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Triton burn-up neutron emission in JET low current plasmas
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Neutron Research, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Neutron Research, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Neutron Research, Applied Nuclear Physics.
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2008 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 41, no 11, 115208- p.Article in journal (Refereed) Published
Abstract [en]

The 14 MeV neutron emission from JET deuterium discharges is analysed on the basis of the information on all neutron diagnostics available on JET. This emission is due to the d + t → α + n reaction, mainly, the triton burn-up process, and is used to determine the fast triton confinement. A simplified model for triton burn-up neutron emission has been used and provides an adequate description of the 14 MeV emission. First orbit triton losses are found to amount to 50%, 20% and 10% at Ip = 1 MA, 2 MA and 3 MA, respectively. Neutron emission spectroscopy measurements with the magnetic proton recoil neutron spectrometer have detected a contribution to the 14 MeV emission due to residual tritium. For the selected (low impurity) discharges analysed in this paper 15% of the 14 MeV emission comes from the residual tritium reactions. It is also found that the residual tritium concentration tends to increase with increasing impurity content.

Place, publisher, year, edition, pages
2008. Vol. 41, no 11, 115208- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97579DOI: 10.1088/0022-3727/41/11/115208OAI: oai:DiVA.org:uu-97579DiVA: diva2:172577
Available from: 2008-10-03 Created: 2008-10-03 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Neutron Spectroscopy: Instrumentation and Methods for Fusion Plasmas
Open this publication in new window or tab >>Neutron Spectroscopy: Instrumentation and Methods for Fusion Plasmas
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When the heavy hydrogen isotopes deuterium (D) and tritium (T) undergo nuclear fusion large amounts of energy are released. At the Joint European Torus (JET) research is performed on how to harvest this energy. Two of the most important fusion reactions, d+d→3He+n (En = 2.5 MeV) and d+t→4He+n (En = 14 MeV), produce neutrons. This thesis investigates how measurements of these neutrons can provide information on the fusion performance.

The Magnetic Proton Recoil (MPR) neutron spectrometer has operated at JET since 1996. The spectrometer was designed to provide measurements on the 14 MeV neutron emission in DT operation, thereby conveying information on the state of the fuel ions. However, a majority of today’s fusion experiments are performed with pure D fuel. Under such conditions, the measurements with the MPR were severely hampered due to interfering background. This prompted an upgrade of the instrument. The upgrade, described in this thesis, included a new focal plane detector, a phoswich scintillator array, and new data acquisition electronics, based on transient recorder cards. This combination allows for pulse shape discrimination techniques to be applied and a signal to background of 5/1 has been achieved in measurements of the 2.5-MeV neutrons in D experiments. The upgrade also includes a new control and monitoring system, which enables the monitoring and correction of gain variations in the spectrometer’s photo multiplier tubes. Such corrections are vital for obtaining good data quality.

In addition, this thesis describes a new method for determining the total neutron yield and hence the fusion power by using a MPR spectrometer in combination with a neutron emission profile monitor. The system has been operated at JET both during DT and D experiments. It is found that the systematic uncertainties are considerably lower (≈6 %) than for traditional systems. For a dedicated system designed for the next generation fusion experiments, i.e, ITER, uncertainties of 4 % could be attained.

Neutron spectroscopy can also be an important tool for determining the neutron emission from residual tritium in D plasmas. This information is combined with other measurements at JET in order to determine the confinement of the 1 MeV tritons from the d+d→t+p reactions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 556
Keyword
Neutron spectroscopy, plasma diagnostics, fusion power, fusion, plasma heating, MPRu, JET, triton burn-up, ITER, neutron yield, calibration
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-9296 (URN)978-91-554-7292-4 (ISBN)
Public defence
2008-10-24, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15
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Available from: 2008-10-03 Created: 2008-10-03 Last updated: 2011-01-12Bibliographically approved

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Sjöstrand, HenrikConroy, SeanEricsson, GöranHjalmarsson, AndersKällne, JanWeiszflog, Matthias

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