Application of a SrI2(Eu) scintillation detector to in situ gamma-ray spectrometry in the environment

Highlights: • A SrI₂(Eu) detector was applied to the in situ gamma-ray spectrometry in the environment. • The optimized pulse shaping time of 12 μs was determined from the performance test. • The dose conversion factor was calculated to make a spectrometric determination of dose rate. • The experimental verification was conducted by comparing results from NaI(Tl) and HPGe detectors. -- Abstract: Using scintillation detectors to spectrometrically determine dose rate is useful in response to a nuclear accident, because the nuclide contribution in the measured dose rate can be determined. However, to select an appropriate scintillator for in situ gamma-ray spectrometry in the environment, energy resolution and counting efficiency should be evaluated. A SrI₂(Eu) crystal is one of the promising scintillators, with good energy resolution and light output performance. But its long scintillation decay time of about 1 μs needs to be well matched with the signal processing unit of the gamma-ray spectrometer to avoid degrading its good performance. In this study a performance test was first conducted to determine the optimized pulse shaping time in the gamma-ray detection process. In addition, a Monte Carlo simulation of the SrI₂(Eu) detector was performed to establish the algorithm for the spectrometric determination of dose rate. Finally, in situ gamma-ray spectrometry was performed with the SrI₂(Eu) detector to determine the ambient dose rate, as well as the dose rate of nuclides in the environment. The results were successfully compared with those of HPIC (high pressure ion chamber), portable HPGe (high purity Ge), and NaI(Tl) detectors at the same site.