Experimental Determination of Detector-Relevant Properties of ZnSe(Al,O) for Beta Spectroscopy.

ZnSe-based scintillators are promising materials for compact beta spectroscopy, but the detector-relevant properties of ZnSe(Al,O) remain poorly documented and strongly dependent on dopant and defect structure. This work presents an experimental characterisation of a commercially supplied ZnSe(Al,O) crystal intended for an SiPM-based beta detector to Sr-90/Y-90 detection. A scanning electron microscope with energy dispersive x-ray spectroscopy (SEM-EDS) was used to verify the elemental composition and examine surface artefacts, while optical and scintillation properties were determined through density measurement, Brewster-angle refractive index measurement, UV-excited emission spectroscopy, Sr-90/Y-90 charge-spectrum analysis, and waveform decay fitting. The crystal was found to contain Zn, Se, Al, and O, with average atomic abundances of 50.3%, 44.0%, 1.2%, and 4.5%, respectively. The measured density was 5.31 g cm-3 and the refractive index was 2.574 at 650 nm. The emission spectrum peaked at approximately 581 nm, within the visible response range of silicon photodetectors. Sr-90/Y-90 beta measurements gave an estimated intrinsic light yield of approximately 7.69×104 photons MeV-1, while exponential fitting of digitised waveforms gave a decay time of 9.41 μs. These results provide an experimentally determined parameter set for this ZnSe(Al,O) crystal and support its use in compact beta spectroscopy, while also highlighting the need for direct material characterisation before reliable detector simulation.