分类: 物理学 >> 核物理学 提交时间: 2023-10-07
摘要: In the RD for upgrading the KL0and detector (KLM) in Belle II experiment using scintillator and silicon photomultiplier (SiPM), we design a compact preamplifier with high#2;speed and low-noise. The preamplifier has a good gain stability, a baseline noise level of 0.3 mV, a good time resolution that can achieve < 20 ps, and can be applied comprehensively to SiPMs. To reduce the pile-up in using a large size SiPM or an array of SiPMs, which is due to the large capacitance and high dark count rate, we adopt pole#2;zero-cancellation which reduce both the rise time and the fall time of a SiPM signal. The combinations of the preamplifier and several kinds of SiPMs show time resolutions better than 50 ps for most of the cases; when the number of detected photons is larger than 60, a time resolution of about 25 ps can be achieved
分类: 物理学 >> 核物理学 分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2023-09-12
摘要: The neutron capture cross sections (${n, upgamma}$) of Bromine was performed with the time-of-flight (TOF) technique at the Back-n facility of the China Spallation Neutron Source (CSNS). Prompt $ upgamma$-rays originating from neutron-induced capture events were detected by four C${}_6$D${}_6$ detectors. The pulse height weighting technique (PHWT) and the double-bunch unfolding method based on the Bayesian theory were used in the data analysis. To obtain reliable measurement results, background deductions, normalization, and corrections were carefully considered. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in unresolved resonance region the was obtained from 10 to 400 keV. The experimental results were compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. The TALYS code was used to describe the average cross sections in the unresolved resonance region. Astrophysical Maxwell average cross sections (MACSs) of ${}^{79,81}$Br from $ kT $ = 5 to 100 keV was calculated over a sufficiently wide range of neutron energies. At a thermal energy of $kT=30$ keV, the MACS value for ${}^{79}$Br 638$ pm$64 mb is in good agreement with the KADoNiS recommended value. By contrast, the value of 293$ pm$29 mb for ${}^{81}$Br is substantially higher than those of the evaluated database and the KADoNiS recommended value.