Abstract
The accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several studies have shown that the underlying nuclear physics required for the conversion of these spectra into antineutrino spectra is not totally understood. An alternative to such converted spectra is a complementary approach that consists of determining the antineutrino spectrum by means of the measurement and processing of nuclear data. The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gammaray Spectroscopy technique (TAGS). The two main contributors to the Pressurized Water Reactor antineutrino spectrum in the region where the spectral distortion has been observed are ⁹²Rb and ¹⁴²Cs, which have been measured at the radioactive beam facility of the University of Jyvaskyla in two TAGS experiments. We present the results of the analysis of the TAGS measurements of the β-decay properties of ⁹²Rb along with preliminary results on ¹⁴²Cs and report on the measurements already performed.
Highlights
The fission process is at the origin of thermal energy widely used worldwide for electricity production.In general in this process two fission products, that are beta minus emitters, are produced together with a few neutrons
Following the long-recognized reactor anomaly, the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions
The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gammaray Spectroscopy technique (TAGS)
Summary
The fission process is at the origin of thermal energy widely used worldwide for electricity production. It was shown that the data associated with important contributors to the antineutrino spectra could be biased by the Pandemonium effect [3] and require new measurements with the TAGS technique [4] Another method to compute antineutrino spectra from thermal fission of 235U, 239;241Pu was reinvestigated recently, based on the conversion of integral beta spectra measured at the ILL research reactor of Grenoble three decades ago. The three large reactor neutrino experiments Double Chooz, Daya Bay and Reno have shown evidence of shape distortion when their measurements are compared with the antineutrino spectra built with the conversion method, especially in the region 4 to 8 MeV [8]. It is timely to try to improve the predictions of the summation method by reducing the errors associated with the nuclear data
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