Beta-Decay studies at TRIUMF-ISAC using the GRIFFIN spectrometer
The Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the TRIUMF-ISAC facility is comprised of 16 large-volume high-purity germanium clover detectors coupled with a powerful suite of ancillary detector systems and a custom-built digital data acquisition system. The absolute singles photo-peak efficiency approaches 17% at 1.3MeV. The ancillary detector systems presently available include the SCEPTAR array of plastic scintillators for beta-tagging, the PACES array of in-vacuum, LN2-cooled Si(Li) diodes for high-resolution internal conversion electron spectroscopy and an array of LaBr3 scintillators for fast gamma-ray timing measurements. In addition, GRIFFIN has can be combined with the DESCANT neutron array to enable studies of beta-delayed neutron emitting nuclei relevant to the astrophysical r-process.
First experiments have been completed with GRIFFIN following its commissioning in September 2014. The competition between different astrophysical production mechanisms of 116Cd has been investigated through a detailed study of the excited states in 115Cd. A beta-decay study of 32Na at the centre of the island of inversion will help characterize the excitations in 32Mg. High-statistics beta decay studies using radioactive beams of K isotopes have been made of the excited states in 46Ca and 47Ca in order to test modern theoretical calculations. The decay properties of Cd isotopes in the vicinity of doubly-magic 132Sn have been investigated in order to solidify our understanding of astrophysical r-process flow in this region.
The GRIFFIN facility will greatly enhance the capabilities in the nuclear structure, nuclear astrophysics and fundamental symmetries research programs with stopped radioactive beams available from ISAC and in the future ARIEL. An overview of the GRIFFIN spectrometer and the first experimental results will be presented.