Decays of the Three Top Contributors to the Reactor (nu)over-bar(e) High-Energy Spectrum, Rb-92, (96)gsY, and Cs-142, Studied with Total Absorption Spectroscopy

作者：Rasco B C^*; Wolinska Cichocka M; Fijalkowska A; Rykaczewski K P; Karny M; Grzywacz R K; Goetz K C; Gross C J; Stracener D W; Zganjar E F; Batchelder J C; Blackmon J C; Brewer N T; Go S; Heffron B; King T; Matta J T; Miernik K; Nesaraja C D; Paulauskas S V; Rajabali M M; Wang E H; Winger J A; Xiao Y; Zachary C J

来源：Physical Review Letters, 2016, 117(9): 092501.

DOI：10.1103/PhysRevLett.117.092501

We report total absorption spectroscopy measurements of Rb-92, (96)gsY, and Cs-142 beta decays, which are the most important contributors to the high energy (nu) over bar (e) spectral shape in nuclear reactors. These three beta decays contribute 43% of the (nu) over bar (e) flux near 5.5 MeV emitted by nuclear reactors. This (nu) over bar (e) energy is particularly interesting due to spectral features recently observed in several experiments including the Daya Bay, Double Chooz, and RENO Collaborations. Measurements were conducted at Oak Ridge National Laboratory by means of proton-induced fission of U-238 with on-line mass separation of fission fragments and the Modular Total Absorption Spectrometer. We observe a beta-decay pattern that is similar to recent measurements of Rb-92, with a ground-state to ground-state beta feeding of 91(3)%. We verify the 96gsY ground-state to ground-state beta feeding of 95.5(20)%. Our measurements substantially modify the beta-decay feedings of Cs-142, reducing the beta feeding to Ba-142 states below 2 MeV by 32% when compared with the latest evaluations. Our results increase the discrepancy between the observed and the expected reactor (nu) over bar (e) flux between 5 and 7 MeV, the maximum excess increases from similar to 10% to similar to 12%.

• 出版日期2016-8-22