Single photoelectron time resolution studies of the PICOSEC-Micromegas detector

Detectors with a time resolution of a few tens of picoseconds and long-term durability in high particle fluxes are necessary for an accurate vertex separation in future particle physics experiments. The PICOSEC-Micromegas detector concept is a Micro-Pattern Gaseous Detector (MPGD) based solution addressing this particular challenge. It is based on a Micromegas detector coupled to a Cherenkov radiator and a photocathode. Primary electrons from the incident particles are generated in the photocathode and the time fluctuations due to different primary ionisation positions in the gaseous volume are reduced. The feasibility to reach a good time resolution using this concept was demonstrated in test beam studies, and time resolution values down to 24 ps were measured with muon beams at the CERN SPS accelerator complex. The previously simulated effects of different detector parameters on the time resolution were confirmed by measurements. For these measurements, a femtosecond laser system is used. For a single photoelectron, a time resolution of better than 50 ps is achieved mostly by minimising the drift gap distance. Furthermore, gain and Amplitude-to-Signal ratio (A/Q) with different gas mixtures are compared.