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Title: Experimental challenges to stiffness as a transport paradigm

Two power scans were carried out in H-mode plasmas in DIII-D; one employed standard co-current neutral beam injection (NBI), while the other used a mixture of co-current and counter-current NBI to scan power while holding the torque to a low fixed value. Analysis of the ion and electron heat transport, ion toroidal angular momentum transport, and thermal deuterium transport from these scans are presented. Invariance of the gradients or gradient scalelengths, as might be expected from stiff transport, was not generally observed. When invariance was seen, it was not accompanied by a strong increase in transport, except in the case of the absolute deuterium ion transport. Conduction in the ion channel is the dominant energy loss mechanism. The variation of the ion heat transport with applied power is similar for the co-injection and fixed torque scans, indicating that ExB shearing is not determining the plasma response to additional power. There is however, a quantitative difference in the transport between the two scans, indicating ExB shearing does play a role in the transport. Comparison of these results with a previous experiment that directly probed stiffness at a single radius leads to the following conclusion: while local stiffness as formally defined maymore » hold, invariance of the gradients or normalized scalelengths does not follow from stiff transport in more practical scaling experiments, such as the power scans discussed here. Lastly, possible reasons for the lack of correspondence between the local picture and the global expectations are discussed.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [4] ;  [5] ;  [6]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of California, San Diego, CA (United States)
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  4. Univ. of Texas, Austin, TX (United States)
  5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  6. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Grant/Contract Number:
FC02-04ER54698; FG03-97ER54415; AC02-09CH11466; FG02-08ER54984
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 2; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; transport; stiffness; tokamak
OSTI Identifier:
1417186

Luce, Timothy C., Burrell, Keith H., Holland, Christopher, Marinoni, Alessandro, Petty, Craig C., Smith, Sterling P., Austin, Max E., Grierson, Brian A., and Zeng, Lei. Experimental challenges to stiffness as a transport paradigm. United States: N. p., Web. doi:10.1088/1741-4326/aa9af7.
Luce, Timothy C., Burrell, Keith H., Holland, Christopher, Marinoni, Alessandro, Petty, Craig C., Smith, Sterling P., Austin, Max E., Grierson, Brian A., & Zeng, Lei. Experimental challenges to stiffness as a transport paradigm. United States. doi:10.1088/1741-4326/aa9af7.
Luce, Timothy C., Burrell, Keith H., Holland, Christopher, Marinoni, Alessandro, Petty, Craig C., Smith, Sterling P., Austin, Max E., Grierson, Brian A., and Zeng, Lei. 2018. "Experimental challenges to stiffness as a transport paradigm". United States. doi:10.1088/1741-4326/aa9af7.
@article{osti_1417186,
title = {Experimental challenges to stiffness as a transport paradigm},
author = {Luce, Timothy C. and Burrell, Keith H. and Holland, Christopher and Marinoni, Alessandro and Petty, Craig C. and Smith, Sterling P. and Austin, Max E. and Grierson, Brian A. and Zeng, Lei},
abstractNote = {Two power scans were carried out in H-mode plasmas in DIII-D; one employed standard co-current neutral beam injection (NBI), while the other used a mixture of co-current and counter-current NBI to scan power while holding the torque to a low fixed value. Analysis of the ion and electron heat transport, ion toroidal angular momentum transport, and thermal deuterium transport from these scans are presented. Invariance of the gradients or gradient scalelengths, as might be expected from stiff transport, was not generally observed. When invariance was seen, it was not accompanied by a strong increase in transport, except in the case of the absolute deuterium ion transport. Conduction in the ion channel is the dominant energy loss mechanism. The variation of the ion heat transport with applied power is similar for the co-injection and fixed torque scans, indicating that ExB shearing is not determining the plasma response to additional power. There is however, a quantitative difference in the transport between the two scans, indicating ExB shearing does play a role in the transport. Comparison of these results with a previous experiment that directly probed stiffness at a single radius leads to the following conclusion: while local stiffness as formally defined may hold, invariance of the gradients or normalized scalelengths does not follow from stiff transport in more practical scaling experiments, such as the power scans discussed here. Lastly, possible reasons for the lack of correspondence between the local picture and the global expectations are discussed.},
doi = {10.1088/1741-4326/aa9af7},
journal = {Nuclear Fusion},
number = 2,
volume = 58,
place = {United States},
year = {2018},
month = {1}
}