Facilities and Methods: High-Resolution Gamma-Ray Spectroscopy at TRIUMF-ISAC

Abstract

It is no accident that the rapid technical evolution of radioactive beam facilities has coincided with challenges to the standard models of nuclear structure and fundamental interactions. In nuclear structure, the shell model is a de facto standard model. The properties and systematics of nuclei near stability are well understood in terms of the magic nucleon numbers at shell closures. However, when confronted with experimental data on increasingly exotic nuclei, the model fails. The near-stability magic nucleon numbers disappear, and new ones emerge [1]. This is evidenced for example by the energies and γ transition rates of excited states. These excitations may be probed by reactions induced with accelerated radioactive beams, or by a parent β decay. At the same time, high production yield for selected isotopes allows for very high precision measurements of specific decay processes. Because β decay is a nuclear manifestation of the weak interaction, high precision measurements of nuclear β decay provide a strict test of fundamental symmetries [2].