Photodetectors and front-end electronics for the LHCb RICH upgrade

TL;DR

This paper details the development and testing of new photodetectors and front-end electronics for the LHCb RICH upgrade, enabling higher rate data collection and improved particle identification in high-energy physics experiments.

Contribution

It introduces a new 8-channel front-end chip, CLARO, and upgraded MaPMT photon detectors, enhancing performance, stability, and radiation hardness for the LHCb RICH detector upgrade.

Findings

MaPMTs meet experimental requirements with high gain and low dark count

CLARO chip achieves low power, high bandwidth, and radiation hardness

Performance and stability of detectors and electronics are validated

Abstract

The RICH detectors of the LHCb experiment provide identification of hadrons produced in high energy proton-proton collisions in the LHC at CERN over a wide momentum range (2 to 100 GeV/c). Cherenkov light is collected on photon detector planes sensitive to single photons. The RICH will be upgraded (in 2019) to read out every bunch crossing, at a rate of 40 MHz. The current hybrid photon detectors (HPD) will be replaced with multi-anode photomultiplier tubes (customisations of the Hamamatsu R11265 and the H12699 MaPMTs). These 8$\times$8 pixel devices meet the experimental requirements thanks to their small pixel size, high gain, negligible dark count rate ($\sim$50 Hz/cm$^2$) and moderate cross-talk. The measured performance of several tubes is reported, together with their long-term stability. A new 8-channel front-end chip, named CLARO, has been designed in 0.35 $\mu$m CMOS AMS technology for the MaPMT readout. The CLARO chip operates in binary mode and combines low power consumption (\hbox{$\sim$1 mW/Ch}), wide bandwidth (baseline restored in $\leq$25 ns) and radiation hardness. A 12-bit digital register permits the optimisation of the dynamic range and the threshold level for each channel and provides tools for the on-site calibration. The design choices and the characterization of the electronics are presented.