Improving Decay Data for Fission Product Nuclei through High-Precision Measurements*

For national security applications, such as stockpile science and nuclear forensics, a straightforward and reliable method to determine the number of fissions in a chain reaction is to detect emitted γ rays. This presentation focuses on our efforts to improve the nuclear decay data essential for several key fission products. We report high-precision results for the absolute γ-ray emission intensities following the β decays of ⁹⁵Zr, ¹⁴⁴Ce, ¹⁴⁷Nd, and ¹¹¹Ag, achieving a precision of ~ 1% for the highest-intensity transitions. Our methodology involves implanting fission-product samples into a thin carbon foil using lowenergy mass-separated ion beams from the CARIBU facility, followed by β counting with a custom-made 4π gas proportional counter in coincidence with γ-ray spectroscopy utilizing the precisely calibrated HPGe detector at Texas A&M University. We will also discuss our plans to measure the decays of short-lived fission products at nuCARIBU using Gammaspere/X-Array.