g-Ray Summing in Germanium Detectors and Its Effects on Nuclear Decay Parameters

Abstract

The random, genuine and coincidence summing due to photons in germanium detectors are studied as a function of source detector distances. The radioactive isotope of 133Ba has been used for the purpose of genuine sum peaks. The source to detector distances kept at 2.5, 5.0 and 10.0 cm have revealed the exponential fall in sum peak areas. A typical random sum-peak at 867 keV due to 356 keV and 511 keV photo peaks from ¹³³Ba and ²²Na has been observed. The random summing has been found to increase with increase in the energies of the photo peaks being added. This phenomenon is about 2.4 % of the genuine (356 + 81) keV sum peak. The 81 keV photons having intensity as high as 34.2 ± 1.9 units/100 decays of the parent nucleus could not show any summing with 511 keV peak. The resolving time of the detector found to depend strongly on count rate is determined as 1.8 ± 0.1 micro-seconds.