Precision Gamma-ray Spectroscopy of Fission Fragments

The decay data on fission fragments plays an important role in non-proliferation and reactor science, and forms the foundation for many fission yield measurements.  Many isotopes, however, were last studied at a time when gamma-ray spectroscopy was in its infancy.  A new campaign of measurements to improve decay data related to fission fragments will be described.  It involves measurements using the Gammasphere array at Argonne National Laboratory as well as a new detector system being built at Brookhaven National Laboratory.   Capabilities and initial commissioning of the new detector system will be presented.  A fission fragment of interest is ¹⁴⁰La, a well-known nuclear chronometer and particulate fission fragment monitored as part of  CTBTO. A source of ¹⁴⁰La was produced through neutron irradiation at UMASS, Lowell and studied with Gammasphere.  Preliminary results on the measurement of precision intensities will be presented.