Measurement and Modeling of the Response of the Current Profile Evolution to Feedback Control Actuators in DIII-D
J.R. Ferron, P. Gohil, C.M. Greenfield, T.C. Luce, C.C. Petty, P.A. Politzer, V. Basiuk, F. Imbeaux, M. Schneider, T.A. Casper, M. Murakami, Y. Ou, E. Schuster, Q. Gao, A. Wang
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Orlando, Florida, November 12-16, 2007
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Abstract
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For closed loop control of the q evolution during the plasma current
ramp up, available actuators are electron heating power, Ip ramp rate,
electron density and co-counter beam balance to modify the net neutral
beam current drive. Measurements of the effects of these actuators
on the current profile evolution are compared to transport code
predictions from ONETWO, TRANSP, CRONOS, and CORSICA to test the model
of the plasma response in the control process. Measurements of the
dynamic response of the q evolution, particularly to electron heating,
provide input to the controller development process. A
proportional/integral controller with empirically determined gains and
provision to avoid βN excursions has been demon- strated to regulate
qmin at the start of the high-performance phase of the discharge for a
variety of initial and target conditions.
