The upgrade of the LHCb RICH system for the LHC Run 3

The RICH detectors of the LHCb experiment have provided particle identification with excellent performance during Runs 1 and 2 of the LHC . Currently the LHCb experiment is undergoing an upgrade to allow, starting from 2021, data collection at 5 times the instantaneous luminosity of the period 2010-2019 (up to 2 × 10$^{33}$cm$^{-2}$ s $^{-2}$ ) with the aim to collect a data sample corresponding to 50 fb$^{-1}$. The required upgrades to detectors and electronics are significant, with the RICH system changing all of the photon detectors and a full replacement of the upstream RICH detector. The existing Hybrid Photon Detectors (HPD) are being replaced by two types of Multi-Anode Photomultiplier Tubes (MaPMT) with electronics capable of recording data at the full LHC collision frequency of 40 MHz using a time gate of 6 ns. The required 3072 MaPMTs have undergone detailed characterisation, measuring gain and uniformity across channels and the photo-cathode quantum efficiency on a smaller sample. The status of the project will be presented.