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arxiv: 2604.19180 · v1 · submitted 2026-04-21 · ⚛️ nucl-ex · nucl-th

Recognition: unknown

Proton induced reactions on 118Sn target at energies up to 18 MeV

A. Aprahamian, A. Manukyan, A. R. Balabekyan, G. H. Hovhannisyan, G.V. Martirosyan, N.S. Gharibyan, R.K. Dallakyan, S.V. Gaginyan, T. M. Bakhshiyan

Pith reviewed 2026-05-10 01:41 UTC · model grok-4.3

classification ⚛️ nucl-ex nucl-th
keywords proton-induced reactionstin-118nuclear cross sectionsexcitation functionscomposite particle emissionstacked-foil activationnuclear reaction models
0
0 comments X

The pith

New cross sections for proton reactions on 118Sn are measured, with first reports for two channels showing discrepancies in models of composite particle emission.

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

The paper measures the excitation functions for proton-induced reactions on an enriched 118Sn target at energies up to 18 MeV using the stacked-foil activation technique. It provides the first reported cross sections for the 118Sn(p,x)117mSn and 118Sn(p,α)115mIn reactions. Where previous data exist, the new measurements agree with them. However, comparisons with theoretical calculations reveal discrepancies specifically for reactions that emit composite particles such as alpha particles and deuterons. This indicates that nuclear models need further development to accurately describe these more complex emission processes at lower energies.

Core claim

The central discovery is the experimental determination of excitation functions for four proton-induced reactions on 118Sn, including the first data for channels producing 117mSn and 115mIn, along with the observation that theoretical predictions differ in the composite-particle emission channels.

What carries the argument

The stacked-foil activation technique, in which thin target foils are stacked to allow measurement of reaction yields at progressively lower energies through gamma-ray spectroscopy after irradiation.

If this is right

  • The measured cross sections can serve as benchmarks for improving nuclear reaction models.
  • Discrepancies suggest that models for composite particle emission require refinements at proton energies below 18 MeV.
  • Simple two-nucleon emission channels are adequately described by current models, while more complex ones are not.
  • These results validate the measurement approach for other similar reactions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the discrepancies hold, they could guide refinements in theoretical codes for alpha emission in proton reactions on nearby nuclei.
  • Measurements on other tin isotopes using the same method might show whether the model issues are systematic.
  • The technique's success here supports its application to additional light-particle induced reactions lacking data.

Load-bearing premise

The stacked-foil activation technique accurately isolates individual reaction channels by correctly accounting for energy degradation in the foils and detecting specific gamma rays without significant interference from impurities or overlapping activities.

What would settle it

An independent measurement of the 118Sn(p,α)115mIn cross section using direct alpha particle detection that agrees with theoretical predictions rather than the reported values would falsify the discrepancy.

Figures

Figures reproduced from arXiv: 2604.19180 by A. Aprahamian, A. Manukyan, A. R. Balabekyan, G. H. Hovhannisyan, G.V. Martirosyan, N.S. Gharibyan, R.K. Dallakyan, S.V. Gaginyan, T. M. Bakhshiyan.

Figure 3
Figure 3. Figure 3: The energy distributions of protons within the tin layer of the stacked target. Based on SRIM calculations, the values of the average energy 𝐸𝑎𝑣 were determined according to equation (2) for each layer. The effective energy 𝐸𝑒𝑓𝑓 for each layer was obtained by considering the proton energy distribution within the foil. It was calculated according to equation (4), where 𝐷(𝐸,𝑡0) is the normalized proton energ… view at source ↗
Figure 4
Figure 4. Figure 4: Dependence of the proton energy on the target number in the stack. Target number 1 corresponds to the first monitor foil; the subsequent targets alternate between tin and copper foils. Red dots represent the experimentally determined energies, black squares correspond to the SRIM-based calculated average energies 𝐸𝑎𝑣, and blue stars indicate the SRIM-based effective energies 𝐸𝑒𝑓𝑓 (see the text). The error … view at source ↗
read the original abstract

Proton-induced reactions on enriched 118Sn up to 18 MeV have been investigated. Using the stacked-foil activation technique, the excitation functions of the reactions 118Sn(p,n)118Sb, 118Sn(p,2n)117Sb, 118Sn(p,{\alpha})115mIn, and 118Sn(p,x)117mSn were measured. The available experimental data show good agreement with our measurements. The cross sections for the 118Sn(p,x)117mSn and 118Sn(p,{\alpha})115mIn reactions are reported for the first time. The measured cross sections were compared not only with previously published experimental results, but also with theoretical predictions from the TENDL-2023 (TALYS-based evaluated nuclear data library), TENDL-2025 and JENDL-5 (Japanese Evaluated Nuclear Data Library) libraries. Discrepancies between experimental and theoretical data were observed for reactions involving composite-particle emission, such as alpha particles and deuterons. These differences suggest that while current models adequately describe simple two-nucleon emission channels, further refinements are needed, particularly for modeling composite-particle emission at lower proton energies.

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

3 major / 2 minor

Summary. The manuscript reports measurements of proton-induced reaction cross sections on enriched 118Sn up to 18 MeV using the stacked-foil activation technique. Excitation functions are given for 118Sn(p,n)118Sb, 118Sn(p,2n)117Sb, 118Sn(p,α)115mIn, and 118Sn(p,x)117mSn, with the latter two presented for the first time. Results agree with prior data where available and are compared to TENDL-2023, TENDL-2025, and JENDL-5 predictions, with noted discrepancies for composite-particle emission channels.

Significance. If the measurements hold, the new data on 117mSn and 115mIn production channels would fill gaps in evaluated libraries and support refinements to TALYS-based models for composite-particle emission at low energies. The work supplies direct experimental benchmarks against independent libraries, which is valuable for nuclear data applications such as medical isotope production.

major comments (3)
  1. [Experimental procedure] Experimental procedure and data analysis sections: the manuscript provides no explicit uncertainty budget or propagation details for the reported cross sections (e.g., contributions from beam current monitoring, target thickness, gamma-ray efficiency, or energy degradation in the stack). This is load-bearing for the central claim of first-time measurements of 118Sn(p,x)117mSn and 118Sn(p,α)115mIn.
  2. [Data analysis] Data analysis: no quantification or discussion of possible interfering gamma-ray activities from target impurities, trace isotopes, or overlapping reaction channels that could feed the same residuals (117mSn or 115mIn) in the stacked-foil geometry. The skeptic's concern about channel isolation is not addressed, undermining the reported discrepancies with TENDL/JENDL for composite-particle channels.
  3. [Results] Results section: the claim of good agreement with prior data is stated without tabulated comparison values or statistical measures (e.g., χ² or deviation plots), making it difficult to evaluate consistency for the two new excitation functions.
minor comments (2)
  1. [Abstract] The reaction notation 118Sn(p,x)117mSn should be clarified to specify the dominant contributing channels at these energies.
  2. [Figures] Figure captions for excitation functions could include the specific gamma lines used for activity determination and any coincidence requirements.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed comments. These have helped us identify areas where the manuscript can be strengthened for clarity and rigor. We address each major comment point by point below and will revise the manuscript accordingly.

read point-by-point responses

  1. Referee: [Experimental procedure] Experimental procedure and data analysis sections: the manuscript provides no explicit uncertainty budget or propagation details for the reported cross sections (e.g., contributions from beam current monitoring, target thickness, gamma-ray efficiency, or energy degradation in the stack). This is load-bearing for the central claim of first-time measurements of 118Sn(p,x)117mSn and 118Sn(p,α)115mIn.

    Authors: We acknowledge that an explicit, consolidated uncertainty budget with propagation details was not included in the submitted manuscript. In the revised version, we will add a dedicated subsection (or table) in the Experimental procedure or Data analysis section that quantifies and propagates all major uncertainty sources: beam current (via Faraday cup and monitor reactions), target thickness (weighing plus alpha-particle transmission), gamma-ray efficiency (calibrated with standard sources and geometry corrections), energy degradation (SRIM calculations for the stack), and counting statistics. This will directly support the reliability of the new data for the 118Sn(p,x)117mSn and 118Sn(p,α)115mIn channels. revision: yes

  2. Referee: [Data analysis] Data analysis: no quantification or discussion of possible interfering gamma-ray activities from target impurities, trace isotopes, or overlapping reaction channels that could feed the same residuals (117mSn or 115mIn) in the stacked-foil geometry. The skeptic's concern about channel isolation is not addressed, undermining the reported discrepancies with TENDL/JENDL for composite-particle channels.

    Authors: We agree that explicit discussion of potential interferences is necessary to substantiate channel isolation, especially for the new composite-particle channels. In the revised manuscript, we will add a paragraph in the Data analysis section that quantifies upper limits on contributions from target impurities (using the stated enrichment level of 118Sn and known cross sections for other Sn isotopes), trace activities, and any overlapping channels that could populate 117mSn or 115mIn. This will include checks via multiple gamma lines where possible and will be used to confirm that the observed discrepancies with TENDL-2023/2025 and JENDL-5 for alpha and deuteron emission are not artifacts of contamination. revision: yes

  3. Referee: [Results] Results section: the claim of good agreement with prior data is stated without tabulated comparison values or statistical measures (e.g., χ² or deviation plots), making it difficult to evaluate consistency for the two new excitation functions.

    Authors: We accept that the statement of agreement with prior data lacks quantitative support in the current text. The revised Results section will include a table listing our measured cross sections alongside previously published values (for the (p,n) and (p,2n) channels) with percentage deviations. For the two new channels (118Sn(p,x)117mSn and 118Sn(p,α)115mIn), we will explicitly note the absence of prior data. We will also add a supplementary figure or table providing average deviations and, where appropriate, χ²-like metrics to allow readers to assess consistency with literature and the magnitude of discrepancies with the theoretical libraries. revision: yes

Circularity Check

0 steps flagged

No circularity: pure experimental cross-section measurements compared to independent libraries

full rationale

The paper reports direct measurements of excitation functions via stacked-foil activation on enriched 118Sn, with new data for two channels presented for the first time and compared to external evaluated libraries (TENDL-2023/2025, JENDL-5). No theoretical derivation, parameter fitting to the new results, self-citation of uniqueness theorems, or ansatz smuggling occurs. The central claims rest on experimental technique and external benchmarks, remaining self-contained without reduction to the paper's own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the accuracy of the stacked-foil technique and the independence of the evaluated libraries used for comparison. No free parameters are fitted to the new data.

axioms (1)
  • domain assumption The stacked-foil activation technique combined with gamma-ray spectroscopy yields reliable excitation functions when energy loss and activity corrections are applied.
    Standard assumption in nuclear reaction experiments; invoked implicitly when reporting measured cross sections.

pith-pipeline@v0.9.0 · 5571 in / 1157 out tokens · 37797 ms · 2026-05-10T01:41:14.046019+00:00 · methodology

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Reference graph

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