GAMMA-RAY DETECTION WITH AN UV-ENHANCED PHOTODIODE AND SCINTILLATION CRYSTALS EMITTING AT SHORT WAVELENGTHS

A low-noise ion implanted photodiode with high spectral response in th e deep blue/UV region has been tested as read-out device for scintilla tion crystals with matching emission spectra (YAP(Ce), GSO(Ce), BGO an d CsI(TI)). This gamma-ray detector concept is attractive in many indu strial applications where compactness, reliability and ambient tempera ture operation are important. The results show that the amount of dete cted scintillation light energy falls rapidly off as the wavelength of the scintillation light decreases. It is concluded that the dynamic s pectral response of the photodiode, due to increasing carrier collecti on times, is considerably less than the DC response at short wavelengt hs. The diode is not useful in pulse mode operation with scintillation crystals emitting at wavelengths below about 400 nm. For read-out of CsI(Tl) with 661.6 keV gamma-radiation, however, the photodiode concep t shows better energy resolution (7.1%) than other detectors.