Neutron radiography (NR) is a non-destructive evaluation method for detecting the presence of hydrogenous and other neutron absorbing compounds present inside sealed metal enclosures. Most of the explosives used in pyro devices are hydrogenous or contains boron. Detection of such compounds at its location becomes very critical when it has a specified function to perform such as cable cutting in satellites, stage separation in launch vehicles etc. Hence NR is a mandatory inspection technique for many of the pyro devices used in launch vehicles and satellites. Absence of explosive will lead to failure in the predefined action to be performed by the device. The paper concentrates on detection and the possible extent of characterisation of various neutron absorbing compounds when they are present in metal shells of variable sizes. The experiments are carried out using a low-flux deuterium–tritium (accelerator based) neutron source, a moderator-collimator set up developed indigenously to suit the low flux source and a 12 bit cooled CCD based neutron imaging camera. The study shows typical grayscale value ranges for various compounds present in same volume inside the metallic shell of variable wall thickness. Experiments carried out with specimens made of SS304 material having microscopic absorption cross-section of 13.9 barns per molecule and Aluminium of 1.62 barns per molecule shows the effect of variable microscopic cross-sections offered by the metallic cases and variable wall thickness on the grayscale value obtained. Attenuation chart for various compounds when present inside metallic casings are prepared which shows a typical grayscale value range for various thicknesses. Results also show a difficulty in distinguishing compounds having similar range of macroscopic cross-sections. From the present study, it can be established that it is possible to distinguish low dense materials such as chalk powder of macroscopic cross-section 0.13 cm −1 from compounds such as sucrose of macroscopic cross-section 1.63 cm −1 when present inside metal devices. The study focuses on the limitations of an accelerator based low flux neutron radiography setup.

中文翻译：

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通过中子射线照相术检测和表征空间应用中使用的金属器件内部的低密度电荷

中子射线照相 (NR) 是一种无损评估方法，用于检测密封金属外壳内是否存在含氢化合物和其他中子吸收化合物。火爆装置中使用的大多数炸药都是含氢的或含有硼的。当此类化合物具有特定功能时，在其位置检测此类化合物变得非常关键，例如卫星中的电缆切割、运载火箭中的级分离等。因此，NR 是运载火箭中使用的许多热释装置的强制性检测技术，卫星。没有爆炸物将导致设备执行的预定动作失败。该论文集中讨论了各种中子吸收化合物存在于不同尺寸的金属壳中时的检测和可能的表征范围。这些实验是使用低通量氘氚（基于加速器）中子源、为适应低通量源而自行开发的减速器-准直器装置和基于 12 位冷却 CCD 的中子成像相机进行的。该研究显示了不同壁厚金属壳内相同体积中存在的各种化合物的典型灰度值范围。用 SS304 材料制成的试样进行的实验显示，由金属外壳提供的可变微观横截面和可变壁厚对获得的灰度值的影响为 13.9 barns/分子的微观吸收截面和 1.62 barns 的铝. 准备了存在于金属外壳内的各种化合物的衰减图表，该图表显示了各种厚度的典型灰度值范围。结果还表明难以区分具有相似宏观横截面范围的化合物。从目前的研究中可以确定，当存在于金属设备中时，可以将低密度材料（例如宏观横截面为 0.13 cm -1 的白垩粉）与宏观横截面为 1.63 cm -1 的蔗糖等化合物区分开来. 该研究侧重于基于加速器的低通量中子射线照相装置的局限性。可以确定，当存在于金属器件中时，可以将低密度材料（例如宏观横截面为 0.13 cm -1 的白垩粉）与宏观横截面为 1.63 cm -1 的蔗糖等化合物区分开来。该研究侧重于基于加速器的低通量中子射线照相装置的局限性。可以确定的是，当存在于金属器件中时，可以将低密度材料（例如宏观横截面为 0.13 cm -1 的白垩粉）与宏观横截面为 1.63 cm -1 的蔗糖等化合物区分开来。该研究侧重于基于加速器的低通量中子射线照相装置的局限性。