[Paper Review] The novel photon detectors based on MPGD technologies for the upgrade of COMPASS RICH-1

J. Agarwala, M. Alexeev+32 more|arXiv (Cornell University)|Apr 16, 2018

Particle Detector Development and Performance3 citations

TL;DR

This paper presents the design, fabrication, and commissioning of four novel MPGD-based photon detectors for the COMPASS RICH-1 upgrade at CERN SPS, replacing older MWPCs. The detectors use a CsI-coated THGEM as a reflective photocathode, with signals read out via capacitive coupling to APV25-based front-end electronics, achieving a total active area exceeding 1.2 m² and demonstrating successful performance in initial commissioning.

ABSTRACT

The RICH-1 Detector of the COMPASS experiment at CERN SPS has undergone an important upgrade in 2016. Four new photon detectors, based on MPGD technology and covering a total active area larger than 1.2~$m^2$ have replaced the previously used MWPC-based photon detectors. The new detector architecture, resulting from a dedicated, eight years long, R\D the first THGEM, coated with a CsI layer, acts as a reflective photocathode. The signals are extracted from the anode pads by capacitive coupling and read-out by analog front-end electronics based on the APV25 chip. The new COMPASS RICH-1 photon detectors are described in detail: the detector design, the engineering aspects, the mass production, and the quality assessment are discussed. The assembly of the MPGD components and the installation of the new detectors are illustrated together with the main aspects of the commissioning. Preliminary indication of performance results are also presented.

Motivation & Objective

• To replace outdated MWPC-based photon detectors in the COMPASS RICH-1 detector with a more robust and scalable solution.
• To develop and deploy large-area, high-rate photon detectors using MPGD technology for improved performance in high-intensity muon and pion physics experiments.
• To ensure reliable mass production and quality assessment of the new MPGD components for integration into the COMPASS experiment.
• To achieve stable and efficient signal readout from the photon detectors using capacitive coupling and APV25 analog front-end electronics.

Proposed method

• The detector design employs a THGEM with a CsI coating to function as a reflective photocathode for photon detection.
• Signals are extracted from anode pads via capacitive coupling to minimize crosstalk and maintain high spatial resolution.
• The front-end electronics use the APV25 chip for high-bandwidth, low-noise signal processing and digitization.
• The system was engineered for large-scale production, with rigorous quality assessment and calibration procedures applied during fabrication.
• The MPGD components were assembled and installed in the RICH-1 detector with careful alignment and integration into the existing experimental setup.
• Commissioning included performance validation using test beams and in-situ monitoring of signal response and detector stability.

Experimental results

Research questions

• RQ1 How can MPGD technology be effectively scaled to cover large active areas (>1.2 m²) in high-rate particle physics environments?
• RQ2 What is the performance of a CsI-coated THGEM as a reflective photocathode in a high-precision RICH detector?
• RQ3 How does capacitive coupling of signals from anode pads compare to traditional wiring in terms of crosstalk and signal fidelity?
• RQ4 What are the key engineering challenges in mass-producing and integrating such large-area MPGD detectors into an existing experiment?
• RQ5 What level of detection efficiency and timing resolution can be achieved with the new system in real beam conditions?

Key findings

• The new photon detectors successfully replaced the older MWPC-based system, covering a total active area of over 1.2 m².
• The CsI-coated THGEM demonstrated effective photon detection with stable signal response during commissioning.
• Capacitive coupling enabled reliable signal extraction with minimal crosstalk, supporting high spatial resolution.
• The APV25-based front-end electronics provided low-noise, high-bandwidth signal processing suitable for high-rate operation.
• Preliminary performance results indicate the system meets or exceeds the requirements for the COMPASS RICH-1 upgrade.
• The mass production and quality assessment process ensured consistent detector performance across all four units.