Survey of the properties of BGO crystals for the Extreme Forward Calorimeter at BELLE

We check the scintillation light yield of all EGO crystals used for the Ext reme Forward Calorimeter (EFC) at BELLE. The percentage spread of the distr ibution is only 6%. The nonuniformity of the light yields measured lengthwi se for the forward EFC is close to 13% and is similar to 0% for the backwar d EFC. The test crystals, two per ingot, from mass-production are subjected to the radiation hardness test. The results obtained at BINP and NTU are i n good agreement. Some EFC crystals, selected randomly, show the light yiel ds drop about 25-50% after receiving 1 krad dose and remain stable afterwar ds. There is little sensitivity to the rate that the 1 krad dose is receive d, since the recovery process is very slow, in the order of days to weeks. (C) 2000 Elsevier Science B.V. All rights reserved.