Development and Evaluation of a Miniature Scintillation Gamma Spectrometer for Environmental Radiation Monitoring

Developing a compact gamma spectrometer for radiation monitoring in critical zones, such as nuclear power plants and the Chernobyl Exclusion Zone, is vital for ensuring high sensitivity and accurate measurements amid geopolitical instability and military aggression. The aim of the study was to demonstrate the feasibility of a miniature scintillation spectrometer using a lutetium-yttrium oxyorthosilicate crystal (LYSO) and a silicon photomultiplier (SiPM) or multi-pixel photon counter (MPPC), and to compare it with an existing compact photomultiplier tube (PMT) R7400U assembly with a thallium-doped caesium iodide crystal (CsI(Tl)). The first stage involved preparing a prototype board for the R7400U PMT and analyzing its spectrometric characteristics. Next, an experimental setup using the LYSO crystal, SiPM photodiode, preamplifier electronics, and a spectrum analyzer was assembled, while gamma radiation interaction was modeled with GEANT4. Experimental measurements with a Cesium-137 (137Cs) source (661.7 keV) showed that the spectrometer could register and analyse gamma spectra with moderate resolution. The SiPM signal remained stable with optimal electronics and a 400 V DC-DC converter, providing low noise. Experimental data matched Monte Carlo simulations, and the SiPM's large pixel count ensured better response linearity at high light intensity. As a result, the design proved stable and effective for long-term measurements. The proposed approach demonstrated the possibility of such miniaturisation of spectrometric systems without significant degradation of performance. The study demonstrated the feasibility of a miniature scintillation spectrometer with LYSO and SiPM/MPPC, performing similarly to the PMT-based system. This compact design offers a viable solution for portable radiation monitoring in critical environments.