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Impurity identifications, concentrations and particle fluxes from spectral measurements of the EXTRAP T2R plasma
KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
KTH, School of Engineering Sciences (SCI), Physics.
KTH, School of Engineering Sciences (SCI), Physics.ORCID iD: 0000-0001-7389-5501
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.

Place, publisher, year, edition, pages
2006. Vol. 74, no 4, 439-448 p.
Keyword [en]
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: urn:nbn:se:kth:diva-7654DOI: 10.1088/0031-8949/74/4/005ISI: 000241682600005Scopus ID: 2-s2.0-33846118810OAI: oai:DiVA.org:kth-7654DiVA: diva2:12749
Note
QC 20100810Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2011-12-16Bibliographically approved
In thesis
1. Visible spectroscopic diagnostics: application and development in fusion plasmas
Open this publication in new window or tab >>Visible spectroscopic diagnostics: application and development in fusion plasmas
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diagnostic measurements play a vital role in experiments. Without them we would be in the dark with no way of knowing what was happening; of understanding the processes and behaviour occurring; or even of judging the success or failure of our experiments. The development of fusion plasma devices is no different. In this thesis we concentrate on visible spectroscopy based diagnostics: examining the techniques for measurement and analysis; the breadth of plasma parameters that can be extracted from the spectroscopic data; and how the application of these diagnostic techniques gives us a broader picture of the plasma and the events taking place within. Techniques are developed and applied to plasmas in three fusion experiments, EXTRAP T2R, ASDEX Upgrade and JET. The diagnostic techniques exploit different features of the measurements of the emitted photons to obtain various useful plasma parameters.

Determination of the ion temperature and rotation velocity of oxygen impurity ions in the EXTRAP T2R plasma is achieved through measurement and analysis of, respectively, the Doppler broadening and the Doppler wavelength shift of visible wavelength atomic spectral lines. The evolution of the temperature and rotation is studied as a function of the discharge parameters, in particular looking at the effect of applying active feedback control schemes to the resistive wall modes and/or pulsed poloidal current drive. Measurements of multiple ionisation stages are used to estimate radial profiles of the toroidal rotation and the ion temperature and correlations between the ion rotations and the rotation velocities of tearing modes are also established.

Radial profiles of the emissivity and density (or concentration) of the oxygen ions are obtained by means of measurements of the spectral line intensities on a small array of linesof- sight through the plasma. Changes to the profiles for different plasma schemes and the implications for particle transport are investigated. The derived emissivity profiles are used in the analysis for some of the other spectroscopic diagnostics. Spectral line intensity measurements (in this case of neutral ions) are also the basis for calculations of both the electron temperature and the particle fluxes at the plasma edge. The latter is an indicator of the degree and type of interaction between the plasma and the surrounding surfaces. Particle fluxes of the operating gas hydrogen and of chromium and molybdenum impurities are investigated in EXTRAP T2R for different operating scenarios, in particular changes in the metallic influx with the application of active feedback mode control are examined along with the correspondence between spectroscopic and collector probe results. In the ASDEX Upgrade divertor estimates of the particle flux of the deuterium operating gas are also made through analysis of spectral intensities. Molecular D2 band structure is explored in addition to the Balmer Dα spectral line intensity to acquire both atomic and molecular particle fluxes, investigate the contribution of the dissociating D2 to the Dα line and study the effect of changes in the divertor.

Analysis of the D2 molecular band structure (the relative intensities of the rotational lines and vibrational bands) also enables calculation of the upper state rotational and ground state vibrational temperatures. The locations of emitting atomic ions in JET are estimated from Zeeman splitting analysis of the structure of their spectral lines.

The measurement and analysis of visible wavelength light is demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and their operating scenarios.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 52 p.
Series
Trita-FYS, ISSN 0280-316X ; 2007:72
Keyword
visible spectroscopy, fusion, Doppler shift, Doppler broadening
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-4541 (URN)978-91-7178-771-2 (ISBN)
Public defence
2007-12-07, Sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100810Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2010-08-10Bibliographically approved
2. Visible spectroscopy as a sensitive diagnostic tool for fusion plasmas
Open this publication in new window or tab >>Visible spectroscopy as a sensitive diagnostic tool for fusion plasmas
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:nbn:se:kth:diva-572 (URN)91-7178-222-2 (ISBN)
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

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