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

TL;DR

This paper presents the development and implementation of new MPGD-based photon detectors for the COMPASS RICH-1 upgrade, highlighting design, production, and preliminary performance results.

Contribution

It introduces a novel hybrid MPGD detector architecture with a CsI-coated THGEM and Micromegas, developed over eight years for enhanced photon detection in RICH-1.

Findings

Successful assembly and installation of the new detectors

Preliminary performance indicators show promising results

Enhanced photon detection capabilities compared to previous MWPC-based detectors

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 program, consists in a hybrid MPGD combination of two THGEMs and a Micromegas stage; 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.