This article presents the development, full-characterization, and in-core testing of a miniature neutron detector for the investigation of highly localized in-core neutronics effects in the zero-power reactor CROCUS, operated at the École Polytechnique fédérale de Lausanne (EPFL), Switzerland. A ZnS: 6LiF screen, mixing inorganic scintillator and neutron converter, with a surface of 1 mm2 and a thickness of 0.2 mm, was coupled with a silicon photomultiplier (SiPM) via a 10-m optical fiber. Analog readout electronics were adopted in this prototype version to process the SiPM output signal. A first campaign was carried out to assess the detection system capabilities in terms of neutron detection and counting in mixed neutron-gamma radiation fields. The miniature detector was thoroughly characterized with a Pu-Be source installed in the CARROUSEL facility and was subsequently tested inside a control rod guide tube of the CROCUS reactor in different reactor conditions, i.e., at shutdown, startup, and critical. The detector shows a linear response with a reactor power increase up to 6.5 W (i.e., around $10 {^{\mathrm{ 8}}}\,\,\text {cm}^{-2}\cdot \text {s}^{-1} $ total neutron flux) and excellent neutron counting capabilities, when compared to other localized detection systems available in CROCUS, such as the miniature fission chambers and single-crystal vapor deposited (sCVD) diamond detectors. In addition, the exposure of the miniature detector to a 60Co source with an activity of ~250 GBq, combined with the computation of the gamma flux in CROCUS with the Serpent 2 Monte Carlo code, confirmed the gamma insensitivity of the system in a mixed neutron-gamma field.

中文翻译：

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用于 CROCUS 芯内热中子探测的 mm3 光纤耦合闪烁体

本文介绍了微型中子探测器的开发、全面表征和堆内测试，用于研究在洛桑联邦理工学院 (EPFL) 运行的零功率反应堆 CROCUS 中高度局部化的堆芯中子学效应， 瑞士。ZnS：6LiF 屏幕，混合无机闪烁体和中子转换器，表面为 1 mm2，厚度为 0.2 mm，通过 10 米光纤与硅光电倍增管 (SiPM) 耦合。该原型版本采用模拟读出电子设备来处理 SiPM 输出信号。开展了第一次活动，以评估探测系统在混合中子-伽马辐射场中的中子探测和计数方面的能力。微型探测器通过安装在 CARROUSEL 设施中的 Pu-Be 源进行了彻底的表征，随后在 CROCUS 反应堆的控制棒导管内在不同的反应堆条件下进行了测试，即在关闭、启动和临界状态下。探测器显示出线性响应，反应堆功率增加到 6.5 W（即大约 $10 {^{\mathrm{ 8}}}\,\,\text {cm}^{-2}\cdot \text {s }^{-1} $ 总中子通量）和出色的中子计数能力，与 CROCUS 中可用的其他局部检测系统相比，例如微型裂变室和单晶气相沉积 (sCVD) 金刚石探测器。此外，将微型探测器暴露于活度约为 250 GBq 的 60Co 源，结合使用 Serpent 2 Monte Carlo 代码计算 CROCUS 中的伽马通量，