Novel MPGD based detectors of single photons in COMPASS RICH-1

Abstract

COMPASS is a fixed target experiment at CERN SPS aimed to study Hadron Structure and Spectroscopy. Hadron Identification in the momentum range between 3 and 55 GeV/c is provided by a large gaseous Ring Imaging Cherenkov Counter (RICH-1). To cope with the challenges imposed by the new physics program of COMPASS, RICH-1 have been upgraded by replacing four MWPCs based photon detectors with newly developed MPGD based photon detectors. The architecture of the novel detectors is a hybrid combination of two layers of THGEMs and a MicroMegas. The top of the first THGEM is coated with CsI acting as a reflective photo-cathode. The anode is segmented in pads capacitively coupled to the APV-25 based readout. The new hybrid detectors have been commissioned during 2016 COMPASS data taking and stably operated during 2017 run. In this paper all aspects of the novel photon detectors for COMPASS RICH-1 are discussed.

Systematic investigation of critical charge limits in Thick GEMs

“…Therefore, a dedicated post-production treatment is necessary in order to smooth out the hole edges and remove defects or other imperfections coming from the drilling of the holes. An effective polishing and cleaning procedure has been proposed in [7] and implemented successfully in the COMPASS RICH-1 upgrade project [8,9].…”

Single Electron Spectra in RPWELL-based detectors

“…In this context, Gaseous Photo-detectors [6] employing Multiwire [10] and Drift [11] Chambers, Multi-step avalanche chambers [12], cascaded GEMs [13][14][15] and THGEM-based [16][17][18][19] detectors have been playing an important role in experiments. As demonstrated in [20], the more recent "hybrid" CsI-coated THGEM-Micromegas has shown to be an efficient upgrade for the COMPASS-RICH-I. Furthermore, THGEM-based detectors were demonstrated to have moderate (sub-millimeter) localization resolution [21] and about 10 nsec time resolution, which comply with the requirements in most RICH devices.…”

Single-electron spectra in RPWELL-based detectors

“…In this context, Gaseous Photodetectors [6] employing Multiwire [10] and Drift [11] Chambers, Multi-step avalanche chambers [12], cascaded GEMs [13][14][15] and THGEM-based [16][17][18][19] detectors have been playing an important role in experiments. As demonstrated in [20], the more recent "hybrid" CsI-coated THGEM-Micromegas has shown to be an efficient upgrade for the COMPASS-RICH-I. Furthermore, THGEM-based detectors were demonstrated to have moderate (sub-millimeter) localization resolution [21] and about 10 nsec time resolution, which comply with the requirements of most RICH devices.…”