Ionization Dose and Neutron Induced Photocurrent and Readout Noise in LYSO+SiPM Packages

The barrel timing layer for the CMS HL-LHC precision timing detector will be constructed using LYSO+SiPM modules. The barrel in HL-LHC beam intensities is expected to be exposed under an ionization dose rate of up to 200 rad/h and a neutron flux of up to 3×10
⁶
neq/cm
²
/s. We present results from measurements of photocurrent in the LYSO+SiPM packages induced by Co-60 γ-rays and Cf-252 neutrons. The γ-ray induced readout noise is found to be about 30 keV, which is negligible compared to the 4.2 MeV signal from minimum ionization particles. The neutron induced noise is about 7 keV, which is more than a factor of 4 smaller than that from the ionization dose.