학술논문
Total absorption $\gamma$-ray spectroscopy of the $\beta$ decays of $^{96\text{gs,m}}$Y
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Working Paper
Author
Guadilla, V.; Meur, L. Le; Fallot, M.; Briz, J. A.; Estienne, M.; Giot, L.; Porta, A.; Cucoanes, A.; Shiba, T.; Zakari-Issoufou, A. -A.; Algora, A.; Tain, J. L.; Agramunt, J.; Jordan, D.; Monserrate, M.; Montaner-Pizá, A.; Nácher, E.; Orrigo, S. E. A.; Rubio, B.; Valencia, E.; Äystö, J.; Eronen, T.; Gorelov, D.; Hakala, J.; Jokinen, A.; Kankainen, A.; Kolhinen, V.; Koponen, J.; Moore, I.; Penttilä, H.; Pohjalainen, I.; Reinikainen, J.; Reponen, M.; Rinta-Antila, S.; Rytkönen, K.; Sonnenschein, V.; Voss, A.; Fraile, L. M.; Vedia, V.; Ganioğlu, E.; Gelletly, W.; Lebois, M.; Wilson, J. N.; Martinez, T.; Sonzogni, A. A.
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Abstract
The $\beta$ decays of the ground state (gs) and isomeric state (m) of $^{96}$Y have been studied with the total absorption $\gamma$-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility. The separation of the 8$^{+}$ isomeric state from the 0$^{-}$ ground state was achieved thanks to the purification capabilities of the JYFLTRAP double Penning trap system. The $\beta$-intensity distributions of both decays have been independently determined. In the analyses the de-excitation of the 1581.6 keV level in $^{96}$Zr, in which conversion electron emission competes with pair production, has been carefully considered and found to have significant impact on the $\beta$-detector efficiency, influencing the $\beta$-intensity distribution obtained. Our results for $^{96\text{gs}}$Y (0$^+$) confirm the large ground state to ground state $\beta$-intensity probability, although a slightly larger value than reported in previous studies was obtained, amounting to $96.6_{-2.1}^{+0.3}\%$ of the total $\beta$ intensity. Given that the decay of $^{96\text{gs}}$Y is the second most important contributor to the reactor antineutrino spectrum between 5 and 7 MeV, the impact of the present results on reactor antineutrino summation calculations has been evaluated. In the decay of $^{96\text{m}}$Y (8$^{+}$), previously undetected $\beta$ intensity in transitions to states above 6 MeV has been observed. This shows the importance of total absorption $\gamma$-ray spectroscopy measurements of $\beta$ decays with highly fragmented de-excitation patterns. $^{96\text{m}}$Y (8$^{+}$) is a major contributor to reactor decay heat in uranium-plutonium and thorium-uranium fuels around 10 s after fission pulses, and the newly measured average $\beta$ and $\gamma$ energies differ significantly from the previous values in evaluated databases (...)