The aim of the LHCb Upgrade II is to operate at a luminosity of 1.0 x 1034 cm-2s-1 to collect a dataset of 300 fb-1. This requires a substantial modification of the current Electromagnetic Calorimeter (ECAL) during LS4, due to the increased particle rate and the resulting radiation doses in the central region. An enhancement already during LS3 will reduce the occupancy in the central region and mitigate significant ageing effects after Run 3.

During LS3, the inner regions, closer to the beampipe, will be equipped with new modules based on Spaghetti Calorimeter (SpaCal) technology, comprising lead or tungsten absorbers and plastic radiation-tolerant scintillating fibres. The present Shashlik modules in the outer regions will be re-arranged. After LS4, a new ECAL configuration (called PicoCal) will feature increased granularity, radiation hardness, and introduce picosecond timing. New SpaCal modules will be produced and inorganic crystal fibres will be employed in the highest radiation region. The Shashlik modules will be refurbished with faster wavelength-shifting fibres and photodetectors, to improve timing.

The R&D led to multiple full-size modules designed, assembled, and successfully tested. The energy resolution features sampling and constant terms in line with the targets of 10% and 1%, respectively. The time resolution is better than 20 ps for all prototypes with electrons of tens of GeV. The results are well described by detailed Monte Carlo simulations.

 The presentation will give an overview of the LS3 Enhancement and the PicoCal project, before detailing the R&D performed and the ongoing optimisation, from the production of the absorbers and the development of innovative fast and radiation-hard scintillators, to the design of the readout electronics for picosecond timing.

Coffee will be served at 10:30