Real-time Mirror Steering for Improved Closed Loop NTM Suppression by ECCD in DIII-D
Authors: E. Kolemen, R. Ellis, R.J. La Haye, D.A. Humphreys, J. Lohr, S. Noraky, B.G. Penaflor, and A.S. Welander
Abstract:
The development and operation of the neoclassical tearing mode (NTM) avoidance and control system for
DIII-D, which uses six sets of real-time steerable mirrors in order to move the electron cyclotron current drive
(ECCD) deposition location in plasma, is described. The real-time DIII-D NTM control algorithm residing in the
Plasma Control System (PCS) automatically detects an NTM by analysis of the Mirnov diagnostics, employs
motional Stark effect (MSE) EFIT MHD equilibrium reconstruction to locate the NTM island location, then
calculates the appropriate mirror position for alignment of the ECCD with the island using ray tracing. The control
commands from PCS are sent to the electron cyclotron system to switch on and off or modulate the gyrotrons and
to the steerable mirror system to move the steerable mirrors to the requested positions. Successful NTM
suppression has been achieved in DIII-D using this control system to rapidly align the NTM island and the ECCD
deposition location, and to actively maintain the alignment as plasma conditions change.
__________________________________________________
Submitted to: SOFE 2013 Proeedings (June 0213) 25th Symposium on Fusion Engineering, San Francisdco, CA (June 10-14, 2013)
__________________________________________________
Download PPPL-4900 (pdf 266 KB 4 pp)
__________________________________________________