Abstract: The ptype coaxial highpurity germanium detector was used to measure the decay γ energy spectrum of ^226Ra which came from fluorescent instrument panel and ¹³³Ba standard source, the energy and intensity of characteristic γrays were analyzed. The results show that the characteristic rays of ^226Ra and a large number of characteristic γ rays of the decay daughter nucleus of ²²⁶Ra appear in the ²²⁶Ra spectrum. There are large number of sum peaks in ¹³³Ba γ spectrum except its own characteristic rays. The existence of sum peaks is proved from the relationship between counting rate and distance and γ ray cascade.

Key words: characteristic ray, decay &gamma, counting rate, sum peak, energy spectrum