Measurement of new 228Ac Isomers using a 228Ra doped CeBr3 scintillation crystal

초록

Despite significant research efforts, some of the isomeric states are not fully understood. In this study, we measured the beta and gamma energies, as well as the decay times, of 228Ac isomers produced via the beta decay of 228Ra. To perform these measurements, a 228Ra radioactive source was embedded within a crystal scintillator. Given the low Q-value (45.8 key) of 228Ra beta decay and the correspondingly low energy emissions from the resulting 228Ac isomers, these measurements are inherently challenging. For this purpose, we coated a 228Ra radioactive source inside a quartz ampoule and grew CeBr3 using the Bridgman method, thereby embedding the 228Ra source within the CeBr3 scintillator. The CeBr3 scintillator was selected for its high light yield, good energy resolution, and fast decay time, all of which are advantageous for detecting low-energy signals and measuring short decay times. Since 228Ac is produced through the beta decay of 228Ra, the gamma emission of the isomer coincides with the beta particle. We utilized the delayed coincidence method to measure the energy and decay time of the isomers. The events were categorized based on the number of pulses, such as two-and three-pulse events, depending on the occurrence of the beta and subsequent gamma pulses. By analyzing the energy and decay time of each pulse, individual isomeric states of 228Ac were distinguished.

키워드