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REVIEW 1 major objections 7 minor 32 references

Gamma Backgrounds for Experiments at the High Flux Isotope Reactor

T0 review · 1 major / 7 minor · reviewed 2026-07-08 · glm-5.2

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Pith's one-line read Gamma Map of Reactor Hall Validated for Future Neutrino Experiments

desk verdict Solid background characterization for HFIR; the unfolded flux spectra are useful but only shape-validated, not absolute-flux-validated. read the letter →

arxiv 2607.05834 v1 pith:FTOQR4PG submitted 2026-07-07 hep-ex nucl-ex

M. Andriamirado , A. B. Balantekin , C. Baldenegro , C. D. Bass , O. Benevides Rodrigues , E. P. Bernard , N. S. Bowden , C. D. Bryan
show 48 more authors
R. Carr T. Classen A. J. Conant N. Craft G. Deichert A. Delgado M. J. Dolinski A. Erickson M. D. Fuller A. Galindo-Uribarri S. Ghosh C. E. Gilbert D. C. Glasgow S. Gokhale C. G. Grant B. T. Hackett S. Hans A. B. Hansell T. E. Haugen K. M. Heeger B. A. Heffron A. Irani D. E. Jaffe J. Koblanski C. E. Lane B. R. Littlejohn A. Lozano Sanchez X. Lu F. Machado J. Maricic M. P. Mendenhall A. M. Meyer R. Milincic P. E. Mueller H. P. Mumm R. Neilson J. R. Newby D. Norcini N. Patel C. Roca E. Romero-Romero R. Rosero D. Venegas-Vargas B. White J. Wilhelmi M. Yeh C. Zhang X. Zhang
This is my paper
classification hep-exnucl-ex PACS 29.30.Kv28.41.Qb29.40.Wk
keywords gammaspectroscopyreactorbackgroundsHPGedetectorRichardson-LucyunfoldingGeant4simulationHFIRPROSPECTCEvNS
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper deploys a high-purity germanium detector at the HFIR reactor experiment hall to measure the energy, spatial distribution, and temporal variation of gamma radiation backgrounds. The authors use Geant4 detector-response simulations and Richardson-Lucy deconvolution to unfold measured spectra into quantitative incident gamma flux models at six key locations, bracketed by two limiting assumptions about the angular illumination (isotropic vs. front-face). They identify the dominant background sources: gammas from the reactor structure (neutron capture on steel, aluminum, beryllium), the HB4 beamline cold-source shielding (titanium capture lines), and residual contamination at the Materials Irradiation Facility. They confirm that gamma rates scale linearly with reactor power and that the lead shield wall reduces backgrounds by factors of 5–10 in the PROSPECT region, with even stronger suppression (60–80-fold) at multi-MeV energies. A concentric 'Russian Doll' shield study shows that with approximately 23 cm of additional water-brick shielding, reactor-related backgrounds in the 30–60 keV range approach within a factor of 2–4 of ambient (cosmic and material radioactivity) levels, suggesting the site is approaching suitability for CEvNS detection. The unfolded flux models are validated against PROSPECT liquid-scintillator data, showing spectral-shape agreement to better than 10% from 200 keV to 1 MeV, within about 25% from 1–6 MeV, and within a factor of 2 from 6–11.5 MeV. The authors also propose the 11.39 MeV neutron-capture line on 59Ni as an in-situ energy calibration feature for future experiments lacking internal calibration tubes.

What carries the argument

Richardson-Lucy unfolding; Geant4 detector-response simulation with fitted dead-layer parameters; two limiting angular-illumination assumptions (isotropic and front-face) that bracket the unfolded flux; high-purity germanium (HPGe) detector in lead collimator and Russian Doll shielding configurations; PROSPECT liquid-scintillator Monte Carlo (PG4) for cross-validation

What would settle it

If the PROSPECT detector data showed spectral-shape disagreement with the unfolded flux models exceeding the stated bounds (10% below 1 MeV, 25% at 1–6 MeV, factor of 2 at 6–11.5 MeV) across multiple segments and locations, the utility of the unfolded source terms for future experimental planning would be undermined.

Watch

Extended reading notes

Core claim

The central deliverable is a set of unfolded, quantitative gamma flux spectra at six locations in the HFIR Experiment Hall, validated against an independent detector (PROSPECT) and packaged as source terms for future experimental planning. The paper establishes that these models reproduce the gamma spectral shape observed in PROSPECT to within known, bounded uncertainties across a wide energy range (200 keV to 11.5 MeV), and that the dominant systematic uncertainty comes not from the unfolding algorithm but from the detector-response simulation's assumed illumination geometry and incomplete modeling of detector-plus-shield interactions. A secondary finding is that the Russian Doll shielding,

Load-bearing premise

The Geant4 detector-response model, with dead-layer thicknesses fitted only up to 1332 keV and a spherical charge-distribution approximation that omits charge-trapping non-linearity, is assumed to accurately reproduce the migration matrix used for unfolding gamma spectra up to 12 MeV.

Editorial extensions

If this is right

  • Future neutrino experiments at HFIR can use the tabulated unfolded flux spectra as direct input to background simulations, reducing the need for dedicated pre-deployment gamma survey campaigns.
  • The 11.39 MeV 59Ni neutron-capture line offers a reactor-correlated, high-energy calibration point for detectors that cannot accommodate internal source tubes, extending calibration reach well above standard source energies.
  • The finding that reactor-related backgrounds approach ambient levels with ~23 cm of water shielding in the CEvNS-relevant 30–60 keV range provides a concrete shielding design target for next-generation reactor experiments.
  • The demonstrated sensitivity of unfolded low-energy flux to the assumed angular illumination model signals that future gamma-characterization campaigns at reactors should incorporate multi-directional or rotationally sampled measurements to break the isotropic/front-face degeneracy.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The factor-of-2 discrepancy at 6–11.5 MeV between the unfolded flux model and PROSPECT data likely stems from the lack of high-energy efficiency calibration of the HPGe detector (calibrated only to 1332 keV), suggesting that a dedicated high-energy gamma-source calibration would substantially tighten the model's upper-energy fidelity.
  • The unexpected 113Cd line in the Russian Doll spectrum, modeled as ~15% natural cadmium contamination in the tin layer, implies that shielding-material assay prior to deployment could prevent unforeseen background lines in future low-background detector assemblies.
  • The persistent low-energy suppression in the front-face unfold at the MIF position, attributed to detector-plus-shield response mismodeling, suggests that incorporating charge-trapping non-linearity and a more realistic angular distribution (beyond the two-limit bracket) would be necessary to push the flux model below the current ~10% shape-agreement level.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

1 major / 7 minor

Summary. This paper reports a systematic gamma-background characterization of the HFIR Experiment Hall using a 1 kg HPGe detector deployed in two configurations: a movable lead collimator for spatial surveying and a concentric 'Russian Doll' shield for low-energy background studies. The measurements cover energies from 30 keV to 11.5 MeV at multiple locations relevant to the PROSPECT experiment and future neutrino detectors. Gamma lines are identified and attributed to reactor and beamline sources (Table 7), reactor power scaling is confirmed to be linear (Section 3.2), and a Geant4-based detector response model is used with Richardson-Lucy unfolding to produce incident gamma flux spectra at six key positions (Section 6). The unfolded spectra are provided as supplemental CSV files under two illumination-geometry limits (isotropic and front-face). A consistency check is performed by feeding the unfolded spectrum into the PROSPECT simulation and comparing spectral shape against PROSPECT detector data (Section 7.4-7.5). A shielding study quantifies background reduction achievable with water-brick and lead configurations in the 30-60 keV range relevant to CEvNS detection (Section 5.4).

Significance. The paper provides a valuable, practical characterization of gamma backgrounds at a major reactor neutrino site, directly informing future CEvNS and IBD experiment design. Strengths include: (1) reproducible deliverables — the unfolded flux spectra are shipped as machine-readable supplemental CSV files for both response-model limits, along with measured spectra and metadata; (2) a falsifiable validation strategy — the PROSPECT simulation comparison provides a concrete, if shape-only, test of the unfolded source terms; (3) systematic coverage of spatial, temporal, and energy-dependent variations; (4) an independent cross-check of the Richardson-Lucy unfolding with a penalized-Poisson mirror-descent solver, demonstrating that the low-energy suppression artifact at the MIF location is response-model-driven rather than algorithmic (Section 6.4). The 59Ni 11.39 MeV line identification as a potential in-situ calibration feature for future experiments is a useful, concrete suggestion.

major comments (1)
  1. Section 7.4 states the PROSPECT simulation is 'normalized to minimize the chi-square difference with the data over the full plotted energy range.' The agreement claims in Section 7.5 (<10% from 200 keV to 1 MeV, ~25% from 1-6 MeV, factor of 2 from 6-11.5 MeV) therefore test spectral shape only, not absolute flux. The Conclusion (Section 8) acknowledges that 'the absolute flux normalization from the unfolded spectrum carries additional systematic uncertainty from the detector-response simulation' but this systematic is never quantified or bounded. The paper's central deliverable is described as 'quantitative source terms' (Section 1, Section 6), yet the only validation is shape-only. The authors should either (a) explicitly reframe the deliverable as 'quantitative spectral shape with normalization bracketed by the isotropic/front-face limits' and state clearly that absolute flux remains未经
minor comments (7)
  1. Table 5: the 109Cd efficiency measurements at 88 keV show 20-22% simulation disagreement, which is notably worse than all other energies (typically <4%). This is not discussed in the text. A brief comment on the likely cause (e.g., dead-layer model inadequacy at low energy) would help the reader assess the reliability of the unfolded flux below ~100 keV.
  2. Section 6.1: the dead-layer parameters are fitted only up to 1332 keV (Table 5). The text acknowledges the lack of high-energy efficiency calibration but the escape-peak ratio validation (Table 8) only tests relative peak areas, not absolute efficiency. Consider stating more explicitly that the absolute efficiency above 1332 keV is entirely model-dependent.
  3. Table 3: several relative peak areas have uncertainties larger than the central value (e.g., 214Pb at 295.2 keV: 0.455±0.793; 113Cd at 707.4 keV: 0.018±0.110). These entries should be flagged or the large uncertainties explained.
  4. Figure 22 caption: 'Rate [hz/MeV]' should be 'Rate [Hz/MeV]' for consistent capitalization of the unit.
  5. Section 5.3: the ~15% natural cadmium fraction in the tin layer is described as an order-of-magnitude estimate from a simplified model. The text could note whether this level is physically plausible given typical tin purity specifications, or whether it suggests an alternative origin for the 113Cd line.
  6. The paper would benefit from a concise summary table of all systematic uncertainties affecting the unfolded flux (counting statistics, dead-layer model, illumination geometry, energy resolution), even if some are only qualitatively bounded.
  7. Reference [14] URL contains a trailing double-quote character that should be removed.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for a careful and constructive report. The referee correctly identifies that the PROSPECT comparison in Section 7 is a shape-only validation and that the absolute flux normalization systematic is acknowledged but not quantified. We agree with the substance of this comment and will revise the manuscript accordingly.

read point-by-point responses

  1. Referee: Section 7.4 states the PROSPECT simulation is 'normalized to minimize the chi-square difference with the data over the full plotted energy range.' The agreement claims in Section 7.5 therefore test spectral shape only, not absolute flux. The Conclusion acknowledges that 'the absolute flux normalization from the unfolded spectrum carries additional systematic uncertainty from the detector-response simulation' but this systematic is never quantified or bounded. The paper's central deliverable is described as 'quantitative source terms' yet the only validation is shape-only. The authors should either (a) explicitly reframe the deliverable as 'quantitative spectral shape with normalization bracketed by the isotropic/front-face limits' and state clearly that absolute flux remains unvalidated, or (b) quantify the systematic.

    Authors: The referee is correct on all counts. The PROSPECT comparison in Section 7.4–7.5 is a shape-only test: the simulation is freely normalized to minimize chi-square, so the agreement figures (<10% from 200 keV to 1 MeV, ~25% from 1–6 MeV, factor of 2 from 6–11.5 MeV) validate spectral shape, not absolute flux. The Conclusion (Section 8) acknowledges this qualitatively but does not state it as plainly as it should, and the term 'quantitative source terms' in Sections 1 and 6 overstates what has been validated. We will revise the manuscript to adopt option (a): we will reframe the deliverable explicitly as 'quantitative spectral shape with absolute normalization bracketed by the isotropic and front-face response-model limits,' and we will state clearly that absolute flux remains unvalidated against an independent measurement. Specifically, we will make the following changes: (1) In Sections 1 and 6, replace 'quantitative flux models' / 'quantitative source terms' with language such as 'unfolded gamma flux spectra with spectral shape validated against PROSPECT data and absolute normalization bracketed by two response-model limits.' (2) In Section 7.4, add an explicit sentence stating that the normalization is a free parameter and that the comparison therefore tests spectral shape only. (3) In Section 7.5, preface the quantitative agreement statements with 'in spectral shape.' (4) In Section 8, strengthen the existing acknowledgment to state plainly: 'The absolute flux normalization is not independently validated; the isotropic and front-face response models provide a bracket on the plausible range, but residual detector-response mismodeling (as evidenced by the low-energy suppression artifact at the MIF location) means the true normalization could fall outside even this range revision: no

  2. Referee: The referee's comment appears to be cut off at 'absolute flux remains未经' — we interpret this as requesting that the authors state clearly that absolute flux remains unvalidated.

    Authors: We have addressed this interpretation above. If the referee intended a more specific request, we are happy to incorporate it in a subsequent revision. revision: no

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: the unfolded gamma spectra are derived from independent HPGe measurements with a Geant4 response model, and the PROSPECT validation is a shape-only consistency check, not a fit that defines the result.

full rationale

The paper's central deliverable—unfolded gamma flux spectra—is derived from HPGe detector measurements deconvolved via a Geant4-based migration matrix (Eq. 1, Section 6). The detector response model parameters (dead-layer thicknesses, charge radius) are fitted to independent efficiency calibration data from radioactive sources (Table 5, energies 59.5–1332.5 keV), not to the reactor gamma spectra being unfolded. The Richardson-Lucy unfolding is a standard deconvolution applied to measured data, not a fit to a target. The PROSPECT validation (Section 7.4–7.5) explicitly normalizes the simulation to minimize chi-square against PROSPECT data for shape comparison only; the paper does not claim this as an absolute flux prediction and acknowledges in the Conclusion that 'the absolute flux normalization from the unfolded spectrum carries additional systematic uncertainty from the detector-response simulation.' This is a limitation, not circularity: the unfolded spectra are not defined by the PROSPECT comparison. The self-citations (Refs [1, 13, 19]) are to prior PROSPECT results that provide independent detector data and building characterization, not to a theorem or ansatz that would force the present result. No step in the derivation chain reduces to its own inputs by construction. The shape-only nature of the PROSPECT validation and the unquantified absolute normalization uncertainty are correctness and completeness concerns, not circularity. The paper is self-contained against its stated benchmarks and does not exhibit self-definitional, fitted-input-as-prediction, or self-citation-load-bearing circularity patterns. Score 1 reflects the minor self-citation to prior PROSPECT work for context, which is not load-bearing for the unfolding result itself.

Assumptions & free parameters 8 free parameters · 4 assumptions · 0 invented entities

No new particles, forces, fields, or entities are postulated. The 113Cd contamination is an unexpected but not invented material presence; the cadmium is inferred from observed spectral lines, not postulated. The free parameters are all fitted detector response or shielding composition parameters, not new physics.

free parameters (8)
  • Top dead layer thickness = 1.3 mm
    Fitted to efficiency measurement data in Section 6.1; differs from manufacturer spec of 0.7 mm
  • Inner dead layer thickness = 3.6 mm
    Fitted to efficiency data; manufacturer spec was 0.3 micrometers
  • Side dead layer thickness = 0.65 mm
    Fitted to efficiency data in Section 6.1
  • Bottom dead layer thickness = 3.5 mm
    Fitted to efficiency data in Section 6.1
  • Charge radius parameter = 0.22 mm/MeV^(1/3)
    Fitted to efficiency data; controls charge collection model in Geant4
  • Energy resolution A coefficient = 0.98 keV
    Linear fit to peak sigma widths vs energy (Section 6.2)
  • Energy resolution B coefficient = 0.00018
    Linear fit to peak sigma widths vs energy (Section 6.2)
  • Cadmium fraction in tin layer = ~15% natural Cd (~2% 113Cd)
    Phenomenological fit to match 113Cd/207Pb peak ratio in Russian Doll spectrum; explicitly flagged as order-of-magnitude estimate only (Section 5.3)
assumptions (4)
  • domain assumption Geant4 accurately reproduces gamma transport physics (Compton scattering, photoelectric effect, pair production) in the HPGe detector and collimator geometry
    Section 6: the entire unfolding procedure depends on the simulated response matrix M being accurate. Validated partially via escape-peak ratios (Appendix B) but no high-energy efficiency calibration exists.
  • ad hoc to paper The two illumination geometry limits (isotropic and front-face) bracket the true angular distribution of gammas at each measurement location
    Section 6: these are the only two response models used. The paper acknowledges the true field is anisotropic but does not reconstruct the full angular distribution, claiming the two cases give a practical bracket.
  • domain assumption Reactor power linearly scales all gamma background components
    Section 3.2: confirmed empirically at 10% power showing ~10% rates, but assumed to hold across the full energy range and all source contributions.
  • domain assumption The spherical charge distribution model approximates charge collection physics adequately for flux estimation
    Section 6: charge within overlaps of sphere with dead layers is discarded. Detector non-linearity from charge trapping is not incorporated, deemed appropriate for flux estimation but not exact spectral shape.

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Cite this review

Pith. "Pith review of Gamma Backgrounds for Experiments at the High Flux Isotope Reactor." pith.science (2026). https://pith.science/paper/FTOQR4PG

@misc{pith2026260705834,
  author       = {Pith},
  title        = {Pith review of: Gamma Backgrounds for Experiments at the High Flux Isotope Reactor},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/FTOQR4PG}},
  note         = {Machine review of arXiv:2607.05834}
}
read the original abstract

This article describes the deployment of a germanium detector at Oak Ridge National Lab's High Flux Isotope Reactor (HFIR) for the purpose of understanding the energy and spatial distribution of the gamma field in the experiment hall where the Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) took data and future neutrino experiments could be located. The sources from both the reactor and the neutron beamlines are described in detail, along with their temporal variations due to reactor power and their spatial variations due to the geometry of the beamlines and building materials in the vicinity. Additionally, a shielding study was performed to assess the amount that backgrounds in tens of keV range can be mitigated. This work helps inform backgrounds for future experiments at reactors such as IBD-based neutrino measurements and CEvNS measurements.

Figures

Figures reproduced from arXiv: 2607.05834 by the authors.

Figure 1
Figure 1. Top down diagram of the core and beamlines HB3 and HB4 relative to the HFIR Experiment Hall. Compass rose indicates directional orientation. The placement of the Russian Doll shield (refer to Section 5 for more details) is located at the green circle at the lowest point of background radiation in front of the lead shield wall. The inner scintillator volume of where PROSPECT took data is outlined in blue. The concret… view at source ↗
Figure 2
Figure 2. shows an isometric drawing of the shield cart with the detector placed in the horizontal position and a picture of the cart deployed at the reactor [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Location of the MIF reactor-facing position along with its orientation (blue arrow) 4, Shield Center (brown star), and HB4 hotspot (orange star) 9. Starred locations were measured with the collimator facing down. The detector was left in this position for 20 hours while the reactor was at 100% operating power to obtain high statistics measurements. This measurement was repeated when the reactor was turned off [PITH… view at source ↗
Figures from the paper (23 more)
Figure 5
Figure 5. Figure 5: Ratios of rates in 500 keV increments to the spectrum at 100% power for various periods during the ramp up for cycle 491. Note that only power ranges are known based on the operator announcing the beginning of a ramp up to a set power level with the exception of the 10…
Figure 4
Figure 4. Figure 4: Measured energy spectrum with collimator facing the reactor positioned west of the lead shield wall, just under the MIF box (see figure 3, blue arrow). Reactor-on in blue, reactor￾off in red. See [PITH_FULL_IMAGE:figures/full_fig_p005_4.png]
Figure 6
Figure 6. Figure 6: Rates between 30 keV and 11465 keV over time in the collimated Ge detector while in the MIF reactor-facing position (see [PITH_FULL_IMAGE:figures/full_fig_p006_6.png]
Figure 7
Figure 7. Figure 7: Rates between 50 keV and 11400 keV measured with the Ge detector inside the lead collimator facing down towards the floor. Blue box indicates the region of the PROSPECT active scintillator volume, the green circle represents the location of the Russian doll shield, the…
Figure 8
Figure 8. Figure 8: Measured gamma rates between 50 and 11400 keV. Scan is along the east face of the PROSPECT detector active volume. Low x values correspond to the north side of the detector. High rates correspond to the detector being pointed at the HB4 hot spot. 5. Russian Doll Shield…
Figure 10
Figure 10. Figure 10: Cutout drawing of Russian Doll shielding. From outer to inner shielding layers are steel (green), lead (light grey), tin (see detail B), copper (see detail B), borated polyethylene (dark grey) and lithiated polyethylene (teal). The brown cylinder below the detector is…
Figure 11
Figure 11. Figure 11: Russian Doll shielding water bricks. Background shows the lead shield wall. capture on the germanium. At these levels of attenuation with the baseline RD configuration, gamma backgrounds are about one order of magnitude away from achieving a detec￾tor environment with…
Figure 12
Figure 12. Figure 12: Scaled front-elevation schematics of the four shielding configurations used with the Russian Doll shield. Water bricks formed an open-top square wall around the full RD assembly, including the stand, with a small gap between the wall and the stand legs. The lead-under…
Figure 13
Figure 13. Figure 13: Energy spectrum with Russian doll shielding, red reactor on blue reactor off. Reactor on features are due to neutron captures on shielding materials, especially 113Cd. runs were not conducted in low-gain mode (11.4 MeV range) for all shielding configurations, rates ar…
Figure 14
Figure 14. Figure 14: Energy spectra taken in the Russian Doll shield in high gain mode (30–60 keV). Comparison shown is between different shield configurations described in Section 5.4. Error bars are from counting statistics. sampling a Gaussian with width proportional to 𝐴 + 𝐵 × 𝐸, wher…
Figure 15
Figure 15. Figure 15: Linear fit to sigma widths as a function of energy. Fits were performed on the major gamma lines from 59Ni, 58Ni, 27Al, 9Be, 41Ar, 40K, and 60Co [PITH_FULL_IMAGE:figures/full_fig_p014_15.png]
Figure 17
Figure 17. Figure 17: Comparison of raw measured spectra (blue, left axis) and unfolded gamma flux spectra (red, right axis) for each measurement location. The measured spectra represent the detector response while the unfolded spectra represent the estimated incident gamma flux. resulting…
Figure 18
Figure 18. Figure 18: Unfolded incident gamma flux spectra for all six measurement locations using the isotropic-response case. Vertical units are Hz/mm2/keV. Measurement numbers correspond to the positions in [PITH_FULL_IMAGE:figures/full_fig_p016_18.png]
Figure 19
Figure 19. Figure 19: Comparison of the two unfolding response-model limits for each measurement location. Blue curves show the isotropic response, red curves show the front-face directional response, and the shaded band indicates the bracket between them. This band is used as the plausibl…
Figure 20
Figure 20. Figure 20: Prompt-like detected singles rates (Hz) during reactor-on vs segment number. Segments 15, 16, and 30 used for gamma simulation comparison are labeled. Missing segments had non-functioning PMTs on one or both ends during the measurement campaign. Source: [1] 7.3. PROSP…
Figure 21
Figure 21. Figure 21: Comparison of overnight spectra acquired with the collimated Ge detector at three locations along the PROSPECT de￾tector boundary. Inset depicts each measurement’s position relative to the PROSPECT scintillator volume boundary (light blue), with the solid line above t…
Figure 22
Figure 22. Figure 22 [PITH_FULL_IMAGE:figures/full_fig_p020_22.png]
Figure 23
Figure 23. Figure 23: Peaks labelled for spectrum taken under the MIF with collimator pointed at the reactor core, 700 - 1900 keV [PITH_FULL_IMAGE:figures/full_fig_p024_23.png]
Figure 24
Figure 24. Figure 24: Peaks labelled for spectrum taken under the MIF with collimator pointed at the reactor core, 6700 - 7900 keV. Heffron, B: Preprint submitted to Elsevier Page 24 of 31 [PITH_FULL_IMAGE:figures/full_fig_p024_24.png]
Figure 25
Figure 25. Figure 25: Peaks labelled for spectrum taken under the MIF with collimator pointed at the reactor core, 7900 - 9100 keV [PITH_FULL_IMAGE:figures/full_fig_p025_25.png]
Figure 26
Figure 26. Figure 26: Peaks labelled for spectrum taken under the MIF with collimator pointed at the reactor core, 9100 - 10300 keV. Heffron, B: Preprint submitted to Elsevier Page 25 of 31 [PITH_FULL_IMAGE:figures/full_fig_p025_26.png]
Figure 27
Figure 27. Figure 27: Peaks labelled for spectrum taken under the MIF with collimator pointed at the reactor core, 10300 - 11500 keV. Heffron, B: Preprint submitted to Elsevier Page 26 of 31 [PITH_FULL_IMAGE:figures/full_fig_p026_27.png]
Figure 28
Figure 28. Figure 28: Detected photopeak rates from corrected simulations for the two response-model limits used in the unfolding: an isotropic 1 Hz/mm2 gamma flux over the outer surface of the collimator-detector system, and a uniform 1 Hz/mm2 gamma flux directed into the detector-collima…

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Pith tools

Reviewed July 8, 2026 · model on record in the stance chip above.