Readout of plastic scintillators with cooled large-area avalanche photodiodes

Time-of-flight measurements in multifragmentation of heavy, relativistic projectiles require very good time resolution and at the same time the detecting system must cope with a dynamic range of up to 8000:1. We look into the possibility of application of large-area avalanche photodiodes (LAAPDs) as alternative light sensors to meet the above requirements. The paper presents the results of our amplitude and time response studies of a plastic scintillator BC-408 readout with a φ16 mm LAAPD using radioactive sources. The measurements were performed using two different setups. The best time resolution has been obtained by exploiting LAAPD cooling to increase its gain beyond that accessible at room temperature. We reach 610 ps (FWHM) at −26°C for the corresponding LAAPD gain of ≈900 and the 90Sr/90Y β-ray source. We hope to reach below the desired 400 ps with the latter setup at the higher light levels available with multifragmentation products.