The 6LiF-silicon detector array developed for real-time neutron monitoring at white neutron beam at CSNS
The 6LiF-silicon detector array developed for real-time neutron monitoring at white neutron beam at CSNS
复制标题
为 CSNS 的白中子束实时中子监测而开发的 6LiF 硅探测器阵列
DOI：
10.1016/j.nima.2019.162497
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发表时间：
2019-12-01
影响因子：
1.4
通讯作者：
Zhu, Peng
中科院分区：
文献类型：
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作者：
Li, Qiang;Luan, Guangyuan;Zhu, Peng
在中国散裂中子源上建成了一座用于核数据测量的白色中子源并投入运行。我们研制了一台束流监测仪，用于实时在线监测白中子源的中子注量。束流监测器与其他核数据测量探测器同时工作，为数据分析提供中子通量。为了最大限度地减少束流干扰和减小探测器产生的本底，采用了中子转换层和硅探测器分离的结构：在一片10微米的铝箔上沉积了质量厚度为360微克/厘米(2)的(LiF)-Li-6薄膜，并放置在束线内。在束外的薄膜周围放置了8个尺寸为20×20 mm(2)的硅探测器，以最大限度地接收来自转换层的二次粒子，并避免中子束照射。文中描述了束流监测器的模拟(布局、计数率、中子扰动等)、结构和在线性能。在2018年3月CSNS白中子源注量定标实验中，该监测仪取得了良好的在线性能：将30 mm和60 mm束流模式下的束流计数率归一化为100kW的质子束流功率，结果与模拟结果一致。归一化计数率的总不确定度小于1%。此外，还讨论了该监测仪对白中子源10keV以下低能区中子注量率的测量。
A white neutron source for nuclear data measurement has been built and put into operation on China Spallation Neutron Source (CSNS). We developed a beam monitor for real-time online monitoring of neutron flux on the white neutron source. The beam monitor work simultaneously with other nuclear data measurement detectors to provide neutron flux for data analysis. To minimize beam disturbance and reduce the background generated by the monitor, a structure in which neutron conversion layer and Si detectors are separated is employed: A (LiF)-Li-6 film with a mass thickness of 360 mu g/cm(2) was deposited on a 10 mu m aluminum foil and placed inside the beam line. Eight Si-detectors with a size of 20x20 mm(2) were placed around the film outside the beam to maximize the reception of secondary particles from the conversion layer and to avoid neutron beam irradiation. The simulation of the beam monitor (layout, counting rate, neutron disturbance, etc.), construction and online performance are described in the paper. Good online performance of the monitor was achieved during the CSNS white neutron source flux calibration experiment in March, 2018: The counting rate for the beam line operating at Phi 30 mm and Phi 60 mm beam pattern modes was normalized to 100 kW proton beam power, and the result is consistent with the simulation. The total uncertainty of the normalized counting rate is less than 1%. Moreover, the measurement of neutron flux in low energy region below 10 keV of the white neutron source by the monitor is discussed.