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

Journal Article · · Nuclear Fusion
 [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)
+ Show Author Affiliations

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.

Research Organization:
General Atomics, San Diego, CA (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
FC02-04ER54698
OSTI ID:
1406917
Journal Information:
Nuclear Fusion, Vol. 57, Issue 11; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 8 works
Citation information provided by
Web of Science

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Cited By (2)

Real-time capable modeling of neutral beam injection on NSTX-U using neural networks journal March 2019
Feedback control of stored energy and rotation with variable beam energy and perveance on DIII-D journal May 2019

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
plasma control
current profile control
model-based optimization
enhanced discharge reproducibility