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Neutron emission from a tritium rich fusion plasma: simulations in view of a possible future d-t campaign at JET
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.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
2012 (English)In: 39th EPS Conference on Plasma Physics 2012 (EPS 2012): Europhysics Conference Abstracts, 2012Conference paper, Published paper (Other academic)
Abstract [en]

 Neutron energy spectra from the t(t,2n)4He (t-t) reaction has been calculated for different fuel ion distributions, in order to assess the possibility to use this reaction when analyzing neutron spectrometry data from plasmas with very high tritium fraction. The shape of the neutron spectrum is determined by three-body kinematics, and is modified by interactions between the reaction products, primarily between the neutron and the 4He. The results indicate that the analysis of a t-t spectrum will be more challenging than for the d-t and d-d reactions. However, for fast ions in the MeV range, produced e.g. by harmonic radiofrequency heating and neutral beam injection, it should still be possible to obtain fast ion information from the neutron spectrum.

Place, publisher, year, edition, pages
2012.
Keyword [en]
nuclear fusion, neutron spectrometry, fast ions
National Category
Fusion, Plasma and Space Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-192532OAI: oai:DiVA.org:uu-192532DiVA: diva2:599862
Conference
39th EPS Conference on Plasma Physics 2012, EPS 2012, 2 - 6 July 2012, Stockholm, Sweden
Available from: 2013-01-22 Created: 2013-01-22 Last updated: 2016-01-25
In thesis
1. Fuel ion densities and distributions in fusion plasmas: Modeling and analysis for neutron emission spectrometry
Open this publication in new window or tab >>Fuel ion densities and distributions in fusion plasmas: Modeling and analysis for neutron emission spectrometry
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Neutrons produced in fusion reactions in a magnetically confined plasma carry information about the distributions and densities of the fuel ions in the plasma. This thesis presents work where various theoretical models of different fuel ion distributions in the plasma are used to calculate modeled components of the neutron energy spectrum. The calculated components can then be compared with measured data, either to benchmark and validate the model or to derive various plasma parameters from the experimental data. Neutron spectra measured with the spectrometers TOFOR and the MPR, which are both installed at the JET tokamak in England, are used for this purpose. The thesis is based on three papers.

The first paper presents the analysis of TOFOR data from plasmas heated with neutral beams and radio frequency waves tuned to the third harmonic of the deuterium cyclotron frequency, which creates fast (supra thermal) ions in the MeV range. It is found that effects of the finite Larmor radii of the fast ions need to be included in the modeling in order to understand the data. These effects are important for fast ion measurements if there is a gradient in the fast ion distribution function with a scale length that is comparable to - or smaller than - the width of the field of view of the measuring instrument, and if this scale length is comparable to - or smaller than - the Larmor radii of the fast ions.

The second paper presents calculations of the neutron energy spectrum from the T(t,n)4He reaction, for JET relevant fuel ion distributions. This is to to form a starting point for the investigation of the possibility to obtain fast ion information from the t-t neutron spectrum, in a possible future deuterium-tritium campaign at JET. The t-t spectrum is more challenging to analyze than the d-d and d-t cases, since this reaction has three (rather than two) particles in the final state, which results in a broad continuum of neutron energies rather than a peak. However, the presence of various final state interactions - in particular between the neutron and the 4He - might still allow for spectrometry analysis.

Finally, in Paper III, a method to derive the fuel ion ratio, nt/nd, is presented and applied to MPR data from the JET d-t campaign in 1997. The trend in the results are consistent with Penning trap measurements of the fuel ion ratio at the plasma edge, but the absolute numbers are not the same. Measuring the fuel ion ratio in the core plasma is an important task for fusion research, and also a very complicated one. Future work should aim at measuring this quantity in several independent ways, which should then be cross checked against each other.

Place, publisher, year, edition, pages
Uppsala: Department of Physics and Astronomy, Uppsala University, 2012. 44 p.
National Category
Fusion, Plasma and Space Physics Subatomic Physics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-192530 (URN)
Supervisors
Available from: 2013-01-23 Created: 2013-01-22 Last updated: 2016-03-29Bibliographically approved
2. Neutron Emission Spectrometry for Fusion Reactor Diagnosis: Method Development and Data Analysis
Open this publication in new window or tab >>Neutron Emission Spectrometry for Fusion Reactor Diagnosis: Method Development and Data Analysis
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is possible to obtain information about various properties of the fuel ions deuterium (D) and tritium (T) in a fusion plasma by measuring the neutron emission from the plasma. Neutrons are produced in fusion reactions between the fuel ions, which means that the intensity and energy spectrum of the emitted neutrons are related to the densities and velocity distributions of these ions.

This thesis describes different methods for analyzing data from fusion neutron measurements. The main focus is on neutron spectrometry measurements, using data used collected at the tokamak fusion reactor JET in England. Several neutron spectrometers are installed at JET, including the time-of-flight spectrometer TOFOR and the magnetic proton recoil (MPRu) spectrometer.

Part of the work is concerned with the calculation of neutron spectra from given fuel ion distributions. Most fusion reactions of interest – such as the D + T and D + D reactions – have two particles in the final state, but there are also examples where three particles are produced, e.g. in the T + T reaction. Both two- and three-body reactions are considered in this thesis. A method for including the finite Larmor radii of the fuel ions in the spectrum calculation is also developed. This effect was seen to significantly affect the shape of the measured TOFOR spectrum for a plasma scenario utilizing ion cyclotron resonance heating (ICRH) in combination with neutral beam injection (NBI).

Using the capability to calculate neutron spectra, it is possible to set up different parametric models of the neutron emission for various plasma scenarios. In this thesis, such models are used to estimate the fuel ion density in NBI heated plasmas and the fast D distribution in plasmas with ICRH.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 92 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1244
Keyword
fusion, plasma diagnostics, neutron spectrometry, TOFOR, MPRu, tokamak, JET, fast ions, fuel ion density, relativistic kinematics
National Category
Fusion, Plasma and Space Physics Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-247994 (URN)978-91-554-9217-5 (ISBN)
Public defence
2015-05-22, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-04-27 Created: 2015-03-25 Last updated: 2015-07-07

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Eriksson, JacobHellesen, CarlConroy, SeanEricsson, Göran

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