Ashenfelter J, Balantekin A B, Band H R, Bass C D, Bergeron D E, Berish D, Bowden N S, Brodsky J P, Bryan C D, Cherwinka J J, Classen T, Conant A J, Cox A A, Davee D, Dean D, Deichert G, Diwan M V, Dolinski M J, Erickson A, Febbraro M, Foust B T, Gaison J K, Galindo-Uribarri A, Gilbert C E, Gilje K E, Hackett B T, Hans S, Hansell A B, Heeger K M, Insler J, Jaffe D E, Ji X, Jones D C, Kyzylova O, Lane C E, Langford T J, LaRosa J, Littlejohn B R, Lu X, Martinez Caicedo D A, Matta J T, McKeown R D, Mendenhall M P, Minock J M, Mueller P E, Mumm H P, Napolitano J, Neilson R, Nikkel J A, Norcini D, Nour S, Pushin D A, Qian X, Romero-Romero E, Rosero R, Sarenac D, Surukuchi P T, Telles A B, Tyra M A, Varner R L, Viren B, White C, Wilhelmi J, Wise T, Yeh M, Yen Y-R, Zhang A, Zhang C, Zhang X
Wright Laboratory, Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
Department of Physics, University of Wisconsin, Madison, Madison, Wisconsin 53706, USA.
Phys Rev Lett. 2019 Jun 28;122(25):251801. doi: 10.1103/PhysRevLett.122.251801.
This Letter reports the first measurement of the ^{235}U ν[over ¯]{e} energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MW{th} highly enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) ν[over ¯]{e}-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to ^{235}U. Despite broad agreement, comparison of the Huber ^{235}U model to the measured spectrum produces a χ^{2}/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured ^{235}U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the ν[over ¯]{e} energy region of 5-7 MeV.
本信函报道了“精确反应堆振荡与能谱实验”（PROSPECT）对²³⁵U反中微子（ν̅ₑ）能谱的首次测量，该实验在距85兆瓦热功率高浓铀（HEU）高通量同位素反应堆7.9米处运行。利用基于表面的分段探测器，PROSPECT观测到31678±304（统计）次由ν̅ₑ引发的逆β衰变，这是迄今为止来自高浓铀裂变的最大样本，其中99%归因于²³⁵U。尽管总体相符，但将休伯²³⁵U模型与测量能谱进行比较时，得到的χ²/自由度 = 51.4/31，主要是由两个局部能量区域的偏差所致。测量得到的²³⁵U能谱形状与预测值相比存在偏差，其大小与在低浓铀动力反应堆5 - 7兆电子伏特的ν̅ₑ能量区域所观测到的偏差相当。
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