SiPM optical readout of a PICOSEC Micromegas precise timing detector

Abstract

By combining a Cherenkov radiator with a semi-transparent photocathode and a two-stage Micromegas amplification element, PICOSEC Micromegas detectors have achieved <20 ps charged-particle time resolution with electronic readout of induced signals. Building upon this performance, we describe SiPM-based optical readout as a novel technique for PICOSEC Micromegas detectors. Single-channel detector prototypes based on glass Micromegas technology were read out with an array of SiPMs. To allow operation in a strongly quenched gas mixture, a solid wavelength shifter is integrated in the glass Micromegas to convert UV scintillation to the visible range and maximise scintillation light output. Timing performance of glass Micromegas in electronic and optical readout modes is compared and <150 ps time resolution is achieved by optically read out scintillation light signals. The achievable spatial resolution from centre-of-gravity reconstruction of event positions from the amplitudes of signals on multiple SiPM channels is σ = 1.25 mm. This demonstrates the possibility of dual-readout of PICOSEC glass Micromegas: electronic signals and optical signals. Finally, camera-based optical readout is presented to demonstrate imaging as another avenue for position reconstruction.