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Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET
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2015 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 12, 123026Article in journal (Refereed) PublishedText
Abstract [en]

Observations made in a JET experiment aimed at accelerating deuterons to the MeV range by third harmonic radio-frequency (RF) heating coupled into a deuterium beam are reported. Measurements are based on a set of advanced neutron and gamma-ray spectrometers that, for the first time, observe the plasma simultaneously along vertical and oblique lines of sight. Parameters of the fast ion energy distribution, such as the high energy cut-off of the deuteron distribution function and the RF coupling constant, are determined from data within a uniform analysis framework for neutron and gamma-ray spectroscopy based on a one-dimensional model and by a consistency check among the individual measurement techniques. A systematic difference is seen between the two lines of sight and is interpreted to originate from the sensitivity of the oblique detectors to the pitch-angle structure of the distribution around the resonance, which is not correctly portrayed within the adopted one dimensional model. A framework to calculate neutron and gamma-ray emission from a spatially resolved, two-dimensional deuteron distribution specified by energy/pitch is thus developed and used for a first comparison with predictions from ab initio models of RF heating at multiple harmonics. The results presented in this paper are of relevance for the development of advanced diagnostic techniques for MeV range ions in high performance fusion plasmas, with applications to the experimental validation of RF heating codes and, more generally, to studies of the energy distribution of ions in the MeV range in high performance deuterium and deuterium-tritium plasmas.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015. Vol. 55, no 12, 123026
Keyword [en]
neutron spectroscopy, gamma-ray spectroscopy, fast ions, MeV range
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-180510DOI: 10.1088/0029-5515/55/12/123026ISI: 000366534500028ScopusID: 2-s2.0-84948687626OAI: diva2:895032

QC 20160118

Available from: 2016-01-18 Created: 2016-01-14 Last updated: 2016-01-18Bibliographically approved

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Hellsten, TorbjörnJohnson, Thomas
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