Large volume CdWO4 crystal scintillators

A low background scintillation spectrometer based on CdWO4 crystals of large volume (100-200 cm(3)) with improved energy resolution has been developed as a result of advances in crystal growth, optimization of light collection and design of a special electronic unit for amplification and shaping of the CdWO4 signals. The energy resolution of crystals with volume 80-150 cm(3) is 10-12% for 662 keV gamma-rays. A value of 7-8% at 662 keV, which is comparable to NaI(TI), has been obtained with small samples (10-20 cm(3)). The high purity of the CdWO4 crystals (Th-228 contamination is less than 8 mu Bq/kg, that of Ra-226 less than 13 mu Bq/kg) allows construction of unique spectrometers based on CdWO4 crystals of large volume for environmental control, well logging and measurements of radioactive contamination in various samples with a sensitivity of 10(-12) to 2 x 10(-13) Ci/kg.