Evolution and Recent Developments of the Gaseous Photon Detectors Technologies

The evolution and the present status of the gaseous photon detectors technologies are reviewed. The most recent developments in several branches of the field are described, in particular the installation and commissioning of the first large area MPGD-based detectors of single photons on COMPASS RICH-1. Investigation of novel detector architectures, different materials and various applications are reported, and the quest for visible light gaseous photon detectors is discussed. The progress on the use of gaseous photon detector related techniques in the field of cryogenic applications and gaseous or liquid scintillation imaging are presented.Comment: NDIP 2017 Proceedings, review, submitted to Nuc. Inst. Methods

THGEM: A fast growing MPGD technology

Thick-GEMs (THGEMs) are simple and robust gaseous multipliers, derived from the GEM design and proposed for large-scale applications. Classical THGEMs consist of Printed Circuit Boards (PCBs) with a regular pattern of holes obtained by drilling; they are manufactured by industry in large series and large size; their response for different geometrical parameters and operational conditions has been extensively studied. Different substrates (ceramic, glass, PTFE, etc.) and various production procedures have also been investigated with promising results. Different design options, like highly segmented electrodes, and different architectures, in particular those based on the Thick-WELL design are being actively studied. THGEMs are used as gaseous multipliers and as reflective photocathodes for VUV photons when coated with a CsI layer. THGEM-based Photon Detectors have been successfully implemented in 2016 on COMPASS RICH-1 for a total active area of 1.4 m2. Applications of THGEM (also called LEM) technology in the field of cryogenic detectors, in particular for double-phase large volume Ar ones are proposed. The recently discovered phenomenon of bubble assisted electro-luminescence in liquid Xe opens the way to local dual phase cryogenic detector configurations when using THGEMs. The detection of X-rays and neutrons using THGEM-based devices is a very active field. Promising results have been obtained using THGEMs for imaging applications

Summary of Section “New Accelerators, Detectors, Calculus and New Technologies”

Deployment and development of advanced technologies for accelerators, detectors, electronics and computing is inherent in everyday activity of all research projects and experiments funded by INFN. However, when a part of the research work can be clearly identified as an R&D activity aimed at the development of a new technology or procedure for specific, or a more general, application it is worthwhile to cut it off and manage it as an independent self-consistent experiment. For many of them it is also easy to find applications in other research discipline or industry. In this case it is important to verify the potentiality of the technology, customize it and improve it, in collaboration with the end user, for the specific application

Characterization of LAPPD timing at CERN PS testbeam

Large Area Picosecond PhotoDetectors (LAPPDs) are photosensors based on microchannel plate technology with about 400 cm$^2$ sensitive area. The external readout plane of a capacitively coupled LAPPD can be segmented into pads providing a spatial resolution down to 1 mm scale. The LAPPD signals have about 0.5 ns risetime followed by a slightly longer falltime and their amplitude reaches a few dozens of mV per single photoelectron. In this article, we report on the measurement of the time resolution of an LAPPD prototype in a test beam exercise at CERN PS. Most of the previous measurements of LAPPD time resolution had been performed with laser sources. In this article we report time resolution measurements obtained through the detection of Cherenkov radiation emitted by high energy hadrons. Our approach has been demonstrated capable of measuring time resolutions as fine as 25-30 ps. The available prototype had performance limitations, which prevented us from applying the optimal high voltage setting. The measured time resolution for single photoelectrons is about 80 ps r.m.s.Comment: 35 pages, 23 figure

Hybrid MPGD-based detectors of single photons for the upgrade of COMPASS RICH-1

A seven year-long R&D programme has been performed and the resulting detector architecture is a hybrid MPGD including two THick GEM (THGEM) multiplication stages followed a MICROMEGAS. The first THGEM board forms the photocathode support: its upper face is CsI coated. The properties of THGEM-based photocathodes have been studied in details. The two THGEM layers act as pre-amplification stages and, thanks to a staggered configuration, namely by the misalignment of the holes of the two THGEMs, the electron shower produced in the pre-amplification phase is distributed onto a larger surface portion of the following MICROMEGAS unit, where the final multiplication takes place: it is so possible to operate at gains as high as 105 and more even in radioactive environments. COMPASS RICH-1 is a large-size Cherenkov imaging counter with gaseous radiator for hadron identification up to 50 GeV/c. The construction of a set of large-size (unit size: 60 760 cm2) gaseous photon detectors based on the hybrid MPGD architecture for the upgrade of COMPASS RICH-1 is ongoing and the upgraded detector will be in operation in 2016. The R&D studies, the engineering aspects and the construction challenges are presented

Transverse-spin-dependent azimuthal asymmetries of pion and kaon pairs produced in muon-proton and muon-deuteron semi-inclusive deep inelastic scattering

A set of measurements of azimuthal asymmetries in the production of pairs of identified hadrons in deep-inelastic scattering of muons on transversely polarised 6LiD (deuteron) and NH3 (proton) targets is presented. All available data collected in the years 2002–2004 and 2007/2010 with the COMPASS spectrometer using a muon beam of 160 GeV=c at the CERN SPS were analysed. The asymmetries provide access to the transversity distribution functions via a fragmentation function that in principle may be independently obtained from e+e- annihilation data. Results are presented, discussed and compared to existing measurements as well as to model predictions. Asymmetries of pi+pi- pairs measured with the proton target as a function of the Bjorken scaling variable are sizeable in the range x > 0:032, indicating non-vanishing transversity distribution and di-hadron interference fragmentation functions. As already pointed out by several authors, the small asymmetries of pi+pi- measured on the 6LiD target can be interpreted as indication for a cancellation of u and d-quark transversity distributions.A set of measurements of azimuthal asymmetries in the production of pairs of identified hadrons in deep-inelastic scattering of muons on transversely polarised 6LiD (deuteron) and NH3 (proton) targets is presented. All available data collected in the years 2003–2004 and 2007/2010 with the COMPASS spectrometer using a muon beam of 160GeV/c at the CERN SPS were analysed. The asymmetries provide access to the transversity distribution functions via a fragmentation function that in principle may be independently obtained from e+e− annihilation data. Results are presented, discussed and compared to existing measurements as well as to model predictions. Asymmetries of π+π− pairs measured with the proton target as a function of the Bjorken scaling variable are sizeable in the range x>0.032, indicating non-vanishing transversity distribution and di-hadron interference fragmentation functions. As already pointed out by several authors, the small asymmetries of π+π− measured on the 6LiD target can be interpreted as indication for a cancellation of u and d-quark transversity distributions.A set of measurements of azimuthal asymmetries in the production of pairs of identified hadrons in deep-inelastic scattering of muons on transversely polarised $^6$LiD (deuteron) and NH$_3$ (proton) targets is presented. All available data collected in the years 2002-2004 and 2007/2010 with the COMPASS spectrometer using a muon beam of 160 GeV/$c$ at the CERN SPS were analysed. The asymmetries provide access to the transversity distribution functions via a fragmentation function that in principle may be independently obtained from $e^+e^-$ annihilation data. Results are presented, discussed and compared to existing measurements as well as to model predictions. Asymmetries of $\pi^{+}\pi^{-}$ pairs measured with the proton target as a function of the Bjorken scaling variable are sizeable in the range $x> 0.032$, indicating non-vanishing transversity distribution and di-hadron interference fragmentation functions. As already pointed out by several authors, the small asymmetries of $\pi^{+}\pi^{-}$ measured on the $^6$LiD target can be interpreted as indication for a cancellation of $u$ and $d$-quark transversity distributions

COMPASS Status Report 2021

The report reviews the activities and the achievements of the Collaboration during the last twelve months. Covered items are the results and ongoing analysis for the data collected in the previous years and the preparations of the 2021 run

COMPASS Status Report 2022

The report reviews the activities and the achievements of the Collaboration during the last twelve months. Covered items are the results and ongoing analysis for the data collected in the previous years and the preparations of the 2022 run

Investigation of the microstructure of Thick-GEMs with single photo-electrons

Novel Cherenkov detector upgrades favour GEM and ThickGEM based MPGD systems. These detectors have reduced ion backflow, fast signal formation, high gain, and could suppress the MIP signals as well. Their common drawbacks are the inefficiencies of photo-electron collection fromthe top of the ThickGEM and the local variation of multiplication due to the special geometry. The developed high resolution scanner using focused UV light gave the possibility to study single photo-electron response of MPGDs in the sub-millimeter scale. Revealing the microstructure of photo-efficiency and local gain provides a new tool to quantitatively compare different ThickGEM geometries and field-configurations, and thus optimize the detector parameters. The presentation will focus on the key elements of the scanning system; and on the microstructure evolution of different ThickGEM configurations