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Title: Closed Loop Feedback of MHD Instabilities on DIII-D

Closed Loop Feedback of MHD Instabilities on DIII-D A system of coils, sensors and amplifiers has been installed on the DIII-D tokamak to study the physics of feedback stabilization of low-frequency MHD [magnetohydrodynamic] modes such as the Resistive Wall Mode (RWM). Experiments are being performed to assess the effectiveness of this minimal system and benchmark the predictions of theoretical models and codes. In the last campaign, the experiments have been extended to a regime where the RWM threshold is lowered by a fast ramp of the plasma current. In these experiments, the onset time of the RWM is very reproducible. With this system, the onset of the RWM has been delayed by up to 100 msec without degrading plasma performance. The growth rate of the mode increases proportional to the length of delay, suggesting that the plasma is evolving towards a more unstable configuration. The present results have suggested directions for improving the feedback system including better sensors and improved feedback algorithms.
Authors: ; ; ; ; ;
Publication Date:
OSTI Identifier:OSTI ID: 773356
Report Number(s):PPPL-3535
TRN: US0100740
DOE Contract Number:AC02-76CH03073
Resource Type:Technical Report
Resource Relation:Other Information: PBD: 16 Jan 2001
Research Org:Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org:USDOE Office of Energy Research (ER) (US)
Country of Publication:United States
Language:English
Subject: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALGORITHMS; AMPLIFIERS; BENCHMARKS; CONFIGURATION; DOUBLET-3 DEVICE; FEEDBACK; PERFORMANCE; PHYSICS; PLASMA; STABILIZATION