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Title: Remote feedback stabilization of tokamak instabilities

A novel remote suppressor consisting of an injected ion beam has been used for the stabilization of plasma instabilities. A collisionless curvature-driven trapped-particle instability, an [bold E][times][bold B] flute mode and an ion temperature gradient (ITG) instability have been successfully suppressed down to noise levels using this scheme. Furthermore, the first experimental demonstration of a multimode feedback stabilization with a single sensor--suppressor pair has been achieved. Two modes (an [bold E][times][bold B] flute and an ITG mode) were simultaneously stabilized with a simple state-feedback-type method where more state'' information was generated from a single-sensor Langmuir probe by appropriate signal processing. The above experiments may be considered as paradigms for controlling several important tokamak instabilities. First, feedback suppression of edge fluctuations in a tokamak with a suitable form of insulated segmented poloidal limiter sections used as Langmuir-probe-like suppressors is proposed. Other feedback control schemes are proposed for the suppression of electrostatic core fluctuations via appropriately phased ion density input from a modulated neutral beam. Most importantly, a scheme to control major disruptions in tokamaks via feedback suppression of kink (and possibly) tearing modes is discussed. This may be accomplished by using a modulated neutral beam suppressor in a feedback loop, whichmore » will supply a momentum input of appropriate phase and amplitude. Simple theoretical models predict modest levels of beam energy, current, and power.« less
Authors:
 [1]
  1. (Plasma Physics Laboratory, Columbia University, New York, New York 10027 (United States))
Publication Date:
OSTI Identifier:
5006912
DOE Contract Number:
FG02-87ER53257
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; (United States); Journal Volume: 1:5
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; TOKAMAK DEVICES; PLASMA INSTABILITY; FEEDBACK; FLUTE INSTABILITY; ION TEMPERATURE; KINK INSTABILITY; LANGMUIR PROBE; TEARING INSTABILITY; TRAPPED-PARTICLE INSTABILITY; CLOSED PLASMA DEVICES; ELECTRIC PROBES; INSTABILITY; PLASMA MACROINSTABILITIES; PROBES; THERMONUCLEAR DEVICES 700340* -- Plasma Waves, Oscillations, & Instabilities-- (1992-); 700310 -- Plasma Confinement-- (1992-)