In the field of neutron scattering science, a large variety of instruments require detectors for thermal and cold neutrons. Helium-3 has been one of the main actors in thermal and cold neutron detection for many years. Nowadays, neutron facilities around the world are pushing their technologies to increase the available flux delivered at the instruments; this enables a completely new science landscape. Complementary with the increasing available flux, a better signal-to-background (S/B) ratio enables to perform new types of measurements. For instance, in neutron reflectometry, the time resolution for kinetic studies is limited by the available S/B. An improved S/B opens the possibility of sub-second kinetic studies. To this aim, this manuscript re-examines the background sensitivity of today’s “gold standard” neutron detection. Fast neutrons and gamma rays are the main background species in neutron scattering experiments. The efficiency (sensitivity) of detecting fast neutrons, cosmic rays and gamma rays, for a Helium-3-based detector is studied here through the comparison with Helium-4 counters. The comparison with Helium-4 allows to separate the thermal (and cold) neutron from the fast neutron contributions in Helium-3-based counters which are otherwise entangled, verifying previous results from an indirect method. A relatively high sensitivity is found. Moreover, an estimate for the cosmic neutron fluence, also a source of background, at ground level at ESS is presented in this manuscript.

中文翻译：

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通过与He-4探测器进行比较来验证He-3比例计数器的快速中子灵敏度

在中子散射科学领域，各种各样的仪器需要用于热中子和冷中子的探测器。多年来，氦3一直是热中子和冷中子检测的主要参与者之一。如今，世界各地的中子设施都在推动其技术发展，以增加仪器提供的可用通量。这使科学界焕然一新。与可用通量的增加互补，更好的信噪比（S / B）使执行新型测量成为可能。例如，在中子反射法中，动力学研究的时间分辨率受到可用S / B的限制。改进的S / B开启了亚秒级动力学研究的可能性。为此，该手稿重新审查了当今“金标准”中子检测的背景敏感性。快中子和伽马射线是中子散射实验中的主要背景物质。通过与氦4计数器的比较，研究了基于氦3的探测器对快中子，宇宙线和伽马射线的探测效率（灵敏度）。与氦4的比较可以将基于热氦的3中子中的热中子和冷中子从快速中子中分离出来，否则它们会纠缠在一起，从而验证了间接方法的先前结果。发现相对较高的灵敏度。此外，本文还对ESS地面上的宇宙中子注量进行了估算，这也是背景的来源。通过与Helium-4计数器进行比较，研究了基于Helium-3的探测器的结构。与氦4的比较可以将基于热氦的3中子中的热中子和冷中子与快速中子的贡献区分开，否则它们会纠缠在一起，从而验证了间接方法的先前结果。发现相对较高的灵敏度。此外，本文还对ESS地面上的宇宙中子注量进行了估算，这也是背景的来源。通过与Helium-4计数器进行比较，研究了基于Helium-3的探测器的结构。与氦4的比较可以将基于热氦的3中子中的热中子和冷中子与快速中子的贡献区分开，否则它们会纠缠在一起，从而验证了间接方法的先前结果。发现相对较高的灵敏度。此外，本文还对ESS地面上的宇宙中子注量进行了估算，这也是背景的来源。