Gamma-Ray- and Neutron-Induced Photocurrent and Readout Noise in LYSO+SiPM Packages
Lu_(2(1–x))Y_(2x)SiO₅ (LYSO) crystals readout by a silicon photomultiplier (SiPM) will be used in the barrel timing layer of a precision timing detector for the Compact Muon Solenoid (CMS) experiment at the High-Luminosity Large Hadron Collider (HL-LHC). This detector is expected to be exposed up to 5-Mrad γ-ray dose, 2.5×10¹³ charged hadrons/cm², and 3×10¹⁴n_(eq)/cm² at the HL-LHC for 10 years of operation. We present results of the photocurrent in LYSO+SiPM packages induced by Co-60 γ-rays and Cf-252 neutrons of the expected dose rate and neutron flux, respectively. The γ-ray-induced readout noise is about 30 keV, which is negligible when compared to the 4.2-MeV signal from the minimum ionization particle signals. The neutron-induced readout noise is about 7 keV, which is more than a factor of 4 smaller than that from the γ-rays.