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Analysis of the fast ion tails observed in the NE213pulse height specta measured during third harmonicradio-frequency heating experiments at JET
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. (Nuclear Fusion)
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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(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper we investigate the possibility of using a NE213 liquid scintillator as aneutron spectrometer to diagnose the fast ion tails produced in experiments with 3rd harmonicradio-frequency heating.We discuss mainly the instrumental effects that need to be considered and corrected for in orderto obtain a good agreement between measured data and models: gain drift, pile-up, impact of theassumption of a standard proton light yield function. We also address problems related to thepresence of triton burn-up events in the spectrum.The expected ion distribution is obtained from a simple 1D Fokker-Planck model. The parametersof the model are estimated using the data collected by the TOFOR neutron spectrometer.The agreement between the data and the model is good and it is possible to make a clear distinctionbetween discharges that had different electron densities and thus different cut-off energies. Wecan conclude that NE213 scintillators can provide useful spectroscopic information for this kind ofexperiments.

National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:uu:diva-292741OAI: oai:DiVA.org:uu-292741DiVA: diva2:926550
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2016-07-18Bibliographically approved
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
Keyword
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

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Binda, FedericoEriksson, JacobEricsson, GöranHellesen, CarlCecconello, MarcoAndersson Sundén, Erik
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