Towards robust picosec micromegas precise timing detectors

Abstract

The PICOSEC Micromegas (MM) detector is a precise timing gaseous detector consisting of a Cherenkov radiator combined with a photocathode and a MM amplifying structure. A 100 channel PICOSEC MM prototype with 10 x 10 cm(2) active area equipped with a Cesium Iodide (CsI) photocathode demonstrated a time resolution below sigma = 18 ps. The objective of this work is to improve the PICOSEC MM detector robustness aspects, i.e. integration of resistive MM and carbon-based photocathodes, while maintaining good time resolution. The PICOSEC MM prototypes have been tested in laboratory conditions and successfully characterised with 150 GeV/c muon beams at the CERN SPS H4 beam line. The excellent timing performance below sigma = 20 ps for an individual pad obtained with the 10 x 10 cm(2) area resistive PICOSEC MM of 20 M Omega/square showed no significant time resolution degradation as a result of adding a resistive layer. A single-pad prototype equipped with a 12 nm thick Boron Carbide (B4C) photocathode presented a time resolution below sigma = 35 ps, opening up new possibilities for detectors with robust photocathodes. The results made the concept more suitable for the experiments in need of robust detectors with good time resolution.