Performance and upgrade plans of the ALICE Photon Spectrometer

PHOS is a highly granulated precision spectrometer, one of the two electromagnetic calorimeters of ALICE (A Large Ion Collider Experiment) at the LHC. It is based on scintillating PbWO4 crystals and is dedicated to the precise measurements of spectra, correlations and collective flow of neutral mesons, thermal and prompt direct photons in ultra-relativistic nuclear collisions at LHC energies. PHOS participated in LHC Run 1 (2009–2013) and Run 2 (2015–2018), during which a large amount of physical data were collected in pp, p-Pb and Pb-Pb collisions.We present an overview of the PHOS performance during Runs 1 and 2 and plans for an upgrade for future LHC runs.