Enhanced Performance of Small Angle Neutron Scattering at the McMaster Nuclear Reactor

这项研究工具和仪器拨款申请的目的是提高麦克马斯特核反应堆(MNR)的“纳米材料的小角中子散射”(MacSANS)仪器的性能。这台中子散射仪目前正在完成建造。2021年投入使用后，它将成为加拿大仅有的两台中子散射仪器之一(另一台是MNR的MAD中子衍射仪)。这项RTI授权应用程序将使MacSANS仪器的性能得到增强，这将通过对原始设计进行两次修改来实现： (1)我们将充分利用仪器的大探测器容器，允许1平方米的位置灵敏中子探测器垂直平移，最大可达0.5米。这一改进将使仪器的长度-标度灵敏度提高约130%，使仪器的动量转移范围Q或散射角范围增加约50%； 和 (2)我们将通过用单晶铅过滤器取代仪器主飞行路径中的多晶铅聚集体过滤器来增加中子通量。铅是减少入射中子束中的伽马辐射所必需的。然而，目前的多晶铅聚集体也会衰减所需的中子束强度，除非入射中子束的波长大于铅的布拉格截止波长，后者约为6。这样做的净效果是，多晶铅聚集体滤光器将入射中子束限制为波长大于~6的中子，而配置适当的单晶铅滤光器可以用于任何波长的中子。例如，MacSANS仪器在入射波长为~4的情况下运行，将允许扩大Q或散射角，覆盖范围，并增加入射中子束的通量，最高可达~4倍。这两项改进加在一起，将扩大仪器的Q范围和提高其中子强度。因此，这些改进将提高仪器在被探测材料的纳米尺度的信号和动态范围方面的灵敏度。 我们试图通过这一RTI应用程序对MacSANS仪器进行的改进，将影响到对材料纳米结构感兴趣的加拿大科学家和工程师组成的大型泛加拿大社区。PI和8名共同申请者目前管理着大约74个HQP，他们代表着一个更大的社区，他们将利用这个高度专业化的研究基础设施。这些改进还利用了CFI(300万美元)、ORCDF(300万美元)和麦克马斯特大学(100万美元)之前的约700万美元投资，用于MacSANS的原始设计和建造。

The aim of this Research Tools and Instruments grant application is to enhance the performance of the “Small Angle Neutron Scattering for Nanoscale Materials” (MacSANS) instrument at the McMaster Nuclear Reactor (MNR). This neutron scattering instrument is currently completing construction. When operational in 2021, it will be one of only two neutron scattering instruments in Canada (the other is the MAD neutron diffractometer, also at the MNR). The enhanced performance of the MacSANS instrument, which this RTI grant application will enable, will occur via two modifications to the original design: (1)We will take full advantage of the large detector vessel of the instrument and allow for vertical translation of the 1 m2 position-sensitive neutron detector, by up to 0.5 m. This improvement will extend the instrument's length-scale sensitivity by about 130% by increasing the accessible range of momentum transfer, Q, or scattering angle, range of the instrument by ~ 50%; and (2) We will increase the neutron flux by replacing the polycrystalline lead aggregate filter in the primary flight path of the instrument with a single crystal lead filter. The lead is necessary to reduce the gamma radiation in the incident neutron beam. However, the current polycrystalline lead aggregate also attenuates the desired neutron beam intensity, unless the wavelength of the incident neutron beam is greater than the Bragg cut-off for lead, which is about 6 . The net effect of this is that a polycrystalline lead aggregate filter restricts the incident neutron beam to neutrons with wavelengths greater than ~ 6 , whereas an appropriately configured single crystal lead filter could be used with neutrons of any wavelength. Operation of the MacSANS instrument with incident wavelengths of ~ 4 , for example, would allow both extended Q, or scattering angle, coverage, and also increased incident neutron beam fluxes, of up to factors of ~ 4. Taken together, these two enhancements will increase both the Q range of the instrument and its neutron intensity. Hence these enhancements will increase the sensitivity of the instrument both in terms of the signal and the dynamic range of the length scale of the nanoscale of the material being probed. The enhancements of the MacSANS instrument that we seek to make via this RTI application will impact a large and pan Canadian community of Canadian scientists and engineers with interests in nanostructure in materials. The PI and 8 co-applicants presently supervise some 74 HQP, and are representative of a much larger community who will take advantage of this highly specialized research infrastructure. These enhancements are also leveraging ~ $7M in prior investments by CFI ($3M), ORCDF ($3M) and McMaster University ($1M) for the original design and construction of MacSANS.