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Visible spectroscopy as a sensitive diagnostic tool for fusion plasmas
KTH, School of Engineering Sciences (SCI), Physics.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

To further the understanding and knowledge about fusion plasmas and their behaviour during different conditions, it is important to be able to collect information about the plasma and the processes occurring within it. Visible spectroscopy, or the study of the visible wavelength light emitted by the plasma, is a useful tool in this search for knowledge.

This thesis is based on experiments where visible wavelength light has been measured and analysed in order to determine quantities about the emitting source. Doppler shift measurements of spectral lines have been utilised to determine the toroidal rotation velocities of plasma impurity ions and to study the correlation with mode rotation and the effect of active feedback control of the resistive wall modes. Information on the impurities present in the plasma has been determined and the calibrated intensities of spectral lines has yielded impurity concentrations, particle fluxes and electron temperature and densities. Ion temperatures have been determined from Doppler broadening measurements.

The measured vibrational and rotational band structure of deuterium molecular spectra has been analysed in order to calculate rotational and vibrational temperatures, relative populations and molecular particle fluxes. The effect of the molecular flux on simple calculations of atomic flux has also been studied. Specific molecular states and transitions of deuterium have also been probed with synchrotron radiation to study the level and transition energies.

The measurement and analysis of visible wavelength light has been demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and molecular structure.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 29 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:64
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-572ISBN: 91-7178-222-2 (print)OAI: oai:DiVA.org:kth-572DiVA: diva2:14473
Presentation
2005-12-06, Sal FA31, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20101215Available from: 2005-12-23 Created: 2005-12-23 Last updated: 2010-12-15Bibliographically approved
List of papers
1. Ion and mode rotation in the EXTRAP T2R device during discharges with and without the application of feedback control
Open this publication in new window or tab >>Ion and mode rotation in the EXTRAP T2R device during discharges with and without the application of feedback control
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2005 (English)Conference paper, Published paper (Refereed)
Series
Europhysics Conference Abstracts, 29C
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-8960 (URN)2-s2.0-84873366278 (Scopus ID)978-162276332-0 (ISBN)
Conference
32nd European Physical Society Conference on Plasma Physics and Controlled Fusion combined with the 8th International Workshop on Fast Ignition of Fusion Targets; Tarragona; Spain; 27 June 2005 through 1 July 2005
Note

QC 20101207

Available from: 2005-12-23 Created: 2005-12-23 Last updated: 2014-09-24Bibliographically approved
2. Impurity identifications, concentrations and particle fluxes from spectral measurements of the EXTRAP T2R plasma
Open this publication in new window or tab >>Impurity identifications, concentrations and particle fluxes from spectral measurements of the EXTRAP T2R plasma
2006 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 74, no 4, 439-448 p.Article in journal (Refereed) Published
Abstract [en]

An absolute intensity calibrated 0.5m spectrometer with optical multi-channel analyser detector was used to observe the visible-UV radiation from the plasma in the EXTRAP T2R reversed field pinch experiment. Spectral lines were identified indicating the presence of oxygen, chromium, iron and molybdenum impurities in the hydrogen plasma. Certain regions of interest were examined in more detail and at different times in the plasma discharge. Impurity concentration calculations were made using the absolute intensities of lines of OIV and OV measured at 1-2 ms into the discharge generating estimates of the order of 0.2% of ne in the central region rising to 0.7% of ne at greater radii for OIV and 0.3% rising to 0.6% for OV. Edge electron temperatures of 0.5-5 eV at electron densities of 5-10 x 10(11) cm(-3) were calculated from the measured relative intensities of hydrogen Balmer lines. The absolute intensities of hydrogen lines and of multiplets of neutral chromium and molybdenum were used to determine particle fluxes (at 4-5 ms into the plasma) of the order 1 x 10(16), 7 x 1013 and 3 x 10(13) particles cm(-2) s(-1), respectively.

Keyword
Carrier concentration, Impurities, Optical devices, Spectrometers, Spectrum analyzers, Ultraviolet radiation, Field pinch experiment, Multi-channel analysers, Plasma discharges, Plasmas
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-7654 (URN)10.1088/0031-8949/74/4/005 (DOI)000241682600005 ()2-s2.0-33846118810 (Scopus ID)
Note
QC 20100810Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2011-12-16Bibliographically approved
3. Molecular contribution to the D alpha emission in the divertor of the ASDEX Upgrade experiment
Open this publication in new window or tab >>Molecular contribution to the D alpha emission in the divertor of the ASDEX Upgrade experiment
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2007 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 105, no 3, 425-437 p.Article in journal (Refereed) Published
Abstract [en]

Spectral line emission from the deuterium Balmer alpha line and from molecular deuterium in the Fulcher band, d(3)Pi(u)-> a(3)Sigma(+)(g), was studied in the outer divertor region of the ASDEX Upgrade plasma with a pair of relatively calibrated spectrometers. A dependence of the signals on the proximity of the plasma strike point and on divertor gas puffing was noted. The rotational spectrum of the lowest diagonal vibrational molecular bands indicated rotational temperatures of ca. 1000 K and hence, through calculation of relative upper state populations, a ground state vibrational temperature of ca. 4000 K. Calculating the particle fluxes, the molecular deuterium was found to contribute up to 1% of the D alpha intensity, the relative importance of the molecules at some divertor heights was affected by the position of the strike point.

Keyword
ASDEX Upgrade, Calibration, Deuterium molecules, Divertor spectroscopy
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-7656 (URN)10.1016/j.jqsrt.2006.12.004 (DOI)000245564400006 ()2-s2.0-33847233592 (Scopus ID)
Note
QC 20100810Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2011-12-16Bibliographically approved
4. Active control of multiple resistive wall modes
Open this publication in new window or tab >>Active control of multiple resistive wall modes
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2005 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 47, no 12 B, B25-B36 p.Article in journal (Refereed) Published
Abstract [en]

 A two-dimensional array of saddle coils at M-c poloidal and N-c toroidal positions is used on the EXTRAP T2R reversed-field pinch (Brunsell P R et al 2001 Plasma Phys. Control. Fusion 43 1457) to study active control of resistive wall modes (RWMs). Spontaneous growth of several RWMs with poloidal mode number m = 1 and different toroidal mode number n is observed experimentally, in agreement with linear MHD modelling. The measured plasma response to a controlled coil field and the plasma response computed using the linear circular cylinder MHD model are in quantitive agreement. Feedback control introduces a linear coupling of modes with toroidal mode numbers n, n' that fulfil the condition vertical bar n - n'vertical bar = N-c. Pairs of coupled unstable RWMs are present in feedback experiments with an array of Mc x Nc = 4 x 16 coils. Using intelligent shell feedback, the coupled modes are generally not controlled even though the field is suppressed at the active coils. A better suppression of coupled modes may be achieved in the case of rotating modes by using the mode control feedback scheme with individually set complex gains. In feedback with a larger array of Mc x Nc = 4 x 32 coils, the coupling effect largely disappears, and with this array, the main internal RWMs n = -11, -10, +5, +6 are all simultaneously suppressed throughout the discharge (7-8 wall times). With feedback there is a two-fold extension of the pulse length, compared to discharges without feedback.

Keyword
Electric coils; Feedback control; Growth (materials); Magnetohydrodynamics; Mathematical models; Plasmas
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5428 (URN)10.1088/0741-3335/47/12B/S03 (DOI)000234420700005 ()2-s2.0-27744525924 (Scopus ID)
Note
QC 20100826Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2017-11-21Bibliographically approved
5. The npσ,π to EF emission systems in D2 studied by selective excitation
Open this publication in new window or tab >>The npσ,π to EF emission systems in D2 studied by selective excitation
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2005 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, no 6, 659-664 p.Article in journal (Refereed) Published
Abstract [en]

The np sigma 1 Sigma(u)(+) and np pi (1)Pi(u) states in D-2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF (1)Sigma(g)(+) state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P and R branches relative to the Q branch were found to vary strongly in the np pi (1)Pi(u)(+)-EF(1)Sigma(g)(+) bands indicating the existence of predissociations of np pi (1)Pi(u)(+) levels above the dissociation limit D(1s) + D(2l).

Keyword
Absorption spectroscopy, Dispersion (waves), Dissociation, Electric excitation, Electron energy levels, Synchrotron radiation, Dispersed emissions, Emission bands, Grating spectrometers, Molecular hydrogen
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7997 (URN)10.1088/0953-4075/38/6/004 (DOI)000228455000008 ()2-s2.0-16244367150 (Scopus ID)
Note
QC 20100916Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2010-09-16Bibliographically approved

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