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Motional Stark effect diagnostic pilot experiment for MAST
KTH, School of Engineering Sciences (SCI), Physics.
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2006 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 10, 10E905- p.Article in journal (Refereed) Published
Abstract [en]

Exploiting the motional Stark effect (MSE) in the low magnetic fields of spherical tokamaks such as MAST is complicated by the Doppler smearing of the relatively closely spaced Stark components. Extensive modeling of MSE spectra and the subsequent polarized fraction (similar to 20%) of spectrally filtered light and signal to noice ratios have been performed taking account of real experimental conditions including neutral beam parameters, port sizes, optical losses, filter characteristics, etc. A design is selected which uses high throughput interference filters (0.1 nm bandpass ) for separation of the spectral components. An accuracy of similar to 0.5 degrees S compared with typically 15 degrees is estimated for field angle measurements. The design allows for early implementation, starting with a pilot two chord system, and for an economic expansion to a multiplicity of chords. Matching the Doppler shifted D-alpha from the beam neutrals will be accomplished by a combination of filter selection and fine-tuning of the beam voltage. Avoiding filter tuning in the design greatly simplifies the diagnostic. Calibration results of the diagnostic support the calculations.

Place, publisher, year, edition, pages
2006. Vol. 77, no 10, 10E905- p.
Keyword [en]
Calibration, Doppler effect, Magnetic fields, Optical filters, Signal to noise ratio, Tokamak devices
National Category
Atom and Molecular Physics and Optics
URN: urn:nbn:se:kth:diva-6555DOI: 10.1063/1.2220475ISI: 000241722800138ScopusID: 2-s2.0-33750526497OAI: diva2:11300
Conference: 16th Topical Conference on High-Temperature Plasma Diagnostics. Williamsburg, VA. MAY 07-11, 2006

QC 20100907.

Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2015-04-13Bibliographically approved
In thesis
1. Diagnostics for advanced fusion plasma scenarios
Open this publication in new window or tab >>Diagnostics for advanced fusion plasma scenarios
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Over the past decade, fusion research has showed the potential of being a main candidate for energy production for future generations. Further advances in improved fusion performance are therefore vital. This thesis focuses on advanced fusion plasma scenarios and their diagnostic requirements. In particular the design of a motional Stark effect (MSE) diagnostic at the MAST spherical tokamak and the analysis of magneto-hydrodynamic mode feedback control and pulsed poloidal current drive (PPCD) at the reversed field pinch (RFP) experiment EXTRAP T2R are discussed.

The MSE diagnostic is important for the determination of the plasma current profile, information that is necessary for studies in advanced confinement scenarios like reversed shear profiles or current holes. The MAST MSE system has two channels and selects the spectral components using 1Å FWHM interference filters. The diagnostic has been commissioned during the fall of 2006 and the results show the feasibility of the technique with rms-noise ~0.5° using a time resolution of 1 ms. Investigations of mirror labyrinths for the future ITER MSE diagnostic highlight the need for careful calibration considerations.

Feedback control and PPCD are techniques for improved confinement. Feedback control dramatically decreases impurity influx at the end of discharges while transport in the bulk plasma is largely unaffected. During PPCD the transport is seen to decrease and it is demonstrated that PPCD and feedback control can be employed simultaneously.

New and innovative techniques for fusion spectroscopy are furthermore described. This includes the use of correlations in line integrated signals to determine ion emission profiles in poloidally symmetric environments. Good agreement with other diagnostic methods is obtained. The assessment of electron temperature profiles using measured differences between Thomson scattering and vacuum ultra-violet spectroscopy is also shown.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xiv, 84 p.
Trita-FYS, ISSN 0280-316X ; 2006:64
MSE, PEM, mirror evolution, fusion, diagnostics, plasma spectroscopy, reversed field pinch, spherical tokamak, intelligent shell, PPCD, MAST, ITER
National Category
Atom and Molecular Physics and Optics
urn:nbn:se:kth:diva-4221 (URN)91-7178-474-8 (ISBN)
Public defence
2006-12-15, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 09:00
QC 20100907Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2010-09-07Bibliographically approved

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