Development of Ultrafast photo-sensor instrumentation for the LHCb experiment Upgrade II for the HL-LHC regime.

After 2025 the LHC collider will enter the High Luminosity regime (HL-LHC), where the instantaneous luminosity will be enhanced an order of magnitud with respect to present 4 x 10^33 /cm^2 /s . The Upgraded (2021) LHCb detector will have to run after 2025 with the LHC beam slightly defocused (using again the lumi leverage method to get a constant lumi in LHCb) so that its detectors and DAQ system can cope with the a inelastic interaction rate per bunch crossing rate similar to that before the HL-LHC. An R&D program within the experimental heavy flavour community has started to make possible with a second LHCb Upgrade to take advantage of the full potential of the HL-LHC also in LHCb. The scheduled calendar aims to installing some prove-of-concept sub-detectors in 2025 at LHCb, in those areas that will be most affected the ageing of the current detectors. With that experience, a major refurbishing of the LHCb detector, aka LHCb Upgrade II, is foreseen in 2030 to be able to take as much data as available from the LHC and collected a total of 300/fb of pp-collision data by the end of the operation of the LHC (circa 2036). The ICCUB has started an R&D program to build a new CALO for LHCb with increased granularity (to cope with the increased multiplicity of the HL-LHC regime), increased radiation hardness and an ultrafast RO electronics capable to provide a time stamp of the data collected with a resolution below 100ps to provide time separation between the different inelastic proton-proton collisions that will take place in each LHC bunch crossing (aprox. 40). The TFM proposed will address the test of different combination of sensors (scintillating crystals), photo-sensor (SiPM, PMTs, SPADS, etc..), readout electronics (FastIC, MusIC, etc...) to consider a possible solution for an upgraded LHCb CALO for the HL-LHC..