Measuring the 20.2-ms half life of the 472-keV line from the isomer Na-24m with pulsed photons at the Idaho Accelerator Center

Abstract At the Idaho Accelerator Center, we employed a pulsed bremsstrahlung photon beam generated from the 44-MeV, 1300 MHz L-band electron Linac which was then directed onto a 99.9% natural magnesium target (isotopically 10% 25 Mg). We investigated a method of measuring the 20.2 ms half life of the photoproduced 24m Na isomer created in the process: γ  +  25 Mg → p +  24m Na. The telltale 472-keV gamma line was measured between the photon pulses with an HPGe detector shielded within a lead cave. We used an ion chamber for monitoring the photon beam and used a novel arrangement of Zr/Ni foils for ascertaining the angular distribution of the beam profile. We discuss our preliminary results and future plans for extracting photonuclear cross sections.