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Measurements of fast ions and their interactions with MHD activity using neutron emission spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. (Fusion diagnostics)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
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2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 8, 084006- p.Article in journal (Refereed) Published
Abstract [en]

Ion cyclotron radio frequency (ICRF) heating can produce fast ion populations with energies reaching up to several megaelectronvolts. Here, we present unique measurements of fast ion distributions from an experiment with 3rd harmonic ICRF heating on deuterium beams using neutron emission spectroscopy (NES). From the experiment, very high DD neutron rates were observed, using only modest external heating powers. This was attributed to acceleration of deuterium beam ions to energies up to about 2-3 MeV, where the DD reactivity is on a par with that of the DT reaction. The high neutron rates allowed for observations of changes in the fast deuterium energy distribution on a time scale of 50 ms. Clear correlations were seen between fast deuterium ions in different energy ranges and magnetohydrodynamic activities, such as monster sawteeth and toroidal Alfven eigen modes (TAE). Specifically, NES data showed that the number of deuterons in the region between 1 and 1.5 MeV were decaying significantly during strong TAE activity, while ions with lower energies around 500 keV were not affected. This was attributed to resonances with the TAE modes.

Place, publisher, year, edition, pages
2010. Vol. 50, no 8, 084006- p.
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-114442DOI: 10.1088/0029-5515/50/8/084006ISI: 000280505800007OAI: oai:DiVA.org:uu-114442DiVA: diva2:294066
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2017-12-12
In thesis
1. Diagnosing Fuel Ions in Fusion Plasmas using Neutron Emission Spectroscopy
Open this publication in new window or tab >>Diagnosing Fuel Ions in Fusion Plasmas using Neutron Emission Spectroscopy
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Neutron emission spectra, measured with the time of flight spectrometer TOFOR, at the joint European torus (JET) are presented in this thesis. TOFOR has been in use since 2005, routinely measuring the neutron emission from JET plasmas.

The work in the thesis mainly concerns the modeling of the signatures in the neutron spectrum that reveal different parts of the fuel ion distribution, such as the thermal bulk plasma as well as energetic ions from neutral beam and ion cyclotron heating. Parametric models of the signatures, using plasma parameters as input, are employed to generate trial neutron spectra. The parameters, such as the fuel ion temperature or the fast ion distribution function, are deduced by iteratively fitting the trial spectra to the measured data. Measurements with TOFOR have been made and the models were applied. The studies are mainly on neutrons from d(d, n)3 He reactions(DD), although the emission from reactions with the plasma impurity 9 Be and triton burn up is covered as well.

This has allowed for detailed studies of e.g. the physics ICRF heating as well as the interactions between energetic ions and plasma instabilities, such as toroidal Alfvé Eigenmodes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 716
Keyword
fusion, plasma diagnostics, neutron spectroscopy, NBI heating, ICRF heating, energetic ions
National Category
Fusion, Plasma and Space Physics Subatomic Physics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-114449 (URN)978-91-554-7727-1 (ISBN)
Public defence
2010-03-31, Häggsalen, Lägerhyddsvägen 1, Ångströmslaboratoriet, 10:15 (English)
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Available from: 2010-03-10 Created: 2010-02-16 Last updated: 2010-03-10Bibliographically approved

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Hellesen, CarlGatu Johnson, MariaAndersson Sundén, ErikConroy, SeanEricsson, GöranEriksson, JacobSjöstrand, HenrikWeiszflog, Matthias

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