Speaker
Description
Recent advances in timing detectors at CERN have largely focused on mitigating pileup background in the HL-LHC era. The CMS and ATLAS upgrades addressed the challenges arising from track density and radiation dose- particularly in the forward region. Over the same period generic timing R&D based in the Silicon detector and MicroPattern Gas detector(MPGD) groups developed technologies more suited to the FCC-ee barrel timing where 20-30 picosecond resolution was achieved with coarser (~ 1cm^2 pixel area) sensor elements. We report on the earlier High Gain Avalanche diodes and PICOSEC.
The MPGD project- PICOSEC- has achieved a 2 order of magnitude improvement in timing (ie 20 picosec compared to 1-2 nsec) state of the art for Micromegas(MM). It is based on a Cherenkov radiator coupled with a semi-transparent photocathode and a MM amplifying structure, targeting a time resolution of tens of picoseconds for minimum ionizing particles. The first single-pad prototypes demonstrated a time resolution below sigma= 25 ps and several developments are being pursued to make the concept suitable for physics applications.
The objective is to build robust multichannel detector modules for large-area systems requiring good time resolution. Intense R&D activities within PICOSEC have covered all areas from simulations, design, production and assembly as well as measurements in the lab and with 150 GeV/c muon beams.
One of the project’s milestones was scaling up the prototype to a 100-channel detector with an active area of 10x10 cm2. A time resolution below sigma = 18 ps for individual pads was demonstrated. Regarding robustness, a 10x10 cm2 area resistive PICOSEC MM of 20 MΩ/□ was produced and a time resolution of 20 ps for individual pads was obtained. Furthermore, detailed measurements of carbon-based photocathode samples, including Diamond Like Carbon (DLC) and Boron Carbide (B4C) are ongoing to find an alternative to Cesium Iodide. Preliminary results from single- and multi-channel detectors equipped with DLC and B4C photocathodes showed a time resolution below 35 ps.
