A five-HPGe detector system for γ−γ angular correlation measurements for mass-separated short-lived nuclei

A multiple-detector system for γ−γ angular correlation measurements has been constructed to study low-spin states populated via the β-decay of mass-separated short-lived nuclei using an isotope separator on-line. The system consists of five-HPGe detectors which are configured at fixed angles to provide ten correlation angles of 90°, 100°, 110°, 120°, 130°, 130°, 140°, 150°, 160° and 170° simultaneously, and with short source-to-detector distance to enlarge the detection efficiencies. The performance of the system was studied with an 152Eu source in off-line experiments. The contribution of finite solid angle of detectors, random coincidences and Compton-scattered γ-rays were appropriately corrected. Difference in the coincidence efficiency among various detector pairs was experimentally evaluated, and it was concluded that this difference was almost negligible in this system. In an on-line experiment, low-spin states in 126Ba populated via the β+-decay of 126La were investigated with this system.