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arxiv: 2606.03295 · v1 · pith:AHQTPJ4Znew · submitted 2026-06-02 · ⚛️ physics.ins-det

GEM Production at the FTD in Bonn

Philip Hauer , Markus Ball , Shania M\"uller , Dmitri Schaab , Tim Sch\"uttler , Rui De Oliviera , Adam Drozd , Alexis Rodrigues
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Bernhard Ketzer
This is my paper

Pith reviewed 2026-06-28 08:07 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords GEM foilsGas Electron Multiplierphotolithographychemical etchingquality controlleakage currentdetector productiongaseous detectors
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The pith

The FTD in Bonn has set up a production line for 10 cm x 10 cm GEM foils that achieves uniform hole sizes and leakage currents below 1 nA at 600 V.

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

This paper reports the creation of a local fabrication process for Gas Electron Multiplier foils at the Forschungs- und Technologiezentrum Detektorphysik. The method applies double-mask photolithography to copper-clad polyimide sheets and uses chemical etching to form holes with 70 μm outer and 50 μm inner diameters. Quality checks via optical imaging and high-voltage testing confirm uniform hole distributions and currents under 1 nA with no discharge sites. A reader would care because the work shows that a university facility can now supply functional amplification foils for gaseous detectors without relying on external sources.

Core claim

The fabrication process utilizing a double-mask photolithographic technique on 50 μm polyimide cladded on both sides with 5 μm copper, together with the chemical etching procedure that achieves uniform hole geometries with outer hole diameters of 70 μm and inner hole diameters of 50 μm, combined with semi-automated optical inspection and high-voltage leakage current tests, produces foils with uniform hole size distributions and leakage currents of less than 1 nA at 600 V in air with no discharge hotspots, confirming that the production chain is capable of delivering high-performance foils suitable for research and development purposes.

What carries the argument

Double-mask photolithographic technique followed by chemical etching to control hole diameters on copper-clad polyimide, validated by optical inspection and high-voltage leakage testing.

If this is right

  • The production chain can supply GEM foils that meet the performance requirements for gaseous detectors.
  • Local fabrication removes dependence on distant suppliers for small-scale R&D quantities.
  • The same process supports repeated production runs for detector prototyping.
  • Quality protocols provide a repeatable way to verify foil suitability before detector assembly.

Where Pith is reading between the lines

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

  • The established line could be used to test variations in hole geometry or substrate thickness for specific detector applications.
  • If scaled, the method might reduce turnaround time for custom foil designs in ongoing experiments.
  • Combining these foils with other locally produced detector elements could simplify full detector construction at the same site.

Load-bearing premise

The chemical etching procedure will reliably produce the target outer hole diameter of 70 μm and inner hole diameter of 50 μm with sufficient uniformity across the 10 cm x 10 cm foil area without post-etch adjustments or high failure rates.

What would settle it

Measuring leakage currents above 1 nA at 600 V or observing non-uniform hole sizes or discharge hotspots during quality control on multiple produced foils would show the production chain does not deliver the claimed performance.

Figures

Figures reproduced from arXiv: 2606.03295 by Adam Drozd, Alexis Rodrigues, Bernhard Ketzer, Dmitri Schaab, Markus Ball, Philip Hauer, Rui De Oliviera, Shania M\"uller, Tim Sch\"uttler.

Figure 1
Figure 1. Figure 1: Production process for GEM foils. 3 [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: A schematic view of the clean room infrastructure at the FTD. [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: The wet bench for the etching steps. is not light-sensitive anymore. The wet-bench is equipped with a cascaded overflow rinser where clean DI water flows into the left beaker, from which it flows into the middle beaker once the left beaker is full and so it continues. In between each etching process, the foil is placed in the rinser and is also thoroughly sprayed with DI water to ensure that no chemicals a… view at source ↗
Figure 4
Figure 4. Figure 4: The Spark Detection System (SDS) with an unframed GEM foil. [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Outer hole size distribu￾tion [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: Leakage current mea￾surement of foil 07 at 650 V [PITH_FULL_IMAGE:figures/full_fig_p011_7.png] view at source ↗
Figure 9
Figure 9. Figure 9: Spark map of foil 07, with only one spark in total [PITH_FULL_IMAGE:figures/full_fig_p011_9.png] view at source ↗
read the original abstract

This manuscript describes the establishment of a local production line for 10 cm x 10 cm Gas Electron Multiplier (GEM) foils at the Forschungs- und Technologiezentrum Detektorphysik (FTD) at the university of Bonn. GEM foils are widely used in modern gaseous detectors, providing high-gain signal amplification and high-rate capability. Our fabrication process utilizes a double-mask photolithographic technique on 50 $\mu$m polyimide cladded on both sides with 5 $\mu$m copper. The chemical etching procedure that is required to achieve uniform hole geometries with outer hole diameters of 70 $\mu$m and inner hole diameters of 50 $\mu$m will be described. Quality control protocols, including semi-automated optical inspection and high-voltage leakage current tests, demonstrate that foils produced at our facility achieve uniform hole size distributions and leakage currents of less than 1 nA at 600 V in air with no discharge hotspots. These results confirm that the production chain is capable of delivering high-performance foils suitable for research and development purposes.

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 / 0 minor

Summary. The manuscript describes the establishment of a local production line for 10 cm × 10 cm GEM foils at the FTD in Bonn. It details a double-mask photolithographic process on 50 μm polyimide with 5 μm copper cladding and the chemical etching steps needed to reach target outer/inner hole diameters of 70/50 μm. Quality-control results from semi-automated optical inspection and high-voltage leakage tests are reported to show uniform hole-size distributions together with leakage currents below 1 nA at 600 V in air and no discharge hotspots, leading to the conclusion that the facility can supply high-performance foils for R&D use.

Significance. If the quantitative QC data are supplied and shown to be reproducible, the work would be useful to the detector community by documenting an accessible European source of GEM foils and by making the process parameters available for replication or adaptation in other R&D settings.

major comments (1)
  1. [Quality-control / Results description] The quality-control results (optical inspection and HV leakage measurements) are stated only qualitatively in the abstract and process description; no hole-diameter histograms, standard deviations, number of foils or holes sampled, or comparison with commercial reference foils are provided. This absence prevents assessment of whether the claimed uniformity and <1 nA leakage performance are statistically supported.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback. We agree that the quality-control section requires quantitative data to support the claims of uniformity and low leakage, and we will revise the manuscript to include the requested details.

read point-by-point responses

  1. Referee: [Quality-control / Results description] The quality-control results (optical inspection and HV leakage measurements) are stated only qualitatively in the abstract and process description; no hole-diameter histograms, standard deviations, number of foils or holes sampled, or comparison with commercial reference foils are provided. This absence prevents assessment of whether the claimed uniformity and <1 nA leakage performance are statistically supported.

    Authors: We acknowledge that the current manuscript presents the QC results only qualitatively. In the revised version we will add hole-diameter histograms (with mean, standard deviation and sample size), specify the number of foils and holes inspected, report the number of foils tested for leakage current, and include a direct comparison to commercial reference foils using the same measurement protocols. These additions will provide the statistical basis for the stated performance. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

This is a purely experimental methods paper describing a GEM foil fabrication process and associated quality-control measurements. No equations, derivations, fitted parameters, or model-based predictions appear anywhere in the text. The central claims rest directly on reported optical inspection data and leakage-current test results, which are independent measurements rather than reductions of any prior input by construction. No self-citations, uniqueness theorems, or ansatzes are invoked. The work is therefore self-contained against external benchmarks and receives the default non-circularity finding.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No free parameters, axioms, or invented entities; the paper is an experimental methods report relying on standard photolithography and etching assumptions from prior GEM literature.

pith-pipeline@v0.9.1-grok · 5744 in / 999 out tokens · 16599 ms · 2026-06-28T08:07:49.384834+00:00 · methodology

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Reference graph

Works this paper leans on

10 extracted references · 6 canonical work pages · 2 internal anchors

  1. [1]

    GEM: A new concept for electron amplification in gas de- tectors

    F. Sauli. “GEM: A new concept for electron amplification in gas de- tectors”. In:Nucl. Instrum. Meth. A386 (1997), pp. 531–534.doi: 10.1016/S0168-9002(96)01172-2

    work page doi:10.1016/s0168-9002(96)01172-2 1997

  2. [2]

    The upgrade of the ALICE TPC with GEMs and continuous readout

    J. Adolfsson et al. “The upgrade of the ALICE TPC with GEMs and continuous readout”. In:JINST16.03 (2021), P03022.doi:10.1088/ 1748-0221/16/03/P03022. arXiv:2012.09518 [physics.ins-det]

    arXiv 2021

  3. [3]

    Development of the CMS detector for the CERN LHC Run 3

    Aram Hayrapetyan et al. “Development of the CMS detector for the CERN LHC Run 3”. In:JINST19.05 (2024), P05064.doi:10.1088/ 1748-0221/19/05/P05064. arXiv:2309.05466 [physics.ins-det]

    arXiv 2024

  4. [4]

    Construction, test and commissioning of the triple- GEM tracking detector for COMPASS

    C. Altunbas et al. “Construction, test and commissioning of the triple- GEM tracking detector for COMPASS”. In:Nucl. Instrum. Meth. A 490 (2002), pp. 177–203.doi:10.1016/S0168-9002(02)00910-5

    work page doi:10.1016/s0168-9002(02)00910-5 2002

  5. [5]

    Progress on large area GEMs (VCI 2010)

    Marco Villa et al. “Progress on large area GEMs”. In:Nucl. Instrum. Meth. A628 (2011). Ed. by Thomas Bergauer et al., pp. 182–186.doi: 10.1016/j.nima.2010.06.312. arXiv:1007.1131 [physics.ins-det]

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1016/j.nima.2010.06.312 2011

  6. [7]

    Micromegas in a bulk

    I. Giomataris et al. “Micromegas in a bulk”. In:Nucl. Instrum. Meth. A560 (2006), pp. 405–408.doi:10 . 1016 / j . nima . 2005 . 12 . 222. arXiv:physics/0501003

    Pith/arXiv arXiv 2006

  7. [8]

    A floating multi-channel picoammeter for mi- cropattern gaseous detector current monitoring

    A. Utrobicic et al. “A floating multi-channel picoammeter for mi- cropattern gaseous detector current monitoring”. In:Nucl. Instrum. Meth. A801 (2015), pp. 21–26.doi:10.1016/j.nima.2015.08.021

    work page doi:10.1016/j.nima.2015.08.021 2015

  8. [9]

    Development of a Spark-Detection System for the Qual- ity Assurance of Large-Area GEM-Foils

    M. Ball et al. “Development of a Spark-Detection System for the Qual- ity Assurance of Large-Area GEM-Foils”. In:J. Phys. Conf. Ser.1498 (2020). Ed. by Paul Colas, Theopisti Dafni, and Esther Ferrer Ribas, p. 012056.doi:10.1088/1742-6596/1498/1/012056

    work page doi:10.1088/1742-6596/1498/1/012056 2020

  9. [10]

    Study of long-term sustained operation of gaseous detectors for the high rate environment in CMS

    Jeremie Alexandre Merlin. “Study of long-term sustained operation of gaseous detectors for the high rate environment in CMS”. PhD thesis. Strasbourg U., Apr. 2016

    2016

  10. [11]

    Optical quality assurance of GEM foils

    T. Hild´ en et al. “Optical quality assurance of GEM foils”. In:Nucl. Instrum. Meth. A770 (2015), pp. 113–122.doi:10.1016/j.nima. 2014.10.015. arXiv:1704.06691 [physics.ins-det]. 13

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1016/j.nima 2015