Sneha Malde

Abstract:

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.

Abstract:

Particle Identification is a key requirement for future Higgs factories such as FCC-ee at Future Circular Collider. The ARC (Array of RICH Cells) detector is a compact and modular Ring Imaging Cherenkov (RICH) concept designed for π/K separation in the 1–40 GeV/c momentum range. It combines gas and aerogel radiators in independent cells equipped with mirrors and SiPM-based photon detectors. Simulation studies, including inverse ray-tracing reconstruction, confirm the expected photon yield and PID performance. A key challenge for SiPM-based RICH systems is noise reduction. We present the development of a compact and scalable SiPM housing module integrating mechanical support, front-end compatibility, and active cooling. The design builds on the Elementary Cell concept of the LHCb RICH Upgrade and extends it with embedded thermal management at sensor level. Thermal modelling and prototype measurements demonstrate stable and uniform operation at temperatures down to -80°C. This approach provides a viable solution for low-noise SiPM modules for next-generation RICH detectors.

Abstract:

The TORCH time-of-flight detector is part of a proposed upgrade of the LHCb experiment, foreseen for the high-luminosity phase of the LHC. The TORCH detector provides particle identification of hadrons in the sub-10 GeV/c momentum range, exploiting the prompt production of Cherenkov photons in an array of fused-silica plates. Photons are propagated to the periphery of the detector via total internal reflection, where they are focused by a cylindrical mirror onto an array of fast-timing MCP-PMT photon detectors. In order to achieve the design goals of TORCH, individual photons must be timed to 70ps precision or better. The development of the MCP-PMTs, the mechanical design and assembly strategy of a full-scale TORCH detector module, plus its system-level validation in a test beam are described. A validation of timing references, the optical integrity across glue joints and the readout integration are presented.

Abstract:

Particle Identification (PID) is a key requirement for future Higgs factories such as FCC-ee, in particular for heavy-flavour physics and jet flavour tagging. The ARC (Array of RICH Cells) detector is a novel compact and modular RICH (Ring Imaging Cherenkov) concept designed to provide charged hadron separation over a momentum range 1 − 40 GeV/c . ARC combines gas and aerogel radiators within independent cells, each equipped with spherical mirrors and SiPM-based photodetectors. A detailed simulation and reconstruction framework has been developed, including inverse ray-tracing algorithms for Cherenkov angle reconstruction. Simulation studies demonstrate excellent photon yield and π / K separation performance across the target momentum range.

Abstract:

We present a Monte Carlo-based simulation stack that provides time-of-flight (ToF)-resolved blood flow index (BFi) and has been validated against continuous-wave (CW) and time-resolved BFi measurements in both tissue-mimicking phantoms and in-vivo. Using this simulation, we evaluated the influence of key parameters including source-detector separation, ToF selection, and minimum resolvable lag on brain sensitivity by comparing simulated pulsatile blood flow signals from scalp and brain layers. We used these results to optimise the design of CoMind Research One (R1), a 16-channel interferometric time-of-flight-resolved optical neuromonitoring system that operates in real time and enables high-fidelity measurements of field autocorrelation at times-of-flight exceeding 1 ns. We validated this system and demonstrated its depth sensitivity using homogeneous and bi-layer dynamic tissue-mimicking phantoms. The advancements in optical throughput, depth selectivity, and robustness demonstrated by CoMind R1 pave the way for clinical translation and broader adoption of non-invasive optical measurements of cerebral blood flow.