Orbit-space sensitivity of two-step reaction gamma-ray spectroscopy

A. Valentini; H. Järleblad; M. Nocente; J. Eriksson; S. Fugazza; O. Hyvärinen; V. Kiptily; D. Moseev; B. C.G. Reman; M. Rud; Antti Snicker; L. Stagner; M. Salewski; JET Contributors

doi:10.1088/1741-4326/ae013d

Orbit-space sensitivity of two-step reaction gamma-ray spectroscopy

A. Valentini
, H. Järleblad
, M. Nocente^*
, J. Eriksson
, S. Fugazza
, O. Hyvärinen
, V. Kiptily
, D. Moseev
, B. C.G. Reman
, M. Rud
, Antti Snicker
, L. Stagner
, M. Salewski
, JET Contributors

^*Corresponding author for this work

BA4511 Fusion energy

Technical University of Denmark (DTU)
University of Milano-Bicocca
University of Milan
Uppsala University
University of Helsinki
United Kingdom Atomic Energy Authority (UKAEA)
Max-Planck-Institut für Plasmaphysik (IPP)
École Royale Militaire
General Atomics

Research output: Contribution to journal › Article › Scientific › peer-review

2 Citations (Scopus)

Abstract

We calculate the orbit-space sensitivity of two-step reaction gamma-ray spectroscopy diagnostics in toroidally symmetric magnetic equilibria, using the reaction between alpha particles and beryllium-9 as an example. To reduce the computational cost, we use analytical solutions obtained by neglecting the velocity of the thermal beryllium. The sensitivity is quantified by weight functions, which we calculate in the alpha-particle orbit space of energy, maximum major radius and pitch at that maximum major radius. Each alpha-particle guiding-center orbit leads to a characteristic gamma-ray spectrum depending on the line-of-sight geometry. We highlight the geometry dependence by repeating the calculation for three different cases, observing significant changes in the sensitivity patterns. Weight functions also allow one to quickly compute forward model problems if spectra from many distribution functions are to be calculated and compared with experimental measurements.

Original language	English
Article number	112001
Journal	Nuclear Fusion
Volume	65
Issue number	11
DOIs	https://doi.org/10.1088/1741-4326/ae013d
Publication status	Published - 1 Nov 2025
MoE publication type	A1 Journal article-refereed

Funding

This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 - EUROfusion). Furthermore, this work was partially funded by the Research Council of Finland project No. 362342. Additionally, A V is supported by the ‘Grants in Aid of Research’ initiative from Sigma Xi, to which we are grateful for the financial support via Grant No. G20240315-8377.

Keywords

alpha particles
energetic ions
fast ion orbits
gamma-ray spectroscopy
orbit space sensitivity
tokamaks

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Cite this

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title = "Orbit-space sensitivity of two-step reaction gamma-ray spectroscopy",

abstract = "We calculate the orbit-space sensitivity of two-step reaction gamma-ray spectroscopy diagnostics in toroidally symmetric magnetic equilibria, using the reaction between alpha particles and beryllium-9 as an example. To reduce the computational cost, we use analytical solutions obtained by neglecting the velocity of the thermal beryllium. The sensitivity is quantified by weight functions, which we calculate in the alpha-particle orbit space of energy, maximum major radius and pitch at that maximum major radius. Each alpha-particle guiding-center orbit leads to a characteristic gamma-ray spectrum depending on the line-of-sight geometry. We highlight the geometry dependence by repeating the calculation for three different cases, observing significant changes in the sensitivity patterns. Weight functions also allow one to quickly compute forward model problems if spectra from many distribution functions are to be calculated and compared with experimental measurements.",

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AU - Valentini, A.

AU - Järleblad, H.

AU - Nocente, M.

AU - Eriksson, J.

AU - Fugazza, S.

AU - Hyvärinen, O.

AU - Kiptily, V.

AU - Moseev, D.

AU - Reman, B. C.G.

AU - Rud, M.

AU - Snicker, Antti

AU - Stagner, L.

AU - Salewski, M.

AU - JET Contributors

PY - 2025/11/1

Y1 - 2025/11/1

N2 - We calculate the orbit-space sensitivity of two-step reaction gamma-ray spectroscopy diagnostics in toroidally symmetric magnetic equilibria, using the reaction between alpha particles and beryllium-9 as an example. To reduce the computational cost, we use analytical solutions obtained by neglecting the velocity of the thermal beryllium. The sensitivity is quantified by weight functions, which we calculate in the alpha-particle orbit space of energy, maximum major radius and pitch at that maximum major radius. Each alpha-particle guiding-center orbit leads to a characteristic gamma-ray spectrum depending on the line-of-sight geometry. We highlight the geometry dependence by repeating the calculation for three different cases, observing significant changes in the sensitivity patterns. Weight functions also allow one to quickly compute forward model problems if spectra from many distribution functions are to be calculated and compared with experimental measurements.

AB - We calculate the orbit-space sensitivity of two-step reaction gamma-ray spectroscopy diagnostics in toroidally symmetric magnetic equilibria, using the reaction between alpha particles and beryllium-9 as an example. To reduce the computational cost, we use analytical solutions obtained by neglecting the velocity of the thermal beryllium. The sensitivity is quantified by weight functions, which we calculate in the alpha-particle orbit space of energy, maximum major radius and pitch at that maximum major radius. Each alpha-particle guiding-center orbit leads to a characteristic gamma-ray spectrum depending on the line-of-sight geometry. We highlight the geometry dependence by repeating the calculation for three different cases, observing significant changes in the sensitivity patterns. Weight functions also allow one to quickly compute forward model problems if spectra from many distribution functions are to be calculated and compared with experimental measurements.

KW - alpha particles

KW - energetic ions

KW - fast ion orbits

KW - gamma-ray spectroscopy

KW - orbit space sensitivity

KW - tokamaks

UR - https://www.scopus.com/pages/publications/105017502643

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DO - 10.1088/1741-4326/ae013d

M3 - Article

AN - SCOPUS:105017502643

SN - 0029-5515

VL - 65

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 11

M1 - 112001

ER -

Orbit-space sensitivity of two-step reaction gamma-ray spectroscopy

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