Scintillation Light Detection in Polycrystalline Diamond Using Single Photon Detectors

Aleksey Bolotnikov; Erik M. Muller; Niccol\`o Gallice; Thomas Tsang

REVIEW 4 major objections 5 minor 14 references

Scintillation Light Detection in Polycrystalline Diamond Using Single Photon Detectors

T0 review · 4 major / 5 minor · reviewed 2026-08-07 · deepseek-v4-flash

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Pith's one-line read Polycrystalline diamond powder plus 6LiF can make a compact, gamma-insensitive thermal neutron detector with per-area efficiency comparable to a large 3He tube.

desk verdict Powder diamond scintillation is a real proof-of-concept, but the neutron efficiency claims outrun the measurements. read the letter →

arxiv 2502.09800 v1 pith:4VXDUH6S submitted 2025-02-13 physics.ins-det

Niccolò Gallice , Aleksey Bolotnikov , Erik M. Muller , Thomas Tsang This is my paper · ORCID

classification physics.ins-det

keywords polycrystallinediamondscintillationdetectionthermalneutronsiliconphotomultiplier6LiFconverterportabledetectorgammainsensitivitypowder

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 argues that inexpensive polycrystalline diamond powder can serve as a scintillator for particle detection, not just costly single-crystal diamond. It reports that diamond powders emit blue-green light under $\alpha$ irradiation, and that a prototype mixing diamond powder with $^{6}\mathrm{LiF}$ registers thermal neutrons through the $^{6}\mathrm{Li}(n,\alpha)t$ reaction. A measured count-rate comparison implies the $1.4\,\mathrm{cm}^{2}$ prototype has roughly $1.2$ times the per-area efficiency of a $576\,\mathrm{cm}^{2}$ $^{3}\mathrm{He}$ detector, while a Monte Carlo simulation predicts about $50\%$ thermal neutron detection efficiency for an optimized geometry. Because carbon is low-Z, the detector stays insensitive to gamma rays, which removes a common background problem for neutron counters. The practical upshot is a small, cheap, portable neutron detector that could reduce dependence on scarce $^{3}\mathrm{He}$.

What carries the argument

The operative mechanism is the $^{6}\mathrm{Li}(n,\alpha)t$ conversion reaction: a thermal neutron absorbed by $^{6}\mathrm{Li}$ releases a $2.73\,\mathrm{MeV}$ $\alpha$ particle and a $2.05\,\mathrm{MeV}$ triton, and these charged particles deposit energy in surrounding diamond powder grains, which then scintillate. The prototype's active geometry is a powder of $30$–$40\,\mu\mathrm{m}$ diamond grains mixed with $^{6}\mathrm{LiF}$, coated in layers and covered by an aluminum reflector, read out by a 4-by-4 array of silicon photomultipliers. In the simulation the grains are modeled as $20\,\mu\mathrm{m}$ cubes spaced $73$–$430\,\mu\mathrm{m}$ apart inside a $^{6}\mathrm{LiF}$ block, with a light yield of $3000$ photons per MeV, an effective attenuation length of $1\,\mathrm{mm}$, and a detection threshold of $20$ collected photons. The emission band from $400$ to $600\,\mathrm{nm}$ is what makes the silicon-photomultiplier coupling efficient, and the low-Z carbon matrix is what suppresses gamma response.

What would settle it

Calibrate the absolute scintillation light yield of the diamond powder (photons per MeV) under alpha and triton irradiation with a photon-counting setup; if the measured value is well below 3000 photons per MeV, the simulated ~50% efficiency is unattainable and the detector's real performance would need re-evaluation.

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Extended reading notes

Core claim

The authors claim that polycrystalline diamond powder coupled to a $^{6}\mathrm{LiF}$ neutron-conversion layer and read out by silicon photomultipliers is a working scintillation neutron detector. In their measurement a $1.4\,\mathrm{cm}^{2}$ prototype recorded $0.44\,\mathrm{Hz}$ from a moderated $^{252}\mathrm{Cf}$ source while a $576\,\mathrm{cm}^{2}$ $^{3}\mathrm{He}$ detector recorded $147\,\mathrm{Hz}$; assuming a uniform neutron flux, the implied efficiency ratio is $\epsilon_{\mathrm{diamond}}/\epsilon_{\mathrm{^{3}He}}\sim 1.2$. A Monte Carlo radiation-transport simulation of diamond grains embedded in $^{6}\mathrm{LiF}$ predicts roughly $50\%$ thermal neutron detection efficiency, with the caveat that this rests on an assumed light yield of $3000$ photons per MeV and a $1\,\mathrm{mm}$ attenuation length. Photoluminescence spectra put the emission in the $400$–$600\,\mathrm{nm}$ band, matching silicon-photomultiplier sensitivity, and the low atomic number of carbon gives inherent gamma insensitivity.

Load-bearing premise

The simulated 50% thermal neutron efficiency depends on an assumed light yield of 3000 photons per MeV for diamond powder, which the paper does not measure; if the real powder yields fewer photons, the design cannot reach the predicted efficiency.

Editorial extensions

If this is right

A thermal neutron detector with only $1.4\,\mathrm{cm}^2$ of active area can match the per-area counting efficiency of a $576\,\mathrm{cm}^2$ $^{3}\mathrm{He}$ tube, so detector size and cost can shrink dramatically.
Because the detector is gamma-insensitive by material choice, portable neutron counting no longer needs bulky shielding or pulse-shape discrimination against gamma backgrounds.
The simulation shows that thickness and grain packing can be tuned to reach roughly $50\%$ thermal neutron efficiency, giving a design target for a fieldable instrument.
If the prototype performance holds, $^{6}\mathrm{LiF}$-loaded diamond powder offers a route away from scarce and expensive $^{3}\mathrm{He}$ for thermal neutron detection.
Silicon photomultiplier readout keeps the detector low-voltage and compact, compatible with handheld or remote operation.

Reading between the lines

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

The assumed $3000$ photons per MeV light yield is not measured in the paper; a calibrated measurement would either confirm or shift the simulated $50\%$ efficiency and the optimal detector thickness.
The same powder-plus-converter architecture could be adapted to $^{10}\mathrm{B}$ or gadolinium converters to cover different neutron energy ranges, since only the conversion material changes.
Because each prototype cell is small and read out independently on a silicon-photomultiplier matrix, the geometry could be extended to a position-sensitive neutron imager without changing the physics.
The efficiency ratio of about $1.2$ relies on a uniform-flux assumption that the paper does not verify; swapping source positions or scanning the source across both detectors would test how the ratio behaves in realistic gradients.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Quick take: the paper shows that diamond powder scintillates under alpha irradiation and that a 6LiF-loaded powder prototype produces neutron-correlated pulses. That is a legitimate, modest experimental result. The photoluminescence and alpha spectra are the strongest part. What does not hold up is the abstract's gamma-insensitivity claim and the efficiency comparison to a 3He detector.

The alpha measurements in Sec. 3 are honest: no peak, just a bump around 300 PE, and they say resolution is poor. That is fine for a proof of concept. The Geant4 model in Sec. 4 is the weak spot. The 3000 photons/MeV light yield and 1 mm attenuation length are assumed, not measured or cited. The simulated 50% efficiency depends directly on these numbers and on the 20-photon threshold. If the true powder yield is lower, the efficiency drops. The authors do not calibrate the simulation against the alpha spectra.

The experimental efficiency ratio is also shaky. They assume a uniform neutron flux over both detectors, but the geometry has the source on top of the diamond prototype, which sits on the 3He detector. The 3He sees a different flux, shadowed by the prototype. Converting 0.44 Hz over 1.4 cm^2 to 147 Hz over 576 cm^2 gives a ratio of about 1.2, but there is no uncertainty, no background subtraction, and no accounting for the source-detector geometry. So this is not a validation of the simulation.

The gamma insensitivity claim is asserted in the intro and abstract but never measured. A single measurement with a gamma source would have helped.

That said, the paper is not a waste of time. The observation that cheap diamond powder scintillates enough to be read out by SiPMs is worth putting on record. The neutron prototype shows a signal. The flaws are addressable: measure the light yield, add error bars, test with gamma, and redo the efficiency comparison with a better geometry model.

Who is this for? People building portable neutron monitors or working on diamond scintillators. It is a conference-style result, not a definitive study.

For peer review: I'd send it out. A good referee can push the authors to fix the efficiency analysis and tone down the abstract. The experimental core is real.

Referee Report

4 major / 5 minor

Summary. The paper reports exploratory measurements and simulations for using polycrystalline diamond powder as a scintillator for alpha particles and for a thermal neutron detector when mixed with 6LiF. Photoluminescence spectra are shown for several diamond samples, alpha-induced scintillation is observed with a SiPM readout, a Geant4 simulation of the neutron-detector geometry is described, and a prototype is compared with a large 3He detector using a 252Cf source. The abstract claims that the detector can achieve significant detection efficiency while remaining insensitive to gamma radiation.

Significance. If the main claims were fully supported, the work would be useful and timely: a cheap, compact, powder-based diamond scintillator that detects thermal neutrons with an efficiency comparable to a large 3He tube would be attractive for portable neutron counting. The paper has several genuine strengths: photoluminescence spectra are measured over a range of samples; the alpha-excited scintillation response of diamond powders is demonstrated with an imaging SiPM array; and a Geant4 simulation is used to explore the trade-off between detector thickness and optical-photon collection. However, the current evidence is not sufficient to establish the quantitative claims in the abstract, because the simulation relies on unmeasured optical parameters, the experimental efficiency comparison rests on an unjustified uniform-flux assumption and has no quoted uncertainty, and the gamma-insensitivity claim is not backed by any gamma-ray measurement. The paper is best read as a feasibility study, not as a validated detector characterization.

major comments (4)

[Section 4, Geant4 simulation paragraph] The simulation assigns the diamond powder a light yield of 3000 photons/MeV and an effective attenuation length of 1 mm, with no measurement or citation. Since the simulated detection efficiency is defined as the fraction of events with at least 20 detected photons, the quoted approximately 50% thermal-neutron efficiency scales directly with these parameters. A sensitivity scan over light yield and attenuation length, or an experimental calibration of those values from the alpha-particle spectra, is needed before the simulated efficiency can be regarded as a prediction rather than an assumption.
[Section 4, last paragraph (rate comparison)] The conversion of the measured count rates (0.44 Hz for the diamond prototype and 147 Hz for the 3He detector) into the efficiency ratio epsilon_diamond/epsilon_He3 approximately 1.2 relies on the sentence 'Assuming a uniform neutron flux'. The experimental geometry, with the 1.4 cm2 prototype stacked directly between the 252Cf source (plus paraffin) and the 576 cm2 3He detector, cannot produce a uniform flux over both detectors: the prototype shadows the central region of the 3He tube, and the 3He tube sees a strongly varying flux over its area. The ratio is therefore not a reliable validation of the simulation. In addition, the two rates are quoted without statistical or systematic uncertainties, so even the qualitative 'comparable efficiency' conclusion is not quantitatively supported. A calibrated neutron field or a flux-profile simulation, together with uncertainty propagation, is required.
[Abstract and Section 4, first paragraph] The abstract claims the detector 'remain[s] insensitive to gamma radiation', but no gamma-ray irradiation measurement appears anywhere in the manuscript. Section 4 supports the claim only by the low-atomic-number argument ('Diamonds are primarily insensitive to gamma radiation due to their low atomic number'). In an instrumentation paper, a claim of gamma insensitivity should be backed by data, e.g., a measurement with a gamma source such as 137Cs or 60Co showing negligible response, or by an explicit statement that the claim is a forward-looking projection. As written, the abstract overstates the experimental content of the paper.
[Section 3, alpha-scintillation spectra] The alpha-excitation spectra in Figure 2b are presented as histograms without error bars, a fitted peak energy, or a stated background/dark-count subtraction. The text notes that the diamond samples 'do not exhibit a noticeable peak' and that the powders show 'a bump structure around 300 PE'. This demonstrates qualitatively that scintillation light is produced, but it does not allow the measured signal to be converted into an absolute light yield in photons/MeV. Such a conversion would be needed to anchor the 3000 photons/MeV value used in the Geant4 simulation, so the current alpha data cannot serve as a calibration input for the simulation.

minor comments (5)

[Section 3, first paragraph] The phrase 'one CVD high-purity monocristal diamond with1 indiameter' should read 'one CVD high-purity monocrystalline diamond with 1 in diameter'.
[Acknowledgments] The Acknowledgments section begins 'Weaknowledge DOE...'; this appears to be a typo for 'We acknowledge'.
[Figure 2b] The caption states that the gray line is the LSO reference, but the figure does not label the other traces; a legend or a list matching each curve to samples L1-L4 and the CVD diamond would improve interpretability.
[Figure 4b] The text says the histograms are 'arranged according to their physical location', but the figure provides no coordinate grid or channel labels; the reader cannot tell which channel or detector pixel each panel represents.
[Section 2, first paragraph] The paper states that the YAG laser has a wavelength of 266 nm and a pulse duration of 20 ps, but the pulse energy and repetition rate are not given; these quantities affect the photoluminescence intensity comparison and could be added.

Circularity Check

0 steps flagged · score 0.0 of 10

No circular derivation found: the simulated efficiency rests on a stated light-yield input, and the measured rate-ratio comparison is an explicit proportional calculation under a stated uniform-flux assumption.

full rationale

The paper's central simulation (Sec. 4) is a forward Geant4 model with explicitly stated optical inputs (refractive index 2.46, attenuation length 1 mm, light yield 3000 photon/MeV) and a threshold definition (at least 20 detected photons); these inputs are not fitted to the efficiency target and the efficiency is not an algebraic rearrangement of any measured quantity. The only quantitative comparison to data is the count-rate ratio 0.44 Hz/147 Hz converted to an efficiency ratio via the stated surface areas 1.4 cm^2/576 cm^2 under the explicit assumption of uniform neutron flux; this is a direct proportionality, not a fitted parameter renamed as a prediction. The 3He reference detector is cited for its hardware design, but the load-bearing number is the measured 147 Hz rate, not a self-cited efficiency value. The unmeasured light-yield and uniform-flux assumptions are correctness risks, not circularities; they do not reduce a derived result to its own input by construction.

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

The central performance claims rest on several assumed optical and geometrical inputs in the Geant4 simulation, an untested uniform-flux assumption in the rate comparison, and an untested gamma-insensitivity assumption. No new physical entities are postulated, so invented_entities is empty.

free parameters (4)

Diamond light yield in Geant4 = 3000 photons/MeV
Assumed without measurement or citation; directly drives simulated photon counts and efficiency.
Diamond attenuation length in Geant4 = 1 mm
Assumed; strongly affects light collection from the powder bed.
6LiF attenuation length in Geant4 = 500 µm
Assumed optical parameter in the simulation.
Detection threshold in simulation = 20 photons
Choice defines what counts as a detected neutron; changing it changes the efficiency.

assumptions (4)

domain assumption Deposited energy in diamond powder produces 3000 photons/MeV of scintillation light, linearly with energy
Simulation input in Sec 4; not derived from the alpha measurements.
domain assumption The neutron flux is uniform across the 1.4 cm2 diamond prototype and the 576 cm2 3He detector
Used in Sec 4 to convert rates into efficiency ratio; likely violated by source geometry.
domain assumption Low atomic number guarantees insensitivity to gamma radiation
Stated in Sec 4, no gamma irradiation test reported.
domain assumption The SiPM trigger threshold just above dark count does not bias event selection
Sec 3; no dark-count or background spectra shown.

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Cite this review

Pith. "Pith review of Scintillation Light Detection in Polycrystalline Diamond Using Single Photon Detectors." pith.science (2026). https://pith.science/paper/4VXDUH6S

@misc{pith2026250209800,
  author       = {Pith},
  title        = {Pith review of: Scintillation Light Detection in Polycrystalline Diamond Using Single Photon Detectors},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/4VXDUH6S}},
  note         = {Machine review of arXiv:2502.09800}
}

abstract

This study investigates the scintillation properties of polycrystalline diamond for particle detection applications, particularly in neutron and alpha radiation environments. Polycrystalline diamonds provide a cost-effective alternative to monocrystalline diamonds while retaining essential detection properties. Photoluminescence measurements were performed to analyze emission spectra, revealing distinct characteristics based on impurity content and crystallinity. Scintillation responses were assessed using Silicon Photomultipliers (SiPMs), demonstrating the capability of polycrystalline diamond powders to respond to alpha irradiation, albeit with reduced resolution compared to traditional scintillators. A prototype neutron detector was developed by combining diamond powder with neutron-sensitive ${}^6$LiF, and its performance was evaluated through experimental testing and Geant4 simulations. The findings indicate that polycrystalline diamond-based detectors can achieve significant detection efficiency while remaining insensitive to gamma radiation, offering potential for portable neutron detection applications.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

14 extracted references · 13 canonical work pages

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Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.

[1] [1]

Bohon, E

J. Bohon, E. Muller and J. Smedley,Development of diamond-based X-ray detection for high-flux beamline diagnostics,Journal of Synchrotron Radiation17(2010) 711

work page 2010

[2] [2]

M. Zou, J. Bohon, J. Smedley, J. Distel, K. Schmitt, R.-Y. Zhu et al.,Proton radiation effects on carrier transport in diamond radiation detectors, AIP Advances10(2020) 025004

work page 2020

[3] [3]

Bergonzo, D

P. Bergonzo, D. Tromson and C. Mer,Radiation detection devices made from CVD diamond, Semiconductor Science and Technology18(2003) S105

work page 2003

[4] [4]

H. Kagan,Diamond radiation detectors may be forever!,Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment546(2005) 222

work page 2005

[5] [5]

Dean, P.J

P.J. Dean, P.J. Kennedy and J.E. Ralph,Particle Excited Luminescence in Diamond, Proceedings of the Physical Society76(1960) 670

work page 1960

[6] [6]

Nam, P.J

T.L. Nam, P.J. Fallon, R.J. Keddy, H.J. van Rĳn and J. Andrews,Detection of nuclear radiation by scintillation counting using synthetic diamond,International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes40 (1989) 657

work page 1989

[7] [7]

Jeske, D

J. Jeske, D. Lau, X. Vidal, L. McGuinness, P. Reineck, B. Johnson et al.,Stimulated emission from nitrogen-vacancy centres in diamond,Nature Communications8 (2017)

work page 2017

[8] [8]

Lu, Y.-C

H.-C. Lu, Y.-C. Peng, S.-L. Chou, J.-I. Lo, B.-M. Cheng and H.-C. Chang,Far-uv-excited luminescence of nitrogen-vacancy centers: Evidence for diamonds in space,Angewandte Chemie129 (2017) 14661 [https://onlinelibrary.wiley.com/doi/pdf/10.1002/ange.201707389]

doi:10.1002/ange.201707389 2017