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Ultra-high beta in numerical simulations of a tearing-mode reduced reversed-field pinch
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.ORCID iD: 0000-0001-6379-1880
2007 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 47, no 9, 1184-1188 p.Article in journal (Refereed) Published
Abstract [en]

In the advanced reversed-field pinch (RFP), current profile control (CPC) enables energy confinement time and poloidal beta to increase substantially as compared with the conventional RFP due to reduced magnetic field stochasticity. Numerical simulations using the three-dimensional non-linear resistive MHD-code DEBSP are performed showing that the poloidal beta is not limited to the m ≤ 0 stability criterion βθ < 1/2. Instead, as tearing modes are diminished, it may approach unity. The beta criterion is theoretically analysed and a new, more general, criterion is derived. Analytic estimates of the resistive tearing and g-mode growth rates are derived for m ≤ 0, and it is shown that both tearing and g-mode growth rates decrease significantly as CPC is employed. Furthermore, quasi-steady state operation with increased confinement due to active control of the current profile is numerically demonstrated for the advanced RFP for a scenario with βθ < 1/2.

Place, publisher, year, edition, pages
2007. Vol. 47, no 9, 1184-1188 p.
Keyword [en]
Betatrons, Computer simulation, Magnetic fields, Magnetohydrodynamics
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6335DOI: 10.1088/0029-5515/47/9/015ISI: 000249968800018Scopus ID: 2-s2.0-34548236281OAI: oai:DiVA.org:kth-6335DiVA: diva2:11020
Note
QC 20101005. Uppdaterad från Submitted till Published (20101005).Available from: 2006-11-13 Created: 2006-11-13 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Numerical studies of current profile control in the reversed-field pinch
Open this publication in new window or tab >>Numerical studies of current profile control in the reversed-field pinch
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The Reversed-Field Pinch (RFP) is one of the major alternatives for realizing energy production from thermonuclear fusion. Compared to alternative configurations (such as the tokamak and the stellarator) it has some advantages that suggest that an RFP reactor may be more economic. However, the conventional RFP is flawed with anomalously large energy and particle transport (which leads to unacceptably low energy confinement) due to a phenomenon called the "RFP dynam".

The dynamo is driven by the gradient in the plasma current in the plasma core, and it has been shown that flattening of the plasma current profile quenches the dynamo and increases confinement. Various forms of current profile control schemes have been developed and tested in both numerical simulations and experiments.

In this thesis an automatic current profile control routine has been developed for the three-dimensional, non-linear resistive magnetohydrodynamic computer code DEBSP. The routine utilizes active feedback of the dynamo associated fluctuating electric field, and is optimized for replacing it with an externally supplied field while maintaining field reversal. By introducing a semi-automatic feedback scheme, the number of free parameters is reduced, making a parameter scan feasible. A scaling study was performed and scaling laws for the confinement of the advanced RFP (an RFP with enhanced confinement due to current profile control) have been obtained.

The conclusions from this research project are that energy confinement is enhanced substantially in the advanced RFP and that poloidal beta values are possible beyond the previous theoretical limit beta βΘ < ½. Scalings toward the reactor regime indicate strongly enhanced confinement as compared to conventional RFP scenarios, but the question of reactor viability remains open.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 52 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:053
Keyword
Reversed-Field Pinch, RFP, Current Profile Control, CPC, DEBS, DEBSP, active control, feedback, MHD.
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-4167 (URN)91-7178-500-0 (ISBN)
Public defence
2006-11-30, Kollegiesalen (F3), Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101101Available from: 2006-11-13 Created: 2006-11-13 Last updated: 2010-11-01Bibliographically approved

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Scheffel, Jan

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