| 1. |
- Kiptily, V., et al.
(author)
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Doppler broadening of gamma ray lines and fast ion distribution in JET plasmas
- 2010
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 50:8, s. 084001-
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Journal article (peer-reviewed)abstract
- The Doppler broadening of individual γ-ray lines was measured with a high purity germanium detector in JET plasma experiments. High-resolution γ-ray spectrometry of nuclear reactions between energetic D, 3 He and 4 He ions accelerated by ion cyclotron resonance heating and main plasma impurities such as carbon and beryllium has been used. The nuclear reactions giving rise to γ-rays have been identified and an effective temperature of the heated ions has been obtained in JET discharges. This technique could be used for fast ion and fusion alpha-particle studies in ITER.
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| 2. |
- Gatu Johnson, Maria, et al.
(author)
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Modelling and TOFOR measurements of scattered neutrons at JET
- 2010
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In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 52:8, s. 085002-
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Journal article (peer-reviewed)abstract
- In this paper, the scattered and direct neutron fluxes in the line of sight (LOS) of the TOFOR neutron spectrometer at JET are simulated and the simulations compared with measurement results. The Monte Carlo code MCNPX is used in the simulations, with a vessel material composition obtained from the JET drawing office and neutron emission profiles calculated from TRANSP simulations of beam ion density profiles. The MCNPX simulations show that the material composition of the scattering wall has a large effect on the shape of the scattered neutron spectrum. Neutron source profile shapes as well as radial and vertical source displacements in the TOFOR LOS are shown to only marginally affect the scatter, while having a larger impact on the direct neutron flux. A matrix of simulated scatter spectra for mono-energetic source neutrons is created which is folded with an approximation of the source spectrum for each JET pulse studied to obtain a scatter component for use in the data analysis. The scatter components thus obtained are shown to describe the measured data. It is also demonstrated that the scattered flux is approximately constant relative to the total neutron yield as measured with the JET fission chambers, while there is a larger spread in the direct flux, consistent with simulations. The simulated effect on the integrated scattered/direct ratio of an increase with movements outward along the radial direction and a drop at higher values of the vertical plasma position is also reproduced in the measurements. Finally, the quantitative agreement found in scatter/direct ratios between simulations (0.185 ± 0.005) and measurements (0.187 ± 0.050) serves as a solid benchmark of the MCNPX model used.
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| 3. |
- Nocente, M., et al.
(author)
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High-resolution gamma ray spectroscopy measurements of the fast ion energy distribution in JET He-4 plasmas
- 2012
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 52:6, s. 063009-
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Journal article (peer-reviewed)abstract
- High-resolution gamma-ray measurements were carried out on the Joint European Torus (JET) in an experiment aimed at accelerating He-4 ions in the MeV range by coupling third harmonic radio frequency heating to an injected He-4 beam. For the first time, Doppler broadening of gamma-ray peaks from the C-12(d, p gamma)C-13 and Be-9(alpha, n gamma)C-12 reactions was observed and interpreted with dedicated Monte Carlo codes based on the detailed nuclear physics of the processes. Information on the confined He-4 and deuteron energy distribution was inferred, and confined He-4 ions with energies as high as 6 MeV were assessed. A signature of MHD activity in gamma-ray traces was also detected. The reported results have a bearing on diagnostics for fast ions in the MeV range in next step fusion devices.
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