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Numerical studies of confinement scalings for the dynamo-free reversed-field pinch
KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.ORCID-id: 0000-0001-6379-1880
2007 (Engelska)Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 47, nr 1, s. 9-16Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In the reversed-field pinch (RFP), tearing modes associated with the dynamo are responsible for reduced energy- and particle confinement. In this study, it is observed that by implementing current profile control (CPC) in the RFP, a dynamo-free state can be achieved. The effect of CPC in the RFP is examined by the use of numerical simulations, and scaling laws are presented for confinement parameters. The model is nonlinear MHD in 3D including finite resistivity and pressure. A linear regression analysis is performed on simulation data from a series of computer runs for a set of initial parameter values. Scaling laws are determined for radial magnetic field, energy confinement time, poloidal beta and temperature. Confinement is improved substantially as compared with the conventional RFP - the temperature reaches reactor relevant levels by ohmic heating alone. It is observed that the configuration spontaneously develops into a quasi single helicity state. The CPC scheme is designed to eliminate the fluctuating electric dynamo field Ef ≤ -〈v × B〉, using feedback of an externally imposed electric field. The focus of this study is on obtaining principal theoretical optimization of confinement in the RFP by implementing CPC and to formulate scaling laws for confinement parameters, thus investigating the reactor viability of the concept.

Ort, förlag, år, upplaga, sidor
2007. Vol. 47, nr 1, s. 9-16
Nyckelord [en]
Computer simulation, Electric conductivity, Joule heating, Magnetohydrodynamics, Optimization, Plasma confinement, Regression analysis, Scaling laws
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
URN: urn:nbn:se:kth:diva-6334DOI: 10.1088/0029-5515/47/1/002ISI: 000243953900005Scopus ID: 2-s2.0-33947622628OAI: oai:DiVA.org:kth-6334DiVA, id: diva2:11019
Anmärkning
QC 20100924. Uppdaterad från Accepted till Published (20100924).Tillgänglig från: 2006-11-13 Skapad: 2006-11-13 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. Numerical studies of current profile control in the reversed-field pinch
Öppna denna publikation i ny flik eller fönster >>Numerical studies of current profile control in the reversed-field pinch
2006 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2006. s. 52
Serie
Trita-EE, ISSN 1653-5146 ; 2006:053
Nyckelord
Reversed-Field Pinch, RFP, Current Profile Control, CPC, DEBS, DEBSP, active control, feedback, MHD.
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:kth:diva-4167 (URN)91-7178-500-0 (ISBN)
Disputation
2006-11-30, Kollegiesalen (F3), Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20101101Tillgänglig från: 2006-11-13 Skapad: 2006-11-13 Senast uppdaterad: 2010-11-01Bibliografiskt granskad

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Scheffel, Jan

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