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arxiv: 2602.21256 · v2 · pith:EAOWWS4Lnew · submitted 2026-02-23 · ⚛️ physics.ins-det · nucl-ex

Surrogate neutron-capture studies with fission detection in inverse kinematics at the ESR storage ring

Bogus{\l}aw W{\l}och , Camille Berthelot , Guy Leckenby , Beatriz Jurado , Jerome Pibernat , Manfred Grieser , Jan Glorius , Yuri A. Litvinov
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Laurent Audouin Bertram Blank Lucas B\'egu\'e--Guillou Alex Cobo Zarzuelo Sophia Florence Dellmann Marc Dupuis Oliver Forstner Alexis Francheteau David Freire Fern\'andez Miki Fukutome Mathias Gerbaux J\'er\^ome Giovinazzo Alexandre Gumberidze Andreas Heinz Ana Henriques Regina Hess Indu Jangid Anton Kalinin Wolfram Korten Sergey Litvinov Bernd Lorentz Antonio M. Moro Nikolaos Petridis Ulrich Popp Gregory Potel Diego Ramos Mathieu Roche Mohammad Shahab Sanjari Michele Sguazzin Ragandeep Singh Sidhu Uwe Spillmann Markus Steck Thomas Stoehlker Takayuki Yamaguchi
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Pith reviewed 2026-05-21 12:23 UTC · model grok-4.3

classification ⚛️ physics.ins-det nucl-ex
keywords surrogate reactionsfission detectioninverse kinematicsstorage ringneutron captureheavy nucleiESRdetector performance
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The pith

A new fission-fragment detection system at the ESR storage ring allows simultaneous measurement of gamma-decay, multi-neutron-emission, and fission residues in surrogate neutron-capture studies for the first time.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reports the design and performance of a fission-fragment detector integrated into the NECTAR setup at the ESR heavy-ion storage ring. A stored beam of bare 238U ions at 17.24 MeV/u interacted with a deuterium gas-jet target, populating excited states via deuteron scattering and transfer reactions. The upgraded configuration records gamma-decay residues, multi-neutron-emission residues, and fission fragments together. A sympathetic reader would care because this expands the surrogate-reaction method to include fission as a measurable exit channel in inverse kinematics, where direct neutron measurements on short-lived nuclei remain impractical.

Core claim

The upgraded detector configuration enables, for the first time in a surrogate experiment, the simultaneous detection of gamma-decay residues, multi-neutron-emission residues, and fission fragments. The full setup was tested with a stored beam of bare 238U92+ ions at 17.24 MeV/u interacting with a gas-jet deuterium target through the 238U(d,d') and 238U(d,p) reactions. Geometry, design constraints, and simulation-based efficiency determination for the fission-fragment detectors are described, together with target-like particle identification and beam-like residue spectra.

What carries the argument

Fission-fragment detection system integrated into the NECTAR experimental setup at the ESR, with simulation-based efficiency determination.

Load-bearing premise

The simulation-based efficiency determination for the fission-fragment detectors accurately reflects real-world performance under the experimental conditions of the 238U beam and deuterium gas-jet target.

What would settle it

A direct comparison of measured fission-fragment yields against independent cross-section data for the 238U(d,p) reaction or against high-fidelity Monte Carlo simulations matched to the exact beam energy, target thickness, and detector geometry would confirm or refute the claimed performance.

read the original abstract

The NECTAR (Nuclear rEaCTions At storage Rings) experiment at the ESR heavy-ion storage ring at GSI/FAIR Darmstadt is dedicated to surrogate reaction studies of neutron-induced reactions on heavy nuclei in inverse kinematics. In this work, we report on the implementation and performance of a newly developed fission-fragment detection system integrated into the NECTAR experimental setup. The upgraded detector configuration enables, for the first time in a surrogate experiment, the simultaneous detection ofgamma-decay residues, multi-neutron-emission residues, and fission fragments. The full setup was used for the first time in an experiment where a stored beam of bare 238U92+ ions at 17.24 MeV/u interacted with a gas-jet deuterium target, populating excited 238U and 239U nuclei via the 238U(d,d') and 238U(d,p) reactions. We describe the geometry of the used fission fragment detectors, design constraints, and simulation-based efficiency determination. The target-like particle identification and beam-like residue spectra demonstrating the performance of the complete setup are also shown.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The paper reports the implementation and performance of a new fission-fragment detection system integrated into the NECTAR setup at the ESR storage ring. The upgraded detector configuration enables, for the first time in a surrogate experiment, simultaneous detection of gamma-decay residues, multi-neutron-emission residues, and fission fragments. The work describes the geometry of the fission-fragment detectors, design constraints, and simulation-based efficiency determination, and presents target-like particle identification together with beam-like residue spectra from the first use of the full setup in an experiment with a stored 238U92+ beam at 17.24 MeV/u on a deuterium gas-jet target.

Significance. If the performance claims are substantiated, the result is significant for nuclear instrumentation: it extends surrogate-reaction techniques to include fission detection in inverse kinematics inside a storage ring, opening access to neutron-induced fission and capture data on heavy nuclei that are difficult to obtain by other means. The demonstration of simultaneous multi-channel residue detection is a concrete technical step forward.

major comments (1)
  1. [geometry and design-constraints section] Geometry and design-constraints section: fission-fragment detection efficiency is obtained exclusively from simulation; no in-beam calibration or cross-check against a known fission yield is reported under the actual conditions of the 238U92+ beam at 17.24 MeV/u with the deuterium gas-jet target. Effects such as multiple scattering of high-Z fragments, beam-related backgrounds, or detector non-linearities could therefore cause the real efficiency to deviate from the simulated value, directly affecting the quantitative support for the simultaneous-detection claim.
minor comments (2)
  1. The manuscript would be strengthened by the inclusion of quantitative performance metrics (e.g., measured efficiencies with uncertainties, background rates, and energy resolution) and at least a summary data table or error analysis to move the performance assessment beyond the qualitative spectra shown.
  2. Figure captions and text should explicitly state the beam energy, charge state, and target conditions when presenting the residue spectra so that readers can assess the relevance of the shown data to the claimed performance.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive assessment of the significance of our work and for the constructive comment on the fission-fragment efficiency determination. We address the major comment below.

read point-by-point responses

  1. Referee: Geometry and design-constraints section: fission-fragment detection efficiency is obtained exclusively from simulation; no in-beam calibration or cross-check against a known fission yield is reported under the actual conditions of the 238U92+ beam at 17.24 MeV/u with the deuterium gas-jet target. Effects such as multiple scattering of high-Z fragments, beam-related backgrounds, or detector non-linearities could therefore cause the real efficiency to deviate from the simulated value, directly affecting the quantitative support for the simultaneous-detection claim.

    Authors: We agree that the fission-fragment detection efficiency is determined exclusively from GEANT4 simulations, as stated in the manuscript, and that no in-beam calibration against a known fission yield is reported for the 238U92+ beam at 17.24 MeV/u on the deuterium gas-jet target. This approach was chosen because the reported data represent the first use of the complete NECTAR setup, where fission statistics were limited and dedicated calibration runs were not feasible within the allocated beam time. We will revise the geometry and design-constraints section to include an expanded discussion of potential systematic effects (multiple scattering of high-Z fragments, beam-related backgrounds, and detector response non-linearities) together with quantitative estimates of their influence on the simulated efficiency. This addition will strengthen the quantitative support for the simultaneous multi-channel detection claim without altering the reported results. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental report relies on direct spectra and geometry, not derivations or self-referential fits

full rationale

The manuscript is an instrumentation and performance report for the upgraded NECTAR setup at the ESR. It describes detector geometry, design constraints, and simulation-based efficiency calculations, then presents target-like particle identification and beam-like residue spectra from the 238U + deuterium run. No mathematical derivations, parameter fits, or 'predictions' are claimed that could reduce to the inputs by construction. Efficiency determination is explicitly simulation-based and is not relabeled as an experimental prediction. No self-citation chains, uniqueness theorems, or ansatzes imported from prior author work appear in the load-bearing steps. The central claim of simultaneous detection capability is supported by observed spectra and stated detector geometry rather than tautological modeling. This matches the default expectation for non-circular experimental papers.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard nuclear reaction kinematics, detector response modeling via simulations, and the assumption that the storage-ring beam conditions produce clean surrogate events. No new physical entities or ad-hoc parameters are introduced beyond established experimental techniques.

axioms (2)
  • standard math Standard conservation of energy and momentum in inverse-kinematics reactions at the stated beam energy of 17.24 MeV/u.
    Invoked implicitly when populating excited 238U and 239U states via (d,d') and (d,p) reactions.
  • domain assumption Simulation codes accurately model fission-fragment trajectories and detector response for efficiency calculation.
    Used to determine efficiency; location referenced in the description of the fission-fragment detectors.

pith-pipeline@v0.9.0 · 5936 in / 1443 out tokens · 43057 ms · 2026-05-21T12:23:30.013998+00:00 · methodology

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