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Initial results from the rebuilt EXTRAP T2R RFP device
KTH, Superseded Departments, Alfvén Laboratory. (Fusion Plasma Physics)ORCID iD: 0000-0002-5259-0458
KTH, Superseded Departments, Alfvén Laboratory. (Fusion Plasma Physics)
KTH, Superseded Departments, Alfvén Laboratory. (Fusion Plasma Physics)
KTH, Superseded Departments, Alfvén Laboratory. (Fusion Plasma Physics)
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2001 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 43, no 11, 1457-1470 p.Article in journal (Refereed) Published
Abstract [en]

The EXTRAP T2R thin shell reversed-field pinch (RFP) device has recently resumed operation after a major rebuild including the replacement of the graphite armour with molybdenum limiters, a fourfold increase of the shell time constant, and the replacement of the helical coil used for the toroidal field with a conventional solenoid-type coil. Wall-conditioning using hydrogen glow discharge cleaning was instrumental for successful RFP operation. Carbon was permanently removed from the walls during the first week of operation. The initial results from RFP operation with relatively low plasma currents in the range I-p = 70-100 kA are reported. RFP discharges are sustained for more than three shell times. Significant improvements in plasma parameters are observed, compared to operation before the rebuild. There is a substantial reduction in the carbon impurity level. The electron density behaviour is more shot-to-shot reproducible. The typical density is n(e) = 0.5-1 x 10(19) m(-3). Monitors of H-alpha line radiation indicate that the plasma wall interaction is more toroidally symmetric and that there is less transient gas release from the wall. The minimum loop voltage is in the range V-t = 28-35 V, corresponding to a reduction by a factor of two to three compared to the value before the rebuild.

Place, publisher, year, edition, pages
BRISTOL. ENGLAND: IOP PUBLISHING LTD , 2001. Vol. 43, no 11, 1457-1470 p.
Keyword [en]
REVERSED-FIELD PINCH, RESISTIVE-SHELL, TOROIDAL PINCH, FLUCTUATIONS, WALL
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-13016ISI: 000172457100003OAI: oai:DiVA.org:kth-13016DiVA: diva2:320211
Note
QC 20100524 QC 20120206Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Experimental studies of confinement in the EXTRAP T2 and T2R reversed field pinches
Open this publication in new window or tab >>Experimental studies of confinement in the EXTRAP T2 and T2R reversed field pinches
2003 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The confinement properties of fusion plasmas are affected bymagnetic and electrostatic fluctuations. The determination ofthe plasma confinement properties requires the measurement ofseveral global and local quantities such as the ion andelectron temperatures, the electron and neutral densityprofiles, the radiation emissivity profiles, the ohmic inputpower and the particle and heat diffusivities. The focus ofthis thesis is the study of the plasma confinement propertiesbased on measurements of these quantities under differentexperimental conditions.

The studies have been carried out on the reversed fieldpinch experiments EXTRAP T2 and T2R at the AlfvénLaboratory, Royal Institute of Technology (KTH) in Stockholm.Studies carried out in EXTRAP T2 were focused on dynamoactivity and on the effect of phase alignment and locking tothe wall of magnetic instabilities. These were observed with adedicated imaging system. The experimental studies in EXTRAPT2R were focused on the measurement of the confinementproperties of different configurations. To this aim, a set ofdiagnostics were used some of which were upgraded, such as theinterferometer, while others were newly installed, such as aneutral particle energy analyser and a bolometer array.

The dynamo, which is responsible for the plasma sustainment,involves resistive magnetohydrodynamic instabilities thatenhance stochastic transport. Furthermore, the plasmaconfinement properties are in general improved in the presenceof mode rotation. The possibility of reducing the stochastictransport and thereby further improving the confinement hasbeen demonstrated in a current profile control experiment.These results indicate that long pulse operations with aresisitive shell and current profile control are indeedfeasible.

KeywordsEXTRAP T2, T2R, reversed field pinch, dynamo,energy confinement time, transport, CCD, bolometer,interferometer, neutral particle energy analyser, PPCD, MonteCarlo

Place, publisher, year, edition, pages
Stockholm: KTH, 2003. x, 135 p.
Keyword
extap t2, extrap t2r, reversed field pinch
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-3468 (URN)91-7283-417-X (ISBN)
Public defence
2003-01-31, 00:00 (English)
Note
QC 20100524Available from: 2003-02-06 Created: 2003-02-06 Last updated: 2010-05-24Bibliographically approved

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Brunsell, Per

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