CALIFA is the high efficiency and energy resolution calorimeter for the R3B experiment at FAIR, intended for detecting high energy light charged particles and gamma rays in scattering experiments, and is being commissioned during the Phase-0 experiments at FAIR, between 2018 and 2020. It surrounds the reaction target in a segmented configuration with 2432 detection units made of long CsI(Tl) finger-shaped scintillator crystals. CALIFA has a 10 year intended operational lifetime as the R3B calorimeter, necessitating measures to be taken to ensure enduring performance. In this paper we present a systematic study of two groups of 6 different detection units of the CALIFA detector after more than four years of operation. The energy resolution and light output yield are evaluated under different conditions. Tests cover the aging of the first detector units assembled and investigates recovery procedures for degraded detection units. A possible reason for the observed degradation is given, pointing to the crystal-APD coupling.
@article{arxiv.2003.01485,
title = {Performance recovery of long CsI(Tl) scintillator crystals with APD-based readout},
author = {P. Cabanelas and D. González and H. Alvarez-Pol and J. M. Boillos and E. Casarejos and J. Cederkall and D. Cortina and M. Feijoo and D. Galaviz and E. Galiana and R. Gernhäuser and P. Golubev and A. -L. Hartig and P. Klenze and A. Knyazev and T. Kröll and E. Nácher and J. Park and A. Perea and B. Pietras and L. Ponnath and H. -B. Rhee and J. L. Rodríguez-Sánchez and C. Suerder and O. Tengblad and P. Teubig},
journal= {arXiv preprint arXiv:2003.01485},
year = {2020}
}