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arxiv: 1907.02385 · v1 · pith:ABDNJNUZnew · submitted 2019-07-04 · ⚛️ physics.ins-det · hep-ex· nucl-ex

The high voltage system with pressure and temperature corrections for the novel MPGD-based photon detectors of COMPASS RICH-1

J. Agarwala , M. Bari , F. Bradamante , A. Bressan , C. Chatterjee , A. Cicuttin , P. Ciliberti , M. Crespo
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S. Dalla Torre S. Dasgupta B. Gobbo M. Gregori G. Hamar S. Levorato A. Martin G. Menon L.B. Rizzuto Triloki F. Tessarotto Y. X. Zhao
This is my paper

Pith reviewed 2026-05-25 08:50 UTC · model grok-4.3

classification ⚛️ physics.ins-det hep-exnucl-ex
keywords MPGDThick-GEMMicroMegashigh voltage systemgain stabilitypressure compensationCOMPASS RICH-1photon detector
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The pith

A voltage compensation system automatically adjusts biasing voltages in hybrid MPGD photon detectors to maintain constant gain despite pressure and temperature changes.

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

The paper presents the high-voltage control architecture for the large hybrid MPGD photon detectors installed in COMPASS RICH-1 since 2016. These detectors combine two layers of Thick-GEMs with a resistive MicroMegas, requiring coordinated biasing of more than 20,000 segmented electrodes through over 100 channels. A custom software layer on commercial supplies enforces voltage correlations, logs data at 1 Hz, and protects against operator or detector faults. The central development is an automatic compensation routine that recalculates and applies the correct voltages from measured pressure and temperature to hold gas gain fixed throughout data taking. This addresses the general stability requirement for multi-layer gaseous detectors where environmental drifts would otherwise degrade performance.

Core claim

The voltage compensation system automatically adjusts the biasing voltage according to environmental pressure and temperature variations to achieve constant gain over time in the novel MPGD-based photon detectors.

What carries the argument

The custom software package that implements real-time voltage compensation from pressure and temperature sensors and distributes the corrected set-points across the segmented Thick-GEM and MicroMegas electrodes while preserving required inter-electrode correlations.

If this is right

  • Detector gain remains stable across multi-month COMPASS runs without manual voltage retuning.
  • The same compensation logic preserves the required voltage ratios among the ten different electrode types during environmental excursions.
  • Real-time 1 Hz monitoring combined with compensation allows automatic protection against discharge-induced voltage excursions.
  • The approach satisfies the general need for gain stability in any multi-layer gaseous detector operated over long periods.

Where Pith is reading between the lines

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

  • The method could be ported to other RICH or tracking detectors that use similar Thick-GEM plus MicroMegas stacks and face comparable environmental drift.
  • Because the correction uses only commercial supplies and a software overlay, the same architecture scales to larger detector systems with thousands of channels.
  • If the correction function proves portable across different gas mixtures, it would reduce calibration overhead for future gaseous photon detectors.

Load-bearing premise

The gain response of the hybrid MPGD stack to pressure and temperature can be captured by a sufficiently accurate and stable correction function that does not itself introduce new instabilities or require frequent re-tuning during data taking.

What would settle it

A period of physics data taking in which measured detector gain changes by more than the target tolerance even while the compensation system is active and pressure and temperature are recorded.

Figures

Figures reproduced from arXiv: 1907.02385 by A. Bressan, A. Cicuttin, A. Martin, B. Gobbo, C. Chatterjee, F. Bradamante, F. Tessarotto, G. Hamar, G. Menon, J. Agarwala, L.B. Rizzuto, M. Bari, M. Crespo, M. Gregori, P. Ciliberti, S. Dalla Torre, S. Dasgupta, S. Levorato, Triloki, Y. X. Zhao.

Figure 1
Figure 1. Figure 1: Sketch of the hybrid single photon detector: two staggered THGEM layers are coupled to a bulk MicroMegas. The drift wire and the [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Pictures showing two units (600×300 mm2 ) of MMs (top picture) and THGEMs (bottom picture) in one single detector (600×600 mm2 ). a pad segmented anode, where the pad size is 7.5×7.5 mm2 with 8 mm pitch. Each hybrid 600×600 mm2 detector is built by two 600×300 mm2 units arranged side by side within a single detector, as shown in [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: (Color online) The resistive MM by discrete elements. (a)Sketch of the PCB layers illustrating the principle of readout design. The blue [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Scheme of the voltage distribution of the top (bottom) face of a THGEM sector containing 6 segments. [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Calculation of the electric field configuration at the lateral edges of the detector before introducing the auxiliary electrodes. (a) THGEM [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Block diagram showing how the data is read out from sensors. [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Picture of the PCB housing the pressure and temperature sensors. [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Gain curve of a THGEM with the geometrical parameters reported in Sec. 2 operated in Ar:CH [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Gain curve of a MicroMegas with the geometrical parameters reported in Sec. 2 operated in Ar:CH [PITH_FULL_IMAGE:figures/full_fig_p009_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Gain dependence on the pressure. The working gas is Ar:CH [PITH_FULL_IMAGE:figures/full_fig_p009_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: Block diagram of the hybrid high voltage control system, showing the components and their communication channels. [PITH_FULL_IMAGE:figures/full_fig_p010_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: Screen shot of the main frame of the graphical interface, providing information on all the detector sectors, the spark counts, and details [PITH_FULL_IMAGE:figures/full_fig_p013_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Example of amplitude spectrum obtained applying the data selection explained in the text. The amplitude units are ADC channels, [PITH_FULL_IMAGE:figures/full_fig_p014_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: the standard deviation of the distribution is less than 5%, proving the robustness of the estimator. [PITH_FULL_IMAGE:figures/full_fig_p015_14.png] view at source ↗
Figure 14
Figure 14. Figure 14: Estimated gain using the gain estimator G for 75 independent samples of data collected in conditions that ensure approximately constant [PITH_FULL_IMAGE:figures/full_fig_p016_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: Correlation of the current sparks among three multiplication stages. A marker in the top (middle) row illustrates a current spark in the [PITH_FULL_IMAGE:figures/full_fig_p017_15.png] view at source ↗
Figure 16
Figure 16. Figure 16: Gain in the sectors of the hybrid detectors. Every four points belong to one hybrid detector, corresponding to four sectors for each [PITH_FULL_IMAGE:figures/full_fig_p017_16.png] view at source ↗
Figure 17
Figure 17. Figure 17: (Left)∆V (unit V) of sector 1 of the first THGEM in one particular detector as a function of correction factor. The red line is a linear fit to the data points. (right) The residual of the data points and the linear fit in the left plot. data using the estimator G discussed in Sec. 7.1. Two sets of data per day are used to monitor the gain stability, one collected in the early morning and the other one in… view at source ↗
Figure 18
Figure 18. Figure 18: Temperature (first plot from the top), pressure (second plot from the top), the corresponding correction factor (third plot from the top) [PITH_FULL_IMAGE:figures/full_fig_p019_18.png] view at source ↗
read the original abstract

The novel MPGD-based photon detectors of COMPASS RICH-1 consist of large-size hybrid MPGDs with multi-layer architecture including two layers of Thick-GEMs and a bulk resistive MicroMegas. The top surface of the first THGEM is coated with a CsI film which also acts as photo-cathode. These detectors have been successfully in operation at COMPASS since 2016. Concerning bias-voltage supply, the Thick-GEMs are segmented in order to reduce the energy released in case of occasional discharges, while the MicroMegas anode is segmented into pads individually biased with positive voltage while the micromesh is grounded. In total, there are about ten different electrode types and more than 20000 electrodes supplied by more than 100 HV channels, where appropriate correlations among the applied voltages are required for the correct operation of the detectors. Therefore, a robust control system is mandatory, implemented by a custom designed software package, while commercial power supply units are used. This sophisticated control system allows to protect the detectors against errors by the operator, to monitor and log voltages and currents at 1 Hz rate, and automatically react to detector misbehaviour. In addition, a voltage compensation system has been developed to automatically adjust the biasing voltage according to environmental pressure and temperature variations, to achieve constant gain over time. This development answers to a more general need. In fact, voltage compensation is always a requirement for the stability of gaseous detectors and its need is enhanced in multi-layer ones. In this paper, the HV system and its performance are described in details, as well as the stability of the novel MPGD-based photon detectors during the physics data taking at COMPASS.

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 / 1 minor

Summary. The paper describes the high-voltage biasing and control infrastructure for the hybrid MPGD photon detectors (two THGEM layers plus resistive MicroMegas) installed in COMPASS RICH-1. It details electrode segmentation for discharge protection, the requirement for correlated voltages across >20 000 electrodes supplied by >100 channels, a custom software package for monitoring, logging, protection and automatic response, and a pressure/temperature-based voltage compensation scheme intended to keep the detector gain constant. The manuscript asserts successful operation since 2016 and presents the system as a solution to the general stability problem of multi-layer gaseous detectors.

Significance. If the compensation scheme demonstrably maintains gain stability, the work supplies a concrete, field-tested engineering solution for a recurring operational challenge in large gaseous detectors. The detailed description of segmentation strategy, inter-electrode voltage correlations, and software logic could serve as a reusable reference for future MPGD or multi-layer gaseous systems.

major comments (1)
  1. [Abstract] Abstract and performance description: the central claim that the P/T compensation system achieves constant gain and that the detectors have operated successfully since 2016 is presented without any quantitative performance metrics (gain vs. time, before/after compensation comparisons, RMS stability figures, or error budgets). This absence is load-bearing for the paper's main engineering assertion.
minor comments (1)
  1. The text would benefit from an explicit table listing the ten electrode types, their nominal voltages, and the required correlation rules enforced by the control software.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive evaluation of the work's significance and for the constructive comment on the abstract and performance claims. We address the point below.

read point-by-point responses

  1. Referee: [Abstract] Abstract and performance description: the central claim that the P/T compensation system achieves constant gain and that the detectors have operated successfully since 2016 is presented without any quantitative performance metrics (gain vs. time, before/after compensation comparisons, RMS stability figures, or error budgets). This absence is load-bearing for the paper's main engineering assertion.

    Authors: We agree that the absence of quantitative metrics weakens the central engineering claim. The current manuscript text focuses on the system architecture, segmentation strategy, software logic, and the principle of the P/T compensation, while stating successful operation since 2016 without supporting numbers. In the revised manuscript we will add a dedicated performance section (or subsection) containing: (i) a time series of monitored gain (or equivalent current) over representative running periods, (ii) direct before/after compensation comparisons, (iii) RMS stability figures extracted from the 1 Hz logging data, and (iv) a concise error budget that accounts for the dominant environmental and HV-channel uncertainties. These additions will be referenced from the abstract. revision: yes

Circularity Check

0 steps flagged

No circularity; purely descriptive engineering account

full rationale

The paper is a technical description of an HV supply, segmentation, control software, and P/T compensation system for COMPASS RICH-1 MPGD detectors. No derivation chain, first-principles result, fitted parameter renamed as prediction, or uniqueness theorem is claimed. The compensation is presented as an implemented engineering solution whose performance is reported via monitoring logs; nothing reduces to its own inputs by construction. Self-contained against external benchmarks of detector operation.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

This is an engineering description of an implemented control system; no free parameters, mathematical axioms, or new physical entities are introduced or fitted.

pith-pipeline@v0.9.0 · 5944 in / 1064 out tokens · 36673 ms · 2026-05-25T08:50:16.850117+00:00 · methodology

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Reference graph

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