NaI (TI)-plastic summing technique for energy identification in picosecond nuclear lifetime measurement

A delayed-coincidence spectrometer system was developed to measure nuclear lifetimes in the picosecond region by the centroid-shift method. liming signals were derived from two plastic scintillators. A specially constructed NaI(Tl) detector was used to detect the gamma-rays which were Corrpton-scattered from one of the plastic scintillators. Energy identification was achieved by sumning the signals from the plastic detector and the NaI(Tl) detector to give the full energy photopeaks. In order to test the effectiveness of the system, the mean lives of the first excited states of Ni60 and Ba134 were measured. The 1.0-psec mean life in Ni60 could not be measured with the present system. The gamma-gamma and beta-gamma coincidence experiments gave the mean life of the first excited state of Ba134 as 6.1 ±0.8 psec and 4.8 ±0.6 psec, respectively. It is concluded that the shortest mean life that can reliably be measured by the present system is about 5 psec.Ball State UniversityMuncie, IN 47306Thesis (M.S.)--Ball State University, 1973