Velocity-space observation regions of high-resolution two-step reaction gamma-ray spectroscopy

Mirko Salewski, M. Nocente, G. Gorini, Asger Schou Jacobsen, V.G. Kiptily, Søren Bang Korsholm, Frank Leipold, Jens Madsen, D. Moseev, Stefan Kragh Nielsen, Jesper Rasmussen, Morten Stejner Pedersen, M. Tardocchi

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High-resolution γ-ray spectroscopy (GRS) measurements resolve spectral shapes of Dopplerbroadened γ-rays. We calculate weight functions describing velocity-space sensitivities of any two-step reaction GRS measurements in magnetized plasmas using the resonant nuclear reaction 9Be(α, nγ)12C as an example. The energy-dependent cross sections of this reaction suggest that GRS is sensitive to alpha particles above about 1.7 MeV and highly sensitive to alpha particles at the resonance energies of the reaction. Here we demonstrate that highresolution two-step reaction GRS measurements are not only selective in energy but also in pitch angle. They can be highly sensitive in particular pitch angle ranges and completely insensitive in others. Moreover, GRS weight functions allow rapid calculation of γ-ray energy spectra from fast-ion distribution functions, additionally revealing how many photons any given alpha-particle velocity-space region contributes to the measurements in each γ-ray energy bin.
Original languageEnglish
JournalNuclear Fusion
Issue number9
Pages (from-to)093029
Number of pages15
Publication statusPublished - 2015


  • Gamma-ray spectroscopy
  • Energetic particles
  • Tokamaks


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