Study of a prototype module of a precision time-of-flight detector for particle identification at low momentum

In this thesis, Time Of internally Reflected Cherenkov light detector (TORCH), proposed for the LHCb Upgrade to perform three-sigma separation between kaon and pion up to 10 GeV/c, was studied. TORCH is designed to add significant particle identification capability to the existing LHCb system based on two gas Ring Imaging Cherenkov detectors. TORCH would be placed at  10 m from the interaction point, where the flight time difference between a primary pion and kaon is 37.5 ps. TORCH will give a pion-kaon separation of three sigma at 10 GeV/c from the flight time using the Cherenkov photons generated by the charged particle in a 1 cm-thick quartz plate. In order to calculate accurately the flight time in a busy LHCb environment, Cherenkov angle and photon detection time information, as well as the momentum information from the tracking detector are included in the analysis. For the required TORCH performance, the flight time difference must be measured with a resolution of better than 70 ps for a single Cherenkov photon. In order to demonstrate the required performance, the intrinsic time resolution of the photon detector and electronics jitter have been investigated, firstly with commercially available Micro-Channel Plate Photo Multiplier Tubes (MCP-PMT) and electronics, then custom-made Multi-Channel MCP-PMT with custom-made electronics, which are designed for the TORCH R&D.; The Multi-Channel MCP-PMT has been developed in collaboration with industry. For the custom electronics, NINO, an ASIC chip developed for the Time of Flight detector of the ALICE experiment was used as well as the HPTDC ASIC chip, which is being used by the ATLAS, CMS and ALICE experiments. Important characteristics such as the linearity and time walk have been carefully analysed and a method to correct biases introduced by those characteristics has been developed. TORCH optics must propagate the Cherenkov photons to the photocathode of the Multichannel MCPMT with minimum loss. On the other hand, spectra of photons reaching the photocathode should not be too wide in order to limit the chromatic error. All the optical components have been tested with a stand-alone system and results are compared with simulation studies. A small scale TORCH prototype has been constructed to test the system with a charged-particle beam and results are being analysed.

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