RICH1 for the LHCb experiment

The two ring-imaging Cherenkov (RICH) detectors, RICH1 and RICH2, located upstream and downstream of the LHCb magnet 1 and 10 m away from the collision point, provide excellent particle identification over a wide momentum range. Both have been refurbished to cope with the more challenging data-taking conditions of Run 3. The photon detection system has been redesigned. Two types of 64-channel multi-anode photomultiplier tubes have been selected to detect single photons, while providing excellent spatial resolution and low background noise. The optical system of the RICH1 detector has all been upgraded. To reduce the number of photons in the hottest region, its optics have been redesigned to spread the Cherenkov rings over a larger surface.