Abstract: A practical method for measurement of cascade gamma radiation nuclide by HPGe gamma spectrometer is given. A certain thickness water absorption layer is placed between the detector and the sample, which can reduce the detection efficiency and reduce the effect of the cascade gamma coincidence effect. Experiments showed that the detection efficiency and activity relative deviation of ¹³³Ba, ⁶⁰Co and ¹⁵²Eu radionuclide in TC-45 samples are followed by exponential decay with the increase of the water absorption layer thickness. When the thickness is increased to 70 mm, the relative deviation of measurement is less than 4%.

Key words: absorbing layer, coincidence, gamma cascade