A computational study of the response of Ge and NaI(Tl) detectors to the inner bremstrahlung of 90Y

The convoluting effects of detector response on a continous photon spectrum was studied in a 30% Ge detector and three NaI(Tl) spectrometers using detailed Monte Carlo calculations. The diameters and length of the cylindrical scintillation crystals were:5.08 × 5.08 cm², 7.62 cm², and 12.7 × 12.7 cm². The internal bremsstrahlung spectrum of ⁹⁰Y was calculated using the theory of Ford and Martin which include nuclear diagrams. It is clearly shown that recent experimental results, which deviate seriously from theory, are not explained by detector response. A direct comparison to the method of Lidén and Starfelt is made in a typical case. The calculations suggest aan experimental geometry which minimizes the distortion due to photons scattering out of the detector.