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Study of the confinement properties in a reversed-field pinch with mode rotation and gas fuelling
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
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2002 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 44, no 8, 1625-1638 p.Article in journal (Refereed) Published
Abstract [en]

An extensive investigation of the global confinement properties in different operating scenarios in the rebuilt EXTRAP T2R reversed-field pinch (RFP) experiment is reported here. In particular, the role of a fast gas puff valve system, used to control plasma density, on confinement is studied. Without gas puffing, the electron density decays below 0.5 x 10(19) M-3. The poloidal beta varies between 5% and 15%, decreasing at large I/N. The energy confinement time ranges from 70 to 225 mus. With gas puffing, the density is sustained at n(e) approximate to 1.5 x 10(19) m(-3). However, a general slight deterioration of the plasma performances is observed for the same values of I/N: the plasma becomes cooler and more radiative. The poloidal beta is comparable to that in the scenarios without puff but the energy confinement time drops ranging from 60 to 130 mus. The fluctuation level and the energy confinement time have been found to scale with the Lundquist number as S-0.05+/-0.07 and S0.5+/-0.1, respectively. Mode rotation is typical for all the discharges and rotation velocity is observed to increase with increasing electron diamagnetic velocity.

Place, publisher, year, edition, pages
BRISTOL, ENGLAND: IOP PUBLISHING LTD , 2002. Vol. 44, no 8, 1625-1638 p.
Keyword [en]
POLOIDAL CURRENT DRIVE, ENERGY CONFINEMENT, RFX, FLUCTUATIONS, VUV
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-13022DOI: 10.1088/0741-3335/44/8/314ISI: 000178020200016OAI: oai:DiVA.org:kth-13022DiVA: diva2:320230
Note
QC 20100524Available 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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