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Resistive wall modes in the EXTRAP T2R reversed-field pinch
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0002-5259-0458
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
2003 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 10, 3823- p.Article in journal (Refereed) Published
Abstract [en]

Resistive wall modes (RWM) in the reversed field pinch are studied and a detailed comparison of experimental growth rates and linear magnetohydrodynamic (MHD) theory is made. RWM growth rates are experimentally measured in the thin shell device EXTRAP T2R [P. R. Brunsell , Plasma Phys. Controlled Fusion 43, 1 (2001)]. Linear MHD calculations of RWM growth rates are based on experimental equilibria. Experimental and linear MHD RWM growth rate dependency on the equilibrium profiles is investigated experimentally by varying the pinch parameter Theta=B-theta(a)/<B-phi> in the range Theta=1.5-1.8. Quantitative agreement between experimental and linear MHD growth rates is seen. The dominating RWMs are the internal on-axis modes (having the same helicity as the central equilibrium field). At high Theta, external nonresonant modes are also observed. For internal modes experimental growth rates decrease with Theta while for external modes, growth rates increase with Theta. The effect of RWMs on the reversed-field pinch plasma performance is discussed.

Place, publisher, year, edition, pages
2003. Vol. 10, 3823- p.
Keyword [en]
magnetohydrodynamic stability, shell, instabilities, configurations, rotation, distant, hbtx1c
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5423DOI: 10.1063/1.1604775ISI: 000185422500003OAI: oai:DiVA.org:kth-5423DiVA: diva2:9785
Note
QC 20100929Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2017-11-21Bibliographically approved
In thesis
1. Resistive Wall Mode Stability and Control in the Reversed Field Pinch
Open this publication in new window or tab >>Resistive Wall Mode Stability and Control in the Reversed Field Pinch
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Control of MHD instabilities using a conducting wall together with external magnetic fields is an important route to improved performance and reliability in fusion devices. Active control of MHD modes is of interest for both the Advanced Tokamak and the Reversed Field Pinch (RFP) configurations. A wide range of unstable, current driven MHD modes is present in the RFP. An ideally conducting wall facing the plasma can in principle provide stabilization to these modes. However, a real, resistive wall characterized by a wall field diffusion time, cannot stabilize the ideal MHD modes unless they rotate with Alfvénic velocity, which is usually not the case. With a resistive wall, the ideal modes are converted into resistive wall modes (RWM) with growth rates comparable to the inverse wall time. Resistive wall modes have been studied in the EXTRAP T2R thin shell RFP device. Growth rates have been measured and found in agreement with linear MHD stability calculations. An advanced system for active control has been developed and installed on the EXTRAP T2R device. The system includes an array of 128 active saddle coils, fully covering the torus surface. Experiments on EXTRAP T2R have for the first time demonstrated simultaneous active suppression of multiple independent RWMs. In experiments with a partial array, coupling of different modes due to the limited number of feedback coils has been observed, in agreement with theory. Different feedback strategies, such as the intelligent shell, the rotating shell, and mode control have been studied. Further, feedback operation with different types of magnetic field sensors, measuring either the radial or the toroidal field components have been compared

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. viii, 46 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:005
Keyword
Resistive wall modes, RWM, active control, feedback, MHD modes, Reversed-Field pinch, RFP, intelligent shell, mode control
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-3867 (URN)91-7178-285-0 (ISBN)
Public defence
2006-03-17, H1, Teknikringen 33, Stockholm, 10:30
Opponent
Supervisors
Note
QC 20100929Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-09-29Bibliographically approved

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