Fast-ion orbit sensitivity of neutron and gamma-ray diagnostics for one-step fusion reactions

H. Järleblad*, L. Stagner, M. Salewski, J. Eriksson, M. Nocente, J. Rasmussen, Štancar, Ye O. Kazakov, B. Simmendefeldt

*Corresponding author for this work

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Abstract

Fast ions in the MeV-range can be diagnosed by neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS). In this work, we present orbit weight functions for one-step fusion reactions, using NES and GRS diagnostics on perpendicular and oblique lines-of-sight (LOS) at Joint European Torus (JET) as examples. The orbit weight functions allow us to express the sensitivities of the diagnostics in terms of fast-ion (FI) orbits and can be used to swiftly reproduce synthetic signals that have been computed by established codes. For diagnostically relevant neutron energies for the D(D, n)3He reaction, the orbit sensitivities of the NES diagnostics follow a predictable pattern. As the neutron energy of interest increases, the pattern shifts upwards in FI energy. For the GRS diagnostic and the T(p, 3)4He reaction, the orbit sensitivity is shown to be qualitatively different for red-shifted, blue-shifted and nominal gamma birth energies. Finally, we demonstrate how orbit weight functions can be used to decompose diagnostic signals into the contributions from different orbit types. For a TRANSP simulation of the JET discharge (a three-ion ICRF scenario) considered in this work, the NES signals for both the perpendicular and oblique LOS are shown to originate mostly from co-passing orbits. In addition, a significant fraction of the NES signal for the oblique LOS is shown to originate from stagnation orbits.

Original languageEnglish
Article number112005
JournalNuclear Fusion
Volume62
Issue number11
Number of pages15
ISSN0029-5515
DOIs
Publication statusPublished - 2022

Keywords

  • Energetic particle diagnostics
  • Energetic particle physics
  • Gamma-ray emission
  • Neutron emission
  • One-step fusion reactions
  • Plasma diagnostics
  • Tomography

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