Active Control of 2/1 Magnetic Islands in the HBT-EP Tokamak

Conference · Tue Nov 18 04:00:00 EST 1997

OSTI ID:761627

Navratil, G A ^[1]; Cates, C; Mauel, M E; Maurer, D; Nadle, D; Taylor, E; Xiao, Q; Wurden, G A; Reass, W A

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1. Los Alamos National Laboratory

Closed and open loop control techniques were applied to growing m/n=2/1 rotating islands in wall stabilized plasmas in the HBT-EP tokamak. The approach taken by HBT-EP combines an adjustable segmented conducting wall (which slows the growth or stabilizes ideal external kinks) with a number of small (6{degree} wide) saddle coils located between the gaps of the conducting wall. In this paper we report demonstration of 2-phase island rotation control from 5 kHz to 15 kHz and observation of the phase instability which are well modeled by the single-helicity, predictions of nonlinear Rutherford island dynamics for 2/1 tearing modes including important effects of ion inertia and FLR which appears as a damping term in the model equations. The closed loop response of active feedback control of the 2/1 mode at moderate gain was observed to be in good agreement with the theory. We have also demonstrated suppression of the 2/1 island growth using an asynchronous frequency modulation drive which maintains the flow damping of the island by application of rotating control fields with frequencies alternating above and below the natural mode frequency. This frequency modulation control technique was also able to prevent disruptions normally observed to follow giant sawtooth crashes in the plasma core.

• Research Organization: Los Alamos National Lab., NM (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 761627
• Report Number(s): LA-UR-98-45
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DAMPING
FEEDBACK
FREQUENCY MODULATION
INSTABILITY
ISLANDS
MAGNETIC ISLANDS
OPEN-LOOP CONTROL
PLASMA
ROTATION