ANTARES冷中子束线上的时间分辨中子成像
Time-resolved neutron imaging at ANTARES cold neutron beamline
摘要：
在用X射线进行的非破坏性评价中，嵌入致密、重（或高Z）基质中的轻元素显示出很少的对比度，并且它们的结构细节几乎不能被揭示。另一方面，中子射线照相术为这些情况提供了解决方案，特别是对于含氢材料，这是由于氢的大的中子散射截面和中子截面对原子序数的不相关依赖性。目前，大多数中子成像实验都是用静态物体进行的，这主要是由于中子束线设施的通量强度有限，有时也是由于探测器的限制。然而，有些应用需要动态现象的研究，现在可以在几个高强度光束线，如最近重建的ANTARES光束线在FRM-II反应堆进行。在本文中，我们展示了时间分辨成像的能力，重复的过程中，不同阶段的过程可以同时成像，并集成在多个周期。利用快MCP/Timepix中子计数探测器对10 Hz频率下运行的蒸汽机模型内的水分布进行了成像。在<10分钟的积分内，以亚毫米的空间分辨率测量水的量作为循环时间的函数，从而证明了时间分辨中子射线照相术用于未来应用的能力。ANTARES束线的中子谱以及铁样品的透射谱也测量与飞行时间（TOF）技术结合高分辨率束斩波器。我们的装置的能量分辨率被发现是~0.8%，在5 meV和~1.7%，在25 meV。
英文摘要：
In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and integrated over multiple cycles. A fast MCP/Timepix neutron counting detector was used to image the water distribution within a model steam engine operating at 10 Hz frequency. Within <10 minutes integration the amount of water was measured as a function of cycle time with a sub-mm spatial resolution, thereby demonstrating the capabilities of time-resolved neutron radiography for the future applications. The neutron spectrum of the ANTARES beamline as well as transmission spectra of a Fe sample were also measured with the Time Of Flight (TOF) technique in combination with a high resolution beam chopper. The energy resolution of our setup was found to be ~0.8% at 5 meV and ~1.7% at 25 meV.
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