Towards robust PICOSEC Micromegas precise timing detectors

International audience; 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 non-resistive PICOSEC MM prototype with 10x10 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 10x10 cm$^2$ area resistive PICOSEC MM of 20 M$\Omega$/sq 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 (B$_4$C) 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.