Development of <italic>In Situ</italic> Selective Beta-Ray Distribution Detection Technology Based on Gamma-Ray Sensitivity Difference

An in situ detection method for beta-ray distribution was developed. The method uses the gamma-ray sensitivity difference between two scintillators: a cadmium-tungstate (CdWO ₄ ) scintillator and a plastic scintillator. The gamma-ray sensitivity ratios for several gamma-ray sources such as ¹³⁷ Cs, ⁶⁰ Co, ²² Na, and ⁵⁴ Mn were experimentally characterized. The sensitivity ratio for ¹³⁷ Cs between the CdWO ₄ and plastic scintillators was 8 ± 0.32, while the sensitivity ratio for beta rays from ⁹⁰ Sr was 1.03 ± 0.006. The beta-ray contributions to the total counts can be evaluated using this characteristic. A combined beta-ray and gamma-ray source was prepared, and its beta-ray distribution was successfully obtained using the proposed method.