Performance of the ALICE HMPID detector during the LHC run period 2010$-$2015 and perspectives

In this note the performance of the ALICE High Momentum Particle IDentification (HMPID) detector during the LHC run period 2010$-$2015 is presented. The HMPID extends the charged hadron identification capability of the ALICE apparatus at high momenta, identifying with three sigma separation power charged pions and kaons in the momentum range 1$-$3 GeV/$c$ and (anti-)protons in the range 1.5$-$5 GeV/$c$. It consists of seven Ring Imaging Cherenkov (RICH) modules, 1.3$\times$1.32$\times$0.3 m$^3$ each. The detection of Cherenkov UV photons is achieved by Multiwire Proportional Chambers (MWPCs) with CsI pad segmented photocathodes, for a total active area of 10.3 m$^2$. The Cherenkov radiator used is the liquid C$_6$F$_{14}$ (perfluorohexane) with $n$ = 1.299 at a photon wavelength $\lambda$ = 175 nm. The detector stability with emphasis on the CsI quantum efficiency and the Particle IDentification (PID) performance, by means of both statistical and track-by-track approaches, are presented. Finally, the perspective of the detector operation during the Run 3 data-taking period (2022$-$2024) with Pb$-$Pb runs at 50 kHz of collision rate, is briefly discussed and evidence for the effective detector operation is provided.