Improving Direct Beta Energy Spectra Measurements with Total Absorption Spectroscopy*

Precision measurements of beta-decay energy spectra have been of recent interest. Precision measurements of the beta energy spectrum can provide insight into the nuclear matrix elements of the parent and daughter nuclei involved as well as place constraints on the coupling constants of the beta-decay operator. Precision measurements of the beta energy spectrum are also of interest to both reactor antineutrino predictions as the exact spectral shape is directly correlated to the energy distribution of emitted antineutrino. The same spectral shape directly influences the average emitted beta energy independently from the beta-feeding intensities and therefore has implications for reactor decay heat. If bremsstrahlung radiation emitted by the beta particles interacting with the surrounding detector volume is not recaptured, a bias in the spectral shape for more low energy betas develops and subsequently causes an overprediction of high energy antineutrinos. Therefore integral measurements of both the beta radiation and gamma radiation are vital to constraining the spectral shape of the emitted beta particle. Recent integral measurements of both the beta energy spectrum and emitted gamma radiation of various isotopes have been performed with the Modular Total Absorption Spectrometer and will be presented.