Optimized Bi4Si3O12 scintillation crystals grown in dynamic atmosphere for future particle physics experiments

This work deals with the optimization of bismuth silicate, Bi4Si3O12 (BSO) scintillation crystals as candidates for future high energy physics experiments at colliders involving the registration of both scintillation and Cherenkov light. Crystals with a high transparency in UV-band and a high timing resolution are required for this application. Czochralski process was employed for BSO crystal growth in Pt crucibles in a dynamic growth atmosphere. After the growth of a series of crystals in air, as well as mixed Ar-air static and dynamic atmospheres, it was shown that the mixed atmosphere minimizes Bi2O3 evaporation and reduces the amount of Pt dissolved in the melt by several times. This caused the reduction in the number of foreign inclusions in the grown crystals, providing a transparency of over 70 % in the > 300 nm range, a light output of up to 2140 ph/MeV, an energy resolution of 21.5 % at 662 keV gamma-rays, while a coincidence time resolution was improved from 148 to 125 ps.