INFLUENCE OF RADIATION-DAMAGE ON BGO SCINTILLATION PROPERTIES

Aboard INTEGRAL, the nest medium-size gamma-ray mission of the Europea n Space Agency (ESA), a high-resolution Ge-spectrometer array with a B GO anticoincidence shield and imaging capability will be flown. The in fluence of the radiation damage on the photoelectron yield of the BGO scintillators due to the radiation environment in the orbit, i.e. gamm a-rays, electrons and protons from the radiation, belts and the cosmic diffuse radiation. was investigated. Irradiation tests with doses equ ivalent to the orbit conditions were performed and the photoelectron y ields of different BGO crystals were measured. It was found that for e qual doses the reduction of the photoelectron yield varies strongly fo r the crystals of different manufacturers. Furthermore. electromagneti c radiation affects the photoelectron yield much stronger than particl e radiation. A possible explanation is given by interpreting the effec t due to gamma-rays primarily as damage of the electronic structure of the BGO, whereas the particle radiation damages mainly the crystal st ructure. (C) 1998 Elsevier Science B.V. All rights reserved.