Performance of large volume CsI(Tl) scintillators coupled to silicon photodiodes in gamma-ray spectroscopy

For many years researchers have tried to replace the photomultiplier tube by a solid state photodiode in scintillation probes. Silicon avalanche diodes have first been investigated, but high sensitivity to any temperature changes limited their use. Conventional silicon-based photodiodes are manufactured by using high resistivity silicon and planar technology, and have opened new possibilities involving the use of compact scintillation probes operating at very low bias with current densities in the order of 1 nA/cm2. Gamma ray spectrometers have recently been built that couple 1 cm2 silicon photodiodes to small scintillators. We discuss the possibility of using similar photodiodes in conjunction with much larger scintillators (up to 2 in. in diameter and 2 in. in height) in gamma-ray spectroscopy. Their superior performance is discussed, along with the effects of electronic noise, gamma-ray energy and mode of coupling.