Development of the detector system for β-decay spectroscopy at the KEK Isotope Separation System

摘要

The KEK Isotope Separation System has been developed to study the β-decay properties of the neutron-rich nuclei around the neutron magic number N = 126. These properties are essential for understanding the origin of the third peak in the r-process element abundance pattern. The detector system for β-decay spectroscopy at the KEK Isotope Separation System should have high detection efficiency for low-energy β-rays, and should be operated under a low-background environment. The detector system of the KEK Isotope Separation System consists of β-ray telescopes and a tape transport system. The solid angle covered by the β-ray telescopes is as large as 75% of 4π in total. The Q_β-value dependence of the detection efficiency was estimated by Geant4 simulation. The background rate was 0.09 cps using a veto counter system and Pb shields. This background rate allows us to measure the lifetime of ~(202)Os.