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Title: Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q min = 1.3,q 95 = 4:4; Target 2: q min = 1.65,q 95 = 5.0; Target 3: q min = 2.1,q 95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme is a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and alsomore » how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2]
  1. Lehigh Univ., Bethlehem, PA (United States)
  2. General Atomics, San Diego, CA (United States)
Publication Date:
Grant/Contract Number:
FC02-04ER54698
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 11; 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; plasma control; current profile control; model-based optimization; enhanced discharge reproducibility
OSTI Identifier:
1406917

Schuster, Eugenio J., Wehner, William P., Barton, Joseph E., Boyer, Mark D., Luce, Timothy C., Ferron, John R., Holcomb, Christopher T., Walker, Michael L., Humphreys, David A., Solomon, Wayne M., Penaflor, Benjamin G., and Johnson, Robert D.. Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D. United States: N. p., Web. doi:10.1088/1741-4326/aa7cab.
Schuster, Eugenio J., Wehner, William P., Barton, Joseph E., Boyer, Mark D., Luce, Timothy C., Ferron, John R., Holcomb, Christopher T., Walker, Michael L., Humphreys, David A., Solomon, Wayne M., Penaflor, Benjamin G., & Johnson, Robert D.. Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D. United States. doi:10.1088/1741-4326/aa7cab.
Schuster, Eugenio J., Wehner, William P., Barton, Joseph E., Boyer, Mark D., Luce, Timothy C., Ferron, John R., Holcomb, Christopher T., Walker, Michael L., Humphreys, David A., Solomon, Wayne M., Penaflor, Benjamin G., and Johnson, Robert D.. 2017. "Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D". United States. doi:10.1088/1741-4326/aa7cab. https://www.osti.gov/servlets/purl/1406917.
@article{osti_1406917,
title = {Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D},
author = {Schuster, Eugenio J. and Wehner, William P. and Barton, Joseph E. and Boyer, Mark D. and Luce, Timothy C. and Ferron, John R. and Holcomb, Christopher T. and Walker, Michael L. and Humphreys, David A. and Solomon, Wayne M. and Penaflor, Benjamin G. and Johnson, Robert D.},
abstractNote = {Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: qmin = 1.3,q95 = 4:4; Target 2: qmin = 1.65,q95 = 5.0; Target 3: qmin = 2.1,q95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme is a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.},
doi = {10.1088/1741-4326/aa7cab},
journal = {Nuclear Fusion},
number = 11,
volume = 57,
place = {United States},
year = {2017},
month = {8}
}