Localized Mode free Quiescent H-mode (ELM-free QH-mode) plasmas as compared to the ELMing time period. ELMs can severely damage plasma facing components in fusion plasma devices due to their large transient energy transport, making ELM-free operation a highly sought after goal. The QH-mode is a candidate for this goal as it is ELM-free for times limited only by hardware constraints. It is found that the driving gradients decrease during the QH-mode compared to the ELMing phase, however, a significant decrease in the ExB shearing rate is also observed that taken together is consistent with the increased turbulence. These results are significant as the prediction and control of ELM-free H-mode regimes are crucial for the operation of future fusion devices such as ITER. The changes in the linear growth rates calculated by CGYRO [Candy et al., J. Comput. Phys. 324, 73 (2016)] and the measured ExB shearing rate between ELMing and QH-mode phases are qualitatively consistent with these turbulence changes. Comparison with ELMing and 3D fields ELM suppressed H-mode finds a similar increase in $\tilde{T}_e$ and $\tilde{n}_3$, however, with distinctly different origins, the increased driving gradients rather than the changes in the ExB shearing rate in 3D fields ELM suppressed the H-mode. However, linear gyrokinetic calculation results are generally consistent with the increased turbulence in both ELM-controlled discharges.},
doi = {10.1063/1.5017964},
journal = {Physics of Plasmas},
number = 5,
volume = 25,
place = {United States},
year = {2018},
month = {3}
}

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