total and photo peak relative efficiency measurement for NaI[T1] detector

In the present work, total and photo peak relative efficiency were measured for NaI[T1]. Two radioactive sources [Co-60 and Cs- 137] with detector NaI[T1] by size [3 " x 3 "] were used. The range of angles [10 °-90 °] and the range of distance between the sources and crystal [10-30] cm. The experimental results show: When increasing the angle the photo peak relative efficiency increasing. And increasing it's the total relative efficiency increase until [50 °] after these angle the total efficiency decrease. The photo peak relative efficiency increasing with increasing and also the total relative efficiency same behavior