Maeda Makoto, Segawa Mariko, Toh Yosuke, Endo Shunsuke, Nakamura Shoji, Kimura Atsushi
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan.
Sci Rep. 2022 Jun 1;12(1):6287. doi: 10.1038/s41598-022-08594-2.
A high-accuracy analytical method is broadly required to obtain reliable research results. Thus, prompt γ-ray analysis (PGA), one of the most accurate non-destructive analytical methods, has been employed in various fields. However, the measurement accuracy of PGA is also known to degrade in hydrogenous samples. The degradation is caused by variation in the measurement sensitivity (counts per milligram) following the change in neutron energy due to scattering with hydrogen nucleus. Number of scatterings is well known to depend on the hydrogen content in a sample. However, considering multiple scatterings, hydrogen density, which has not been taken into account as yet, may also lead to the accuracy degradation. Here, we show the effect of the hydrogen density in PGA by evaluating the measurement sensitivity of samples with the same hydrogen content and different densities. We find that the measurement sensitivity varies by more than 30% depending on the hydrogen density even at the same hydrogen content. The variation is a particularly serious problem for PGA requiring a few percent accuracy in most cases. Additionally, although the variation is apparently observed in hydrogenous samples, the similar phenomenon can occur in other nuclides with a large scattering cross section; it may affect nuclear cross-section measurements using neutrons in such fields as astrophysics and nuclear energy.
为了获得可靠的研究结果，广泛需要一种高精度的分析方法。因此，瞬发γ射线分析（PGA）作为最精确的非破坏性分析方法之一，已被应用于各个领域。然而，众所周知，PGA在含氢样品中的测量精度也会下降。这种下降是由于与氢核散射导致中子能量变化后测量灵敏度（每毫克计数）的变化引起的。众所周知，散射次数取决于样品中的氢含量。然而，考虑到多次散射，尚未考虑的氢密度也可能导致精度下降。在这里，我们通过评估具有相同氢含量和不同密度的样品的测量灵敏度，展示了PGA中氢密度的影响。我们发现，即使在相同的氢含量下，测量灵敏度也会因氢密度而变化超过30%。对于大多数情况下要求精度达到百分之几的PGA来说，这种变化是一个特别严重的问题。此外，尽管在含氢样品中明显观察到这种变化，但在其他具有大散射截面的核素中也可能出现类似现象；它可能会影响天体物理学和核能等领域中使用中子进行的核截面测量。
