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Forward fitting of experimental data from a NE213 neutron detector installed with the magnetic proton recoil upgraded spectrometer 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.ORCID iD: 0000-0002-0892-3358
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
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2014 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E123-Article in journal (Refereed) Published
Abstract [en]

In this paper, we present the results obtained from the data analysis of neutron spectra measured with a NE213 liquid scintillator at JET. We calculated the neutron response matrix of the instrument combining MCNPX simulations, a generic proton light output function measured with another detector and the fit of data from ohmic pulses. For the analysis, we selected a set of pulses with neutral beam injection heating (NBI) only and we applied a forward fitting procedure of modeled spectral components to extract the fraction of thermal neutron emission. The results showed the same trend of the ones obtained with the dedicated spectrometer TOFOR, even though the values from the NE213 analysis were systematically higher. This discrepancy is probably due to the different lines of sight of the two spectrometers (tangential for the NE213, vertical for TOFOR). The uncertainties on the thermal fraction estimates were from 4 to 7 times higher than the ones from the TOFOR analysis.

Place, publisher, year, edition, pages
2014. Vol. 85, no 11, p. 11E123-
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-240136DOI: 10.1063/1.4895565ISI: 000345646000143PubMedID: 25430302OAI: oai:DiVA.org:uu-240136DiVA, id: diva2:776642
Available from: 2015-01-07 Created: 2015-01-05 Last updated: 2018-04-23
In thesis
1. Neutron emission spectroscopy of fusion plasmas with a NE213 liquid scintillator at JET
Open this publication in new window or tab >>Neutron emission spectroscopy of fusion plasmas with a NE213 liquid scintillator at JET
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Neutron diagnostics will play a fundamental role in future fusion plasma machines,where the harsh environment will make the use of many other type of diagnos-tics practically impossible. Complex techniques to measure the neutron spectrumemitted from tokamk plasmas have been developed over the years, producing stateof the art neutron spectrometers. However, recently compact neutron spectrom-eters have been gaining the interest of the research community. They are muchsimpler to operate and maintain, have lower cost and they can be employed in thechannels of a neutron camera, providing profile measurements. The drawbacks arethat they have a worse resolution and a response to neutrons that is not optimalfor spectroscopy.The goal of the work presented in this thesis is to estimate to which extenta compact detector such as a NE213 liquid scintillator can be used to performneutron emission spectroscopy analysis.The detector used for this study was installed in the back of the MPRu spec-trometer at JET in 2012. The characterization of the response of the detector wasdone using a combination of MCNPX simulations and real measurements. Thedata analysis was performed using the forward fitting approach: a model of theneutron spectrum is produced, then folded with the response of the detector andfinally compared with the data. Two types of plasma scenarios were analyzed, onewith NBI heating only, and another with NBI and third harmonic radio-frequencyheating. In both cases the TOFOR spectrometer was used as a reference to esti-mate the parameters in the model of the neutron spectrum.The results are promising and suggest that neutron spectroscopy can be per-formed with NE213 scintillators although the quality of the results, as given byperformance indicators such as uncertainties, is much lower than the performanceof high resolution spectrometers.

Place, publisher, year, edition, pages
Uppsala: Uppsala University, 2015
Keywords
NE213, neutron spectroscopy, liquid scintillator, nuclear, fusion, plasma
National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-291506 (URN)
Presentation
2015-05-18, 15:15 (English)
Opponent
Supervisors
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2016-05-09Bibliographically approved
2. Liquid scintillators as neutron diagnostic tools for fusion plasmas: System characterization and data analysis
Open this publication in new window or tab >>Liquid scintillators as neutron diagnostic tools for fusion plasmas: System characterization and data analysis
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The neutrons produced in fusion devices carry information about various properties of the ions that are reacting in the machine. Measurements of the neutron flux and energy distribution can therefore be used to study the behaviour of the plasma ions under different experimental conditions.

Several neutron detection techniques are available, each having advantages and disadvantages compared to the others. In this thesis we study neutron measurements performed with NE213 liquid scintillators. One advantage of NE213s compared to other neutron detection techniques is that they are simple to use, small and cheap. On the other hand, their response to neutrons makes the extraction of information about the neutron energy less precise.

In the thesis we present the development of methods for the characterization and the data analysis of NE213 detectors. The work was performed using two instruments installed at the Joint European Torus (JET) tokamak in the UK: the “Afterburner” detector, which is an NE213 installed on a tangential line of sight, and the neutron camera, which is a system composed of 19 NE213 detectors installed on different lines of sight (10 horizontal and 9 vertical).The analysis of data from the Afterburner detector was focused on resolving different features of the neutron energy spectra which are related to different properties of the ion velocity distribution.

The analysis of data from the neutron camera was directed towards the investigation of the spatial distribution of ions in the plasma. However, the individual characterization of the camera detectors allowed the inclusion of information about the energy distribution of the ions in the analysis.

The outcomes of the studies performed indicate that the methods developed give reliable results and can therefore be applied to extract information about the plasma ions. In particular, the possibility of performing neutron emission spectroscopy analysis in each line of sight of a neutron camera is of great value for future studies.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1646
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-345983 (URN)978-91-513-0275-1 (ISBN)
Public defence
2018-05-04, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2018-04-11 Created: 2018-03-13 Last updated: 2018-04-11

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Binda, FedericoEricsson, GöranEriksson, JacobHellesen, CarlConroy, SeanSundén, Erik Andersson

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