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Effect of thermal conduction on pressure-driven modes in the reversed-field pinch
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0001-6379-1880
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-7142-7103
2012 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 52, no 12, 123012- p.Article in journal (Refereed) Published
Abstract [en]

Classical linearized resistive magnetohydrodynamic (MHD) stability theory predicts unstable pressure-driven modes even at low plasma beta values for the reversed-field pinch (RFP) because of its unfavourable curvature and strong poloidal magnetic field. These resistive g-modes undermine energy confinement and are detrimental to the RFP reactor potential. In the analysis, one aspect is common, which is the usage of the adiabatic energy equation, ignoring the contribution due to thermal conduction effects. However, in recent analysis, stabilization of pressure-driven modes is demonstrated through inclusion of thermal conductivity. In this paper, we compare the results obtained from both classical and thermal conduction modified boundary layer stability analysis with those from a time-spectral resistive linearized MHD code. Ohmic heating and thermal conduction effects are included in the calculations. We have found that thermal conduction effects stabilize pressure-driven resistive g-modes only for very low values of plasma beta. In addition, analytical and numerical investigation of the equilibrium reveal that, for reactor relevant values of S-0 and tearing stable plasmas, the scaling gamma similar to S-0(-1/5) for the growth rate of these modes is weaker than that for the adiabatic case gamma similar to S-0(-1/3).

Place, publisher, year, edition, pages
2012. Vol. 52, no 12, 123012- p.
Keyword [en]
Magnetohydrodynamic Transport Model, Resistive Instabilities, Toroidal Plasma, Configurations, Systems
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-105494DOI: 10.1088/0029-5515/52/12/123012ISI: 000311754900015ScopusID: 2-s2.0-84870162299OAI: diva2:571175

QC 20130109

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2013-05-02Bibliographically approved
In thesis
1. Pressure driven instabilities in the reversed-field pinch: numerical and theoretical studies
Open this publication in new window or tab >>Pressure driven instabilities in the reversed-field pinch: numerical and theoretical studies
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

According to classical linearized resistive magnetohydrodynamics theory, pressuredriven modes are unstable in the reversed-field pinch (RFP) due to unfavorable magnetic field line curvature. The result is based on the assumption of an adiabatic energy equation where anisotropic thermal conduction effects are ignored as compared to convection and compression. In this thesis the effects of heat conduction in the energy equation have been studied. We have examined these effects on the linear stability of pressure-driven resistive modes using boundary value theory (Δ´ ) and a novel initial-value full resistive MHD code employing the Generalized Weighted Residual Method (GWRM). In the Δ´ method, a shooting technique is employed by integrating from the resistive layer to boundaries. The GWRM method, on the other hand, is a time-spectral Galerkin method in which the fully linearized MHD equations are solved. For detailed computations, efficiency requires the temporal and spatial domains to be divided into subdomains. For this purpose, a number of challenging test cases including linearized ideal MHD equations are treated.

Numerical and analytical investigations of equilibria reveal that thermal conduction effects are not stabilizing for reactor relevant values of Lundquist number, S0, and normalized pressure, βθ, for tearing-stable plasmas. These studies show that growth rate scales as  γ~_ S0−1/5 , which is weaker than for the adiabatic case, γ~_ S0−1/3.

A numerical study of optimized confinement for an advanced RFP scenario including ohmic heating and heat conduction, is also part of this thesis. The fully nonlinear resistive MHD code DEBSP has been employed. We have identified, using both Δ´ and GWRM methods, that the observed crash of the high confinement is caused by resistive, pressure-driven modes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xi, 56 p.
Trita-EE, ISSN 1653-5146 ; 2013:017
Fusion plasma, thermonuclear, Reversed-field pinch, resistive MHD, resistive g modes, thermal conduction, the boundary value theory
National Category
Fusion, Plasma and Space Physics
urn:nbn:se:kth:diva-121345 (URN)978-91-7501-722-8 (ISBN)
Public defence
2013-05-17, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)

QC 20130503

Available from: 2013-05-02 Created: 2013-04-29 Last updated: 2013-05-02Bibliographically approved

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