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arxiv: 2606.19007 · v1 · pith:EGJKOVAKnew · submitted 2026-06-17 · 🌌 astro-ph.IM

Characterisation of the NewAthena WFI's DEPFET Flight Production's Operational Parameters

L\'eonie Sommer , Johannes M\"uller-Seidlitz , Valentin Emberger , Robert Andritschke , Astrid Mayr , Annika Behrens , G\"unter Hauser , Peter Lechner
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Christian Sandow Anna Schweingruber Jonas P. Reiffers Elif Kutdemir \"Onc\"u
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Pith reviewed 2026-06-26 19:25 UTC · model grok-4.3

classification 🌌 astro-ph.IM
keywords DEPFETWide Field ImagerNewAthenaX-ray detectorsprototype sensorsenergy resolutionnoise reduction
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The pith

Tests on 64x64 DEPFET prototypes identify optimal parameters for NewAthena's flight detectors.

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

The paper describes how prototype sensors were used to explore the operational range of DEPFET pixels and to fine-tune ASIC and DEPFET settings. These settings include currents, voltages and read-out timing in rolling shutter mode. The optimizations lead to better energy resolution and lower noise. This work supports the preparation of the Large Detector Array for the Wide Field Imager on NewAthena.

Core claim

Prototype sensors of 64 by 64 pixels were used to analyse the sensor's operational range and to optimise the ASIC and DEPFET parameters i.e. current and voltage settings, as well as the DEPFET read-out timing parameters, resulting in an improved energy resolution, reduced noise and otherwise improved sensor characteristics.

What carries the argument

DEPFET pixels in rolling shutter mode, with parameter optimization through prototype testing to set currents, voltages and timing.

If this is right

  • Improved energy resolution for X-ray sources observed by the Wide Field Imager.
  • Reduced noise levels allowing better detection of faint signals.
  • Optimized settings applicable to the 2x2 array of 512x512 Large Detectors.
  • Support for 2 ms frame time across the 40 by 40 arcmin field of view.

Where Pith is reading between the lines

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

  • Verification on full-size detectors will be needed to confirm the parameter transfer.
  • Similar optimization approaches could apply to other DEPFET-based instruments.
  • The improved characteristics may enable new science cases for bright source observations with the Fast Detector.

Load-bearing premise

The results from small prototype sensors scale without major changes to the large flight detectors.

What would settle it

Energy resolution measurements on the actual flight Large Detectors using the reported parameters show no improvement compared to default settings.

Figures

Figures reproduced from arXiv: 2606.19007 by Anna Schweingruber, Annika Behrens, Astrid Mayr, Christian Sandow, Elif Kutdemir \"Onc\"u, G\"unter Hauser, Johannes M\"uller-Seidlitz, Jonas P. Reiffers, L\'eonie Sommer, Peter Lechner, Robert Andritschke, Valentin Emberger.

Figure 1
Figure 1. Figure 1: shows a 3D layout of one WFI pixel. When an X-ray photon hits the sensitive detector volume, electron-hole pairs are created, which are separated by a voltage applied over the sensor bulk. The holes are drained by the back contact, meanwhile the electrons are trapped in a potential well below the transistor gate called the internal gate and generate mirror charges in the transistor channel. The transistor … view at source ↗
Figure 2
Figure 2. Figure 2: Illustration of the DEPFET readout scheme with (green) and without (blue) collected electrons at the [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Front and back side of the prototype DEPFET module used for the characterisation. [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Column means of outermost left and right columns for the normalised event maps for different values of [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Noise [e−ENC] of all measurements for variations of VDS at ∼ −60 ◦C and ∼ −80 ◦C. Setting the voltage slightly above ensures that even with fluctuations the sensor’s performance with respect to the noise will stay excellent. 3.3 Variation of the source current The source current was indirectly probed by varying the gate on voltage VGate On. For proper DEPFET operation the gate off voltage and VVSSS have to… view at source ↗
Figure 6
Figure 6. Figure 6: shows the energy resolution (FWHM of the Mn-Kα peak) of all valid recombined events (so up to 2×2 pixels hit, and for multiple pixels the noise will increase compared to all valid single events). It can be seen that there are only minor improvements in noise and energy resolution once the drain-source current is greater than about 6 mA. For lower values, an increase in source current results in the degrada… view at source ↗
Figure 7
Figure 7. Figure 7: Fits through measurements (dark blue squares), limiting the operational window (white area). [PITH_FULL_IMAGE:figures/full_fig_p006_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Energy resolution FWHM for variation of VClear Gate Off and VClear Off. 3.5 Variation of the clear on voltage In the past, effects have been observed that are thought to stem from the Switcher-A ASIC emitting light for large differences between the clear on and clear off voltages. Therefore a variation of the clear on voltage is performed with constant clear off voltage to investigate the behaviour and fin… view at source ↗
Figure 9
Figure 9. Figure 9: Noise and energy resolution (FWHM of the Mn-K [PITH_FULL_IMAGE:figures/full_fig_p007_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Noise mean squared in [ADU2 ] for different exposure times (points) and linear fit through these points (line). This linear behaviour is consistent with the assumption that the decrease in sensor performance is caused by the Switcher-A starting to glow at high voltages. This is because charge carriers have to be continuously created for this linear behaviour to occur. As the parameters affecting the senso… view at source ↗
Figure 11
Figure 11. Figure 11: Left: OS current for different values of OS voltage, right: sensor temperature for different values of OS voltage. 3.7 Variation of the back contact voltage The back contact voltage is typically set to VBC = −90 V, same as the back contact inner guard ring varied in section 3.1. For this measurement, the back contact voltage was varied from −80 V to −114 V in steps of 5 V (where possible). The voltage of … view at source ↗
Figure 12
Figure 12. Figure 12: shows the energy spectrum around the Mn-Kα peak for the different values of VBC. It can be seen that there is no big difference in performance for the more positive values of VBC. For more negative values the energy resolution increases and the Mn-Kα peak is a lot wider and asymmetric with more counts registered for lower energies. This is due to the loss of charge carriers to the clear and therefore not … view at source ↗
Figure 13
Figure 13. Figure 13: Mean, minimum, and maximum value of the offset map for different [PITH_FULL_IMAGE:figures/full_fig_p010_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Mean, minimum, and maximum value of the offset map for different [PITH_FULL_IMAGE:figures/full_fig_p011_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: Clear correlation amplitude for different clear durations. 4.4 Variation of the settling 2 and clear duration simultaneously Lastly, settling 2 and the clear time were varied simultaneously in the interval of [100 ns, 1000 ns] in steps of 100 ns in a way that they were always set to the same value [PITH_FULL_IMAGE:figures/full_fig_p011_15.png] view at source ↗
Figure 16
Figure 16. Figure 16: Mean, minimum, and maximum value of the offset map for different [PITH_FULL_IMAGE:figures/full_fig_p012_16.png] view at source ↗
read the original abstract

NewAthena's Wide Field Imager (WFI) uses detectors made up from Depleted P-Channel Field Effect Transistor (DEPFET) pixels operated in rolling shutter mode. The Large Detector Array (LDA) contains a 2 $\times$ 2 array of 512 $\times$ 512 pixels Large Detectors (LDs) allowing for a field of view of 40' $\times$ 40' with a frame time of 2 ms while the 64 $\times$ 64 pixels Fast Detector (FD) can observe very bright X-ray sources due to a faster frame time of 0.08 ms. Prototype sensors (64 $\times$ 64 pixels) were used to analyse the sensor's operational range and to optimise the ASIC and DEPFET parameters i.e. current and voltage settings, as well as the DEPFET read-out timing parameters, resulting in an improved energy resolution, reduced noise and otherwise improved sensor characteristics.

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 on the characterization of operational parameters for the DEPFET sensors of the NewAthena Wide Field Imager (WFI). Using 64×64 pixel prototype sensors, the authors analyze the operational range and optimize ASIC and DEPFET parameters including current and voltage settings as well as readout timing parameters. This optimization is claimed to result in improved energy resolution, reduced noise, and other improved sensor characteristics for the flight hardware consisting of 512×512 pixel Large Detectors.

Significance. If the optimizations are shown to be valid for the full-size detectors, this work would be important for the successful operation of the WFI instrument on the NewAthena mission, providing the necessary parameter settings for the DEPFET flight production. The paper addresses a practical engineering need for the mission.

major comments (2)
  1. [Abstract] Abstract: The abstract claims that the optimizations on prototype sensors result in improved energy resolution and reduced noise, but supplies no quantitative data, error bars, methods details, or baseline comparisons, preventing evaluation of the central claim.
  2. [Abstract] Abstract: The transfer of optimized parameters from 64×64 prototypes to 512×512 flight Large Detectors is assumed without any discussion or data on scaling effects such as changes in total capacitance, row/column driver loading, or thermal gradients, which is load-bearing for the applicability to flight hardware.
minor comments (1)
  1. [Abstract] Abstract: The phrase 'otherwise improved sensor characteristics' is vague and should be specified if possible.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed review and constructive comments. We address each major comment below and will revise the manuscript to strengthen the presentation of results and applicability to flight hardware.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The abstract claims that the optimizations on prototype sensors result in improved energy resolution and reduced noise, but supplies no quantitative data, error bars, methods details, or baseline comparisons, preventing evaluation of the central claim.

    Authors: We agree that the abstract would benefit from quantitative support. The body of the manuscript contains the relevant measurements (energy resolution values, noise figures, and comparisons to unoptimized settings), but these were not summarized numerically in the abstract. In the revised version we will incorporate specific results, including achieved FWHM at Mn-Kα, noise reduction in electrons rms, and baseline comparisons, along with brief method references. revision: yes

  2. Referee: [Abstract] Abstract: The transfer of optimized parameters from 64×64 prototypes to 512×512 flight Large Detectors is assumed without any discussion or data on scaling effects such as changes in total capacitance, row/column driver loading, or thermal gradients, which is load-bearing for the applicability to flight hardware.

    Authors: The manuscript presents prototype results intended to define operational parameters for the flight production. We acknowledge that explicit discussion of scaling is absent. In revision we will add a dedicated paragraph in the introduction or conclusions section addressing the design rationale for transferability (identical pixel architecture, per-pixel current sources, and rolling-shutter timing independent of array size) while noting that full validation on 512×512 devices remains future work. No new scaling data will be added because none were acquired in this study. revision: yes

Circularity Check

0 steps flagged

No circularity; empirical characterization paper with no derivations or fitted predictions

full rationale

The manuscript reports experimental measurements on 64x64 prototype DEPFET sensors to determine operational ranges and optimize ASIC/DEPFET currents, voltages, and readout timing. No equations, first-principles derivations, or statistical predictions appear in the provided text. The central statements are direct empirical outcomes (improved energy resolution, reduced noise) from prototype testing; scaling assumptions to 512x512 flight devices are stated as context rather than derived results. No self-citations, ansatzes, or renamings of known results are load-bearing. This is a standard instrumentation characterization report whose claims rest on external measurement data, not internal redefinition.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no technical content available to identify free parameters, axioms, or invented entities.

pith-pipeline@v0.9.1-grok · 5763 in / 961 out tokens · 16761 ms · 2026-06-26T19:25:49.333027+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

14 extracted references

  1. [1]

    Silicon pore x-ray optics for the NewAthena telescope,

    Maximilien J. Collon et al., “Silicon pore x-ray optics for the NewAthena telescope,” in [Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds.,13093, 1309319, International Society for Optics and Photonics, SPIE (2024)

    2024

  2. [2]

    The hot and energetic universe: A white paper presenting the science theme moti- vating the athena+ mission,

    Kirpal Nandra et al., “The hot and energetic universe: A white paper presenting the science theme moti- vating the athena+ mission,” (2013)

    2013

  3. [3]

    VERITAS 2.2: a low noise source follower and drain current readout integrated circuit for the wide field imager on the Athena x-ray satellite,

    Herrmann, S., Koch, A., Obergassel, S., Treberspurg, W., Bonholzer, M., and Meidinger, N., “VERITAS 2.2: a low noise source follower and drain current readout integrated circuit for the wide field imager on the Athena x-ray satellite,” in [High Energy, Optical, and Infrared Detectors for Astronomy VIII], Holland, A. D. and Beletic, J., eds.,10709, 1070935...

    2018

  4. [4]

    The VERITAS 2.3 readout ASIC for the ATHENA Wide Field Imager,

    Schweingruber, A.-K., Herrmann, S., Orel, P., Dakshinamurthy, A. K., Mayr, A., M¨ uller-Seidlitz, J., Reiffers, J., Albrecht, S., Schnetler, H., Allen, S. W., and Morris, G., “The VERITAS 2.3 readout ASIC for the ATHENA Wide Field Imager,” in [Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray], den Herder, J.-W. A., Nikzad, S., and Nakaz...

    2024

  5. [5]

    (in preparation, 2027)

    Kirpal Nandra et al. (in preparation, 2027)

    2027

  6. [6]

    The Wide Field Imager for the NewAthena mission: preliminary design and verification,

    Antonelli, V., Pietschner, D., Strecker, R., Mican, B., M¨ oller, J. P., S¨ onmez, A., Saraf, A., Schnetler, H., and Nandra, P., “The Wide Field Imager for the NewAthena mission: preliminary design and verification,” in [Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds.,13093, 13...

    2024

  7. [7]

    Spectral performance budget for ATHENA’s Wide Field Imager,

    Mayr, A., M¨ uller-Seidlitz, J., Emberger, V., Andritschke, R., Reiffers, J., Schweingruber, A., Albrecht, S., and Schnetler, H., “Spectral performance budget for ATHENA’s Wide Field Imager,” in [Modeling, Systems Engineering, and Project Management for Astronomy XI], Egner, S. E. and Roberts, S., eds.,13099, 130992E, International Society for Optics and ...

    2024

  8. [8]

    Spectroscopic performance of detectors for Athena’s WFI: measurements and simulation,

    M¨ uller-Seidlitz, J., Andritschke, R., Emberger, V., Bonholzer, M., Hauser, G., Lechner, P., Mayr, A., Reiffers, J., Schweingruber, A., and Treberspurg, W., “Spectroscopic performance of detectors for Athena’s WFI: measurements and simulation,” in [Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray], den Herder, J.-W. A., Nikzad, S., and...

    2024

  9. [9]

    Private communication

    WFI consortium. Private communication

  10. [10]

    A megahertz active pixel sensor for x-ray astronomy,

    M¨ uller-Seidlitz, J., “A megahertz active pixel sensor for x-ray astronomy,” (January 2020)

    2020

  11. [11]

    Roan, a root based analysis framework,

    Lauf, T. and Andritschke, R., “Roan, a root based analysis framework,” (2013)

    2013

  12. [12]

    Achievable noise performance of spectroscopic prototype depfet detectors,

    Treberspurg, W., Meidinger, N., M¨ uller-Seidlitz, J., and Herrmann, S., “Achievable noise performance of spectroscopic prototype depfet detectors,”Journal of Instrumentation13, P12001 (December 2018)

    2018

  13. [13]

    Achievable time resolution of spectroscopic prototype depfet detectors,

    Treberspurg, W., Hauser, G., Meidinger, N., M¨ uller-Seidlitz, J., and Ott, S., “Achievable time resolution of spectroscopic prototype depfet detectors,”Journal of Instrumentation14, P03019 (March 2019)

    2019

  14. [14]

    Low-temperature proton irradiation with DEPFETs for Athena’s wide field imager,

    Emberger, V., Andritschke, R., Azhdarzadeh, P., Hauser, G., Mayr, A., M¨ uller-Seidlitz, J., Rezaei, A., and Treberer-Treberspurg, W., “Low-temperature proton irradiation with DEPFETs for Athena’s wide field imager,” in [Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray], den Herder, J.-W. A., Nikzad, S., and Nakazawa, K., eds.,13093, 13...

    2024