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arxiv: 2606.26190 · v1 · pith:DKDNGA5Jnew · submitted 2026-06-24 · ⚛️ physics.ins-det

Application of surface coating for radon mitigation in rare-event searches

Florian J\"org , Guillaume Eurin , Hardy Simgen This is my paper

Pith reviewed 2026-06-26 01:12 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords radon mitigationsurface coatingelectroplatingrare-event searchesbackground reductionradon emanationstainless steellow-background detectors
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0 comments X

The pith

Copper electroplating reduces radon emanation from steel by a factor of 1000

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

Rare-event searches for dark matter and neutrino properties face dominant backgrounds from radon gas emanating from detector materials. The authors developed an electroplating technique to apply copper coatings that suppress the 222Rn emanation rate from a 226Ra-implanted stainless steel sample by three orders of magnitude. This surface treatment targets radioactive contamination at the origin rather than requiring bulk material purification. If the reduction holds under real detector conditions, the approach could relax constraints on material selection and simplify background control in these experiments. Readers would care because lower radon levels directly increase the reach of searches for fundamental physics signals.

Core claim

The paper reports development of a copper electroplating method applied to a stainless steel sample implanted with 226Ra. Measurements show this coating produces a thousandfold reduction in the 222Rn emanation rate. The work positions surface coatings as a practical mitigation strategy for radon backgrounds that commonly limit sensitivity in rare-event searches for dark matter and the Majorana nature of neutrinos.

What carries the argument

The copper electroplating layer deposited on the surface of the 226Ra-implanted stainless steel sample, functioning as a barrier to radon gas release.

If this is right

  • Radon backgrounds from surface contamination in detectors can be reduced by three orders of magnitude with copper coatings.
  • Stainless steel parts become viable for low-background applications after electroplating treatment.
  • Surface coatings provide an alternative to ultra-pure bulk material selection for background control.
  • The method addresses emanation as a dominant background mechanism without altering internal material composition.

Where Pith is reading between the lines

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

  • If the coating proves compatible with liquid noble gases, it could be applied directly inside xenon or argon detectors.
  • The technique might extend to other surface contaminants or detector geometries beyond flat steel samples.
  • Uniformity and long-term adhesion on large or complex components would need separate validation before widespread use.

Load-bearing premise

The copper coating remains stable, adherent, and free of new radioactive contaminants over multi-year timescales under cryogenic or vacuum conditions typical of rare-event detectors.

What would settle it

Measure the 222Rn emanation rate from the coated sample after several years of exposure to vacuum or cryogenic temperatures; a return toward the uncoated rate would falsify lasting mitigation.

read the original abstract

Rare-event searches offer a powerful avenue for investigating some of the most fundamental questions in modern physics, most prominently the particle nature of dark matter and the possible Majorana nature of the neutrino. Often, their dominant source of background comes from the radioactive noble gas radon emanating from materials. We report on a novel strategy to mitigate this background by the application of coating layers. A method for electroplating of copper was developed that showed a thousandfold reduction of the $^{222}$Rn emanation rate from a $^{226}$Ra-implanted stainless steel sample.

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

2 major / 1 minor

Summary. The manuscript reports a novel strategy for radon mitigation in rare-event searches via surface coatings. It describes the development of a copper electroplating method applied to a 226Ra-implanted stainless steel sample, claiming a thousandfold reduction in the 222Rn emanation rate.

Significance. If the measurement is reproducible and the coating remains stable, this approach could meaningfully reduce a dominant background in dark matter and neutrinoless double-beta decay experiments. The method is practical and material-agnostic in principle, offering a potential advantage over bulk material purification if long-term performance is demonstrated.

major comments (2)
  1. [Abstract] Abstract: the central claim of a thousandfold reduction in 222Rn emanation rate is presented without any description of sample preparation, electroplating parameters, emanation measurement technique, error bars, control samples, or replicate measurements, rendering the result impossible to evaluate.
  2. [Abstract] Abstract: the manuscript provides only a single post-coating measurement and supplies no data on coating adhesion, outgassing of plating residues, diffusion through the layer, or performance after thermal cycling or prolonged exposure to vacuum/cryogenic conditions, which are load-bearing for applicability to multi-year rare-event detectors.
minor comments (1)
  1. The abstract would be strengthened by a concise statement of the measurement method and any quantitative uncertainty on the reported reduction factor.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments on our manuscript. We address each major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the central claim of a thousandfold reduction in 222Rn emanation rate is presented without any description of sample preparation, electroplating parameters, emanation measurement technique, error bars, control samples, or replicate measurements, rendering the result impossible to evaluate.

    Authors: The abstract is a concise summary; the full manuscript describes the 226Ra implantation into stainless steel, the copper electroplating process parameters, and the radon emanation measurement setup. Error bars are based on Poisson counting statistics from the detector. The result is from a single implanted sample with pre- and post-coating measurements; no additional replicates or separate control samples were included. We will revise the abstract to reference the methods and note the single-sample demonstration. revision: yes

  2. Referee: [Abstract] Abstract: the manuscript provides only a single post-coating measurement and supplies no data on coating adhesion, outgassing of plating residues, diffusion through the layer, or performance after thermal cycling or prolonged exposure to vacuum/cryogenic conditions, which are load-bearing for applicability to multi-year rare-event detectors.

    Authors: We agree the manuscript reports only the initial post-coating emanation reduction and contains no data on adhesion, outgassing, diffusion, or long-term performance under thermal cycling or cryogenic/vacuum conditions. This is a proof-of-principle study focused on the initial mitigation effect. We will add a discussion section explicitly addressing these limitations and the requirements for multi-year detector use. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental result without derivation chain

full rationale

The paper reports development and testing of an electroplating method for copper coatings, with the central result being a measured thousandfold reduction in 222Rn emanation from a specific sample. No equations, first-principles derivations, fitted parameters presented as predictions, or self-citation chains appear in the provided text. The work is a direct experimental measurement whose validity rests on the reported data rather than any reduction to its own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No free parameters, axioms, or invented entities are invoked; the work is a direct experimental measurement of emanation rate before and after coating.

pith-pipeline@v0.9.1-grok · 5612 in / 984 out tokens · 20030 ms · 2026-06-26T01:12:59.961403+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

41 extracted references · 6 linked inside Pith

  1. [1]

    United Nations, 2018 ed., 2021

    United Nations Department for General Assembly and Conference Management,Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2018. United Nations, 2018 ed., 2021

    2018

  2. [2]

    http://www.nndc.bnl.gov/ensarchivals/,

    ENSDF database, “http://www.nndc.bnl.gov/ensarchivals/,” Nov, 2023

    2023

  3. [3]

    Neutrinoless Double Beta Decay,

    H. Päs and W. Rodejohann, “Neutrinoless Double Beta Decay,”New J. Phys.17no. 11, (2015) 115010, arXiv:1507.00170 [hep-ph]

    Pith/arXiv arXiv 2015

  4. [4]

    Dark matter direct-detection experiments,

    T. Marrodán Undagoitia and L. Rauch, “Dark matter direct-detection experiments,”J. Phys. G43no. 1, (2016) 013001,arXiv:1509.08767 [physics.ins-det]. 5.BOREXINOCollaboration, C. Arpesellaet al., “Measurements of extremely low radioactivity levels in BOREXINO,”Astropart. Phys.18(2002) 1–25, arXiv:hep-ex/0109031

    Pith/arXiv arXiv 2016

  5. [5]

    Measurements of extremely low radioactivity levels in stainless steel for gerda,

    W. Maneschg, M. Laubenstein, D. Budjáš, W. Hampel, G. Heusser, K. Knöpfle, B. Schwingenheuer, and H. Simgen, “Measurements of extremely low radioactivity levels in stainless steel for gerda,”Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment593no. 3, (2008) 448–453. https://www.sc...

    2008

  6. [6]

    Systematic study of trace radioactive impurities in candidate construction materials for exo-200,

    D. Leonardet al., “Systematic study of trace radioactive impurities in candidate construction materials for exo-200,”Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment591no. 3, (2008) 490–509.https://www.sciencedirect.com/ science/article/pii/S016890020800346X. 8.LZCollaboration, ...

    arXiv 2008

  7. [7]

    Evaluation of radon adsorption efficiency values in xenon with activated carbon fibers,

    Y . Nakano, K. Ichimura, H. Ito, T. Okada, H. Sekiya, Y . Takeuchi, S. Tasaka, and M. Yamashita, “Evaluation of radon adsorption efficiency values in xenon with activated carbon fibers,”PTEP2020no. 11, (2020) 113H01,arXiv:2003.11705 [physics.ins-det]

    arXiv 2020

  8. [8]

    Radon depletion in xenon boil-off gas,

    S. Bruenner, D. Cichon, S. Lindemann, T. Marrodán Undagoitia, and H. Simgen, “Radon depletion in xenon boil-off gas,”Eur. Phys. J.C77no. 3, (2017) 143,arXiv:1611.03737

    Pith/arXiv arXiv 2017

  9. [9]

    Online 222 Rn removal by cryogenic distillation in the XENON100 experiment,

    XENON100Collaboration, E. Aprileet al., “Online 222 Rn removal by cryogenic distillation in the XENON100 experiment,”Eur. Phys. J. C77no. 6, (2017) 358, arXiv:1702.06942 [physics.ins-det]

    Pith/arXiv arXiv 2017

  10. [10]

    Design, construction and commissioning of a high-flow radon removal system for XENONnT,

    M. Murra, D. Schulte, C. Huhmann, and C. Weinheimer, “Design, construction and commissioning of a high-flow radon removal system for XENONnT,” arXiv:2205.11492 [physics.ins-det]. 15.XENON CollaborationCollaboration, E. Aprileet al., “Offline tagging of radon-induced backgrounds in xenon1t and applicability to other liquid xenon time projection chambers,”P...

    arXiv 2024

  11. [11]

    High sensitivity radon emanation measurements,

    G. Zuzel and H. Simgen, “High sensitivity radon emanation measurements,”Appl. Radiat. Isot.67no. 5, (2009) 889 – 893. 9 21.XENONCollaboration, E. Aprileet al., “ 222Rn emanation measurements for the XENON1T experiment,”Eur. Phys. J. C81no. 4, (2021) 337, arXiv:2009.13981 [physics.ins-det]

    arXiv 2009

  12. [12]

    S. A. Brünner,Mitigation of 222Rn induced background in the XENON1T dark matter experiment. PhD thesis, University of Heidelberg, 2017

    2017

  13. [13]

    Hamamatsu,Large photosensitive area Si PIN photodiodes (S3204/S3584 series), 2021

    2021

  14. [14]

    Neutralisation rate and the fraction of the positive 218Po-clusters in air,

    P. Pagelkopf and J. Porstendörfer, “Neutralisation rate and the fraction of the positive 218Po-clusters in air,” Atmos. Environ.37no. 8, (Mar, 2003) 1057–1064

    2003

  15. [15]

    Jörg,From 222Rn measurements in XENONnT and HeXe to radon mitigation in future liquid xenon experiments

    F. Jörg,From 222Rn measurements in XENONnT and HeXe to radon mitigation in future liquid xenon experiments. PhD thesis, Heidelberg U., 2022

    2022

  16. [16]

    Highly sensitive gamma-spectrometers of GERDA for material screening: part 2,

    D. Budjáš, W. Hampel, M. Heisel, G. Heusser, M. Keillor, M. Laubenstein, W. Maneschg, G. Rugel, S. Schönert, H. Simgen,et al., “Highly sensitive gamma-spectrometers of GERDA for material screening: part 2,”arXiv:0812.0768

    Pith/arXiv arXiv

  17. [17]

    Underground measurements of radioactivity,

    M. Laubenstein, M. Hult, J. Gasparro, D. Arnold, S. Neumaier, G. Heusser, M. Köhler, P. Povinec, J.-L. Reyss, M. Schwaiger,et al., “Underground measurements of radioactivity,”Appl. Radiat. Isot.61 no. 2-3, (2004) 167–172

    2004

  18. [18]

    A 220Rn source for the calibration of low-background experiments,

    R. F. Lang, A. Brown, E. Brown, M. Cervantes, S. Macmullin, D. Masson, J. Schreiner, and H. Simgen, “A 220Rn source for the calibration of low-background experiments,”JINST11no. 04, (2016) P04004, arXiv:1602.01138 [physics.ins-det]

    Pith/arXiv arXiv 2016

  19. [19]

    SRIM - The stopping and range of ions in matter (2010),

    J. F. Ziegler, M. D. Ziegler, and J. P. Biersack, “SRIM - The stopping and range of ions in matter (2010),”Nucl. Instrum. Meth.B268(2010) 1818

    2010

  20. [20]

    Production and characterization of a 222Rn-emanating stainless steel source,

    F. Jörg, G. Eurin, and H. Simgen, “Production and characterization of a 222Rn-emanating stainless steel source,”Appl. Radiat. Isot.194(2023) 110666, arXiv:2205.15926 [physics.ins-det]

    arXiv 2023

  21. [21]

    The new CERN-ISOLDE on-line mass-separator facility at the PS-Booster,

    E. Kugler, D. Fiander, B. Johnson, H. Haas, A. Przewloka, H. Ravn, D. Simon, K. Zimmer, I. Collaboration,et al., “The new CERN-ISOLDE on-line mass-separator facility at the PS-Booster,”Nucl. Instrum. Methods Phys. Res. B70no. 1-4, (1992) 41–49

    1992

  22. [22]

    Production of 226Ra-implanted high-quality radon sources for detector characterization,

    F. Jörg, K. Blaum, C. Schweiger, and H. Simgen, “Production of 226Ra-implanted high-quality radon sources for detector characterization,” tech. rep., CERN, Geneva, 2023. http://cds.cern.ch/record/2845390

    arXiv 2023

  23. [23]

    Production and characterization of high-quality 226Ra-implanted sources for background mitigation studies in XENONnT experiment,

    M. Noia, “Production and characterization of high-quality 226Ra-implanted sources for background mitigation studies in XENONnT experiment,” Master thesis, University of Rome, Sapienza, 2024

    2024

  24. [24]

    E. W. Hoppeet al., “Use of electrodeposition for sample preparation and rejection rate prediction for assay of electroformed ultra high purity copper for 232Th and 238U prior to inductively coupled plasma mass spectrometry (ICP/MS),”J. Radioanal. Nucl. Chem.277 no. 1, (2008) 103–110

    2008

  25. [25]

    Reduction of radioactive backgrounds in electroformed copper for ultra-sensitive radiation detectors,

    E. W. Hoppe, C. E. Aalseth, O. T. Farmer, T. W. Hossbach, M. Liezers, H. S. Miley, N. R. Overman, and J. H. Reeves, “Reduction of radioactive backgrounds in electroformed copper for ultra-sensitive radiation detectors,”Nucl. Instrum. Meth. A764(2014) 116–121

    2014

  26. [26]

    Developing radiopure copper alloys for high strength low background applications,

    A. M. Suriano, S. M. Howard, C. D. Christofferson, I. J. Arnquist, and E. W. Hoppe, “Developing radiopure copper alloys for high strength low background applications,”AIP Conf. Proc.1921no. 1, (2018) 080001

    2018

  27. [27]

    Electrodeposition of adherent copper film on unmodified tungsten,

    C. Wang, J. Lei, C. Bjelkevig, S. Rudenja, N. Magtoto, and J. Kelber, “Electrodeposition of adherent copper film on unmodified tungsten,”Thin Solid Films445 no. 1, (2003) 72–79.https://www.sciencedirect. com/science/article/pii/S0040609003012392

    2003

  28. [28]

    Investigation of coating methods for radon background reduction in liquid xenon experiments,

    M. Piotter, “Investigation of coating methods for radon background reduction in liquid xenon experiments,” Bachelor’s thesis, University of Heidelberg, 2020

    2020

  29. [29]

    Magnetron sputtering,

    S. Swann, “Magnetron sputtering,”Physics in technology19no. 2, (1988) 67

    1988

  30. [30]

    https://www.europcoating.com/

    EC Europ Coating GmbH (now NTI NanoFilm). https://www.europcoating.com/. [online; accessed 29-December-2021]

    2021

  31. [31]

    Plasma spray-pvd: a new thermal spray process to deposit out of the vapor phase,

    K. V on Niessen and M. Gindrat, “Plasma spray-pvd: a new thermal spray process to deposit out of the vapor phase,”J. Therm. Spray Tech.20no. 4, (2011) 736–743

    2011

  32. [32]

    Laure Plasmatechnologie, Forschung, Entwicklung und Produktions GmbH

    Dr. Laure Plasmatechnologie, Forschung, Entwicklung und Produktions GmbH. http://laure-plasma.de/. [online; accessed 21-February-2022]

    2022

  33. [33]

    Growth, structure, and properties of plasma-deposited amorphous hydrogenated carbon–nitrogen films,

    D. Franceschini, “Growth, structure, and properties of plasma-deposited amorphous hydrogenated carbon–nitrogen films,” inAdvances in Plasma-Grown Hydrogenated Films, M. H. Francombe, ed., vol. 30 of Thin Films and Nanostructures, pp. 217–276. Academic Press, 2002

    2002

  34. [34]

    https://www.incosol4u.com/

    Innovative Coating Solutions SA. https://www.incosol4u.com/. [online; accessed 20-February-2022]

    2022

  35. [35]

    High rate thick film growth,

    J. A. Thornton, “High rate thick film growth,”Annu. Rev. Mater. Res.7no. 1, (1977) 239–260

    1977

  36. [36]

    Investigation of material coatings in order to reduce the emanation of radon,

    L. Fischer, “Investigation of material coatings in order to reduce the emanation of radon,” Bachelor’s thesis, University of Heidelberg, 2016

    2016

  37. [37]

    Investigation of coating-based radon barriers and studies towards their applicability in liquid xenon detectors,

    F. Jörg, “Investigation of coating-based radon barriers and studies towards their applicability in liquid xenon detectors,” Master’s thesis, University of Heidelberg, 2017. 10

    2017

  38. [38]

    Exploring the applicability of electrodeposited copper for reducing the radon background in liquid xenon detectors,

    M. Lecher, “Exploring the applicability of electrodeposited copper for reducing the radon background in liquid xenon detectors,” Bachelor’s thesis, University of Heidelberg, 2019

    2019

  39. [39]

    Mehrer,Diffusion in Solids, vol

    H. Mehrer,Diffusion in Solids, vol. 155. Springer Berlin Heidelberg, 2007

    2007

  40. [40]

    Algebraic approach to the radioactive decay equations,

    L. Moral and A. F. Pacheco, “Algebraic approach to the radioactive decay equations,”American Journal of Physics71no. 7, (07, 2003) 684–686

    2003

  41. [41]

    Self-annealing characterization of electroplated copper films,

    S. Lagrange, S. Brongersma, M. Judelewicz, A. Saerens, I. Vervoort, E. Richard, R. Palmans, and K. Maex, “Self-annealing characterization of electroplated copper films,”Microelectronic Engineering50no. 1, (2000) 449–457.https://www.sciencedirect.com/ science/article/pii/S0167931799003147

    2000