Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

Area of Science:

• Nuclear Physics
• Reactor Physics
• Particle Physics

Background:

• Reactor antineutrino spectra are crucial for nuclear non-proliferation and fundamental physics.
• Recent measurements show discrepancies with theoretical models, particularly in the 5-8 MeV range.
• The decay of 92Rubidium ((92)Rb) is a significant contributor to this spectral region, but its properties are uncertain.

Purpose of the Study:

• To precisely measure the decay properties of (92)Rubidium using total absorption spectroscopy.
• To investigate previously unobserved beta feeding in the (92)Rb decay.
• To assess the impact of refined (92)Rb decay data on calculated reactor antineutrino spectra.

Main Methods:

• Total absorption spectroscopy was employed to study the beta decay of (92)Rubidium.
• High-resolution measurements were performed to identify beta feeding distributions.
• The influence of new data on the summation method for antineutrino spectrum calculation was analyzed.

Main Results:

• Previously unobserved beta feeding in the 4.5-5.5 MeV region of the (92)Rb decay was identified.
• The ground-state to ground-state (GS-to-GS) feeding for (92)Rb was determined to be 87.5(25)%.
• These refined decay properties significantly alter the predicted reactor antineutrino spectrum.

Conclusions:

• The revised (92)Rb decay data resolve some inconsistencies between measured and calculated reactor antineutrino spectra.
• Accurate knowledge of fission product decay properties is essential for precise antineutrino flux predictions.
• This study contributes to a better understanding of reactor antineutrino physics and its applications.