Feedback control of vertical instability in TNS

Technical Report · Mon May 01 04:00:00 EDT 1978

DOI:https://doi.org/10.2172/6503997· OSTI ID:6503997

Frantz, E. R.

Due to the unfavorable curvature of the vertical vacuum magnetic field, elongated plasmas are vertically unstable when the elongation, epsilon, becomes too large. The TNS (The Next Step) tokamak, as evolved in the Westinghouse-ORNL studies has an inside-D configuration (epsilon = 1.6, A = 5/1.25 = 4) characterized by an average decay index n approximately equal -0.75 at the plasma flux surface near the magnetic axis and is vertically unstable with a growth rate ..gamma../sub 0/ approximately 10/sup 5/ sec/sup -1/. Eddy currents produced in the vacuum vessel wall will slow this instability to growth rates ..gamma../sub 0/ approximately 10/sup 2/ sec/sup -1/ provided there are no transverse insulating gaps in the vessel wall. A matrix equation has been developed for calculating the eddy currents induced in the EF coils and their stabilizing effect. Control theory for feedback systems with and without delay time is presented and possible plasma position detectors are discussed. For a plasma current of 6.1 MA, the controller peak power requirements using separate controller circuits are approximately 1 MW depending upon EF coil configurations and time delay. This feedback system is designed to stabilize a maximum plasma excursion of 10 cm from the midplane with delay times up to 2 sec.

• Research Organization: Westinghouse Electric Corp., Pittsburgh, PA (USA). Fusion Power Systems Dept.
• OSTI ID: 6503997
• Report Number(s): WFPS-TME-089
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
CONTROL SYSTEMS
CURRENTS
EDDY CURRENTS
ELECTRIC CURRENTS
FEEDBACK
INSTABILITY
INSTABILITY GROWTH RATES
MAGNETIC FIELDS
PLASMA INSTABILITY
THERMONUCLEAR REACTORS
TNS REACTORS
TOKAMAK TYPE REACTORS