Simulation and characterisation of a 16-by-96 multi-anode MCP-PMT for the TORCH detector

Owing to their single-photon sensitivity and fast rise time, micro-channel-plate photomultipliers (MCP-PMTs) make good candidates as photon detectors for the Time Of Internally Reflected CHerenkov light detector (TORCH) that is proposed as part of the phase two upgrade of the LHCb experiment. The TORCH detector has a target time resolution per photon of approximately 70 ps, required to achieve an approximately three standard deviation separation of pions and kaons at 10 GeV/ c from their time-of-flight over a 10 m flight distance. A new high-granularity 16-by-96 channel MCP-PMT with a directly coupled anode has been developed in conjunction with Photek Ltd. This device is designed to decrease the pixel pitch to 0.55 mm in the fine pixel direction, giving improved spatial resolution and importantly lower per-pixel occupancies. This paper will cover cross-talk characterisation studies, used to determine the spatial resolution of the device. The experimental results are compared with simulation studies. Overall, the results demonstrate minimal effects of cross-talk on the device's output. A study of a TORCH demonstrator, using older 8-by-64 channel MCP-PMTs, has also been carried out in a beam test at CERN. Initial results from the demonstrator show suitable mechanical and optical performances.