title: A digital control system for external magnetohydrodynamic modes in tokamak plasmas.
abstract: A feedback system for controlling external, long-wavelength magnetohydrodynamic activity is described. The system is comprised of a network of localized magnetic pickup and control coils driven by four independent, low-latency field-programable gate array controllers. The control algorithm incorporates digital spatial filtering to resolve low mode number activity, temporal filtering to correct for frequency-dependent amplitude and phase transfer effects in the control hardware, and a Kalman filter to distinguish the unstable plasma mode from noise.
authors.affiliation: Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA. jmh2130@columbia.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Hanson
authors.forename: A J
authors.initials: AJ
authors.lastname: Klein
authors.forename: M E
authors.initials: ME
authors.lastname: Mauel
authors.forename: D A
authors.initials: DA
authors.lastname: Maurer
authors.forename: G A
authors.initials: GA
authors.lastname: Navratil
authors.forename: T Sunn
authors.initials: TS
authors.lastname: Pedersen