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Diagnosing Fuel Ions in Fusion Plasmas using Neutron Emission Spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. (Fusion diagnostics)
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. , p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 716
Keywords [en]
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: urn:nbn:se:uu:diva-114449ISBN: 978-91-554-7727-1 (print)OAI: oai:DiVA.org:uu-114449DiVA, id: diva2:294070
Public defence
2010-03-31, Häggsalen, Lägerhyddsvägen 1, Ångströmslaboratoriet, 10:15 (English)
Opponent
Supervisors
Available from: 2010-03-10 Created: 2010-02-16 Last updated: 2010-03-10Bibliographically approved
List of papers
1. Validating TRANSP simulations Using Neutron Emission Spectroscopy with Dual Sight Lines
Open this publication in new window or tab >>Validating TRANSP simulations Using Neutron Emission Spectroscopy with Dual Sight Lines
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2008 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 10, p. E510-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-114445 (URN)
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2017-12-12
2. Neutron spectroscopy measurements and modeling of neutral beam heating fast ion dynamics
Open this publication in new window or tab >>Neutron spectroscopy measurements and modeling of neutral beam heating fast ion dynamics
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2010 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 52, no 8, p. 085013-Article in journal (Refereed) Published
Abstract [en]

The energy spectrum of the neutron emission from beam-target reactions in fusion plasmas at the Joint European Torus (JET) has been investigated. Different beam energies as well as injection angles were used. Both measurements and simulations of the energy spectrum were done. The measurements were made with the time-of-flight spectrometer TOFOR. Simulations of the neutron spectrum were based on first-principle calculations of neutral beam deposition profiles and the fast ion slowing down in the plasma using the code NUBEAM, which is a module of the TRANSP package. The shape of the neutron energy spectrum was seen to vary significantly depending on the energy of the beams as well as the injection angle and the deposition profile in the plasma. Cross validations of the measured and modeled neutron energy spectra were made, showing a good agreement for all investigated scenarios.

National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-114446 (URN)10.1088/0741-3335/52/8/085013 (DOI)000279709700013 ()
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2017-12-12Bibliographically approved
3. Neutron emission generated by fast deuterons accelerated with ion cyclotron heating at JET
Open this publication in new window or tab >>Neutron emission generated by fast deuterons accelerated with ion cyclotron heating at JET
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2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 2, p. 022001-Article in journal, Letter (Refereed) Published
Abstract [en]

For the first time, the neutron emission from JET plasmas heated with combined deuterium neutral beam injection and third harmonic ion cyclotron radio frequency heating have been studied with neutron emission spectroscopy (NES). Very high DD neutron rates were observed with only modest external heating powers, which was attributed to acceleration of deuterium beam ions to energies of about 2-3 MeV, where the DD reactivity is on a par of that of the DT reaction. Fast deuterium energy distributions were derived from analysis of NES data and confirm acceleration of deuterium beam ions up to energies around 3 MeV, in agreement with theoretical predictions. The high neutron rates allowed for observations of changes in the fast deuterium populations on a time scale of 50 ms. Correlations were seen between fast deuterium ions at different energies and magnetohydrodynamic activities, such as monster sawtooth crashes and toroidal Alfvén eigenmodes.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-114441 (URN)10.1088/0029-5515/50/2/022001 (DOI)000275322200002 ()
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2017-12-12Bibliographically approved
4. Measurements of fast ions and their interactions with MHD activity using neutron emission spectroscopy
Open this publication in new window or tab >>Measurements of fast ions and their interactions with MHD activity using neutron emission spectroscopy
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2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 8, p. 084006-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.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-114442 (URN)10.1088/0029-5515/50/8/084006 (DOI)000280505800007 ()
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2018-04-23
5. Fast ion distributions from 3rd harmonic ion cyclotron resonance heating studied with neutron emission spectroscopy
Open this publication in new window or tab >>Fast ion distributions from 3rd harmonic ion cyclotron resonance heating studied with neutron emission spectroscopy
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(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:uu:diva-114444 (URN)
Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2010-02-16

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