Speaker
Description
In the high luminosity phase of the LHC (HL-LHC) the collider will operate at an instantaneous luminosity of 1.5x10$^{34}$/cm/s. This poses stringent requirements on the capabilities of subdetectors due to the increased particle multiplicity and hit occupancy. The Upgrade II LHCb RICH (Ring-imaging Cherenkov) subsystem, in particular, will require improvements in spatial and time resolution to maintain good particle identification performance in the HL-LHC environment.
To address these requirements, an improvement in the readout electronics is planned during the Long Shutdown 3 (LS3) phase, from 2026 to 2029. The goal is to provide hit timestamps with an accuracy of the order of O(100) ps from Run4 (2029-2032) onwards, in parallel with the development of novel sensors capable of sub-100 ps time resolution for Run5 (2035-2038). The LS3 enhancements foresees the use of the FastRICH, a 65-nm CMOS chip, under development by ICCUB-CERN. In my talk, a prototype opto-electronic chain with fast-timing Cherenkov photon hit detection is presented as a proof-of-principle for the future RICH detectors. This readout is equipped with the FastIC, which has a wide input signal dynamic range similar to the FastRICH.
In order to evaluate the time resolution of the prototype photo-detection chain equipped with the FastIC chip beam test campaigns were conducted in 2021 and 2022 at CERN SPS charged particle beam facility with 180 GeV/c protons and pions. The beam test setup involved a borosilicate lens placed upstream of the sensors, in order to generate Cherenkov photons and focus the Cherenkov ring on the sensor plane. The sensors used in the tests included 1-inch and 2-inch Multi-Anode Photomultipliers currently used in the LHCb RICH, as well as a Silicon Photomultiplier matrix. Each sensor was accompanied by a dedicated front-end board and a digital board (DB) for signal extraction. The DB incorporated a custom Time-to-Digital Converter implemented in an FPGA with an average bin width of 150 ps. The trigger for the setup was provided by a crossed pair of scintillators combined with a Micro-Channel Plate Photomultiplier, which served as the time reference for the system.
To assess the time resolution of the prototype, specific time reconstruction algorithms were developed. The results show that the estimated Single Photon Time Resolution of the 1-inch and 2-inch MaPMTs, considering all sources of jitter, is compatible with the expected MaPMT transit-time-spread of approximately 150 ps. Additionally, the measurements obtained from the beam test were validated through dedicated laser measurements conducted in the laboratory.
To further validate the beam test conditions and their effects on time resolution, a comprehensive GEANT4 simulation was performed. This allowed for a detailed study of the beam effects on the time resolution and a comparison between the expected and observed photon yields.
In this talk the setup for a prototype photodetector module for future fast-timing RICH detectors is presented, with a focus on the final results coming from the timing analysis and on the corrections applied to account for the time-walk effect.
| Collaboration / Activity | LHCb |
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