Abstract Shadowgraphy and X-ray phase contrast (XPC) imaging are two techniques that are used for characterizing the deuterium-tritium ice layer in inertial confinement fusion targets. Each technique has limitations that affect how accurately they can characterize small crystalline defects and measure the ice thickness nonuniformities that may be only a few micrometers in height. The concern is that shadowgraphy may be overly sensitive to the shape and depth of defects in the ice surface and insufficiently sensitive to the shape of longer wavelength roughness, while XPC may be too insensitive to defects in the ice surface. Multiple ice layers with different thicknesses (40 to 63 μm), thickness uniformities (peak-to-valley variations that range from < 2 to 12 μm), and crystal defects were analyzed using shadowgraphy and XPC techniques. The results from each method agree when the ice layer is uniformly thick and the crystal lacks defects. That agreement worsens as the number of defects in the surface of the ice layer increases, and the roughness (that is determined from a shadowgram image of the target’s limb) becomes greater than can be justified by the number of defects that are seen in the target’s front and rear surfaces. The XPC technique is considerably less sensitive to surface defects, in part because of the poorer dynamic range and image resolution compared to shadowgraphy. Localized regions of the ice layer that are thicker or thinner than the average thickness of the layer are reported by shadowgraphy to be smaller in height and footprint (by up to 30%) than by XPC. As a result, the two techniques report different ice layer thicknesses that can vary by up to 10%. Shadowgraphy, which results from two caustics that trace different paths through the target, and in theory, image the same ice/vapor surface (but reflect from either the vapor or ice side of the interface), did not consistently characterize the size or shape of ice features to be the same magnitude. The XPC technique provides the best assessment of low-mode (l < 7) roughness in the ice layer. Shadowgraphy results using the strongest caustic is best for detecting the presence of grooves in the ice, although not for quantifying the size of them. If multiple grooves are present, it is best to discard and reform the ice layer.

中文翻译：

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用于表征惯性约束聚变目标中的 DT 冰层的阴影成像和 X 射线相位对比方法的比较

摘要 阴影成像和 X 射线相衬 (XPC) 成像是两种用于表征惯性约束聚变目标中氘-氚冰层的技术。每种技术都有局限性，这些局限性会影响它们表征小晶体缺陷和测量可能只有几微米高的冰厚度不均匀性的准确性。令人担忧的是，阴影成像可能对冰面缺陷的形状和深度过于敏感，对较长波长粗糙度的形状不够敏感，而 XPC 可能对冰面缺陷太不敏感。使用阴影法和 XPC 技术分析了具有不同厚度（40 至 63 微米）、厚度均匀性（峰谷变化范围从 < 2 至 12 微米）和晶体缺陷的多个冰层。当冰层厚度均匀且晶体没有缺陷时，每种方法的结果都一致。随着冰层表面缺陷数量的增加，这种一致性变得更糟，粗糙度（由目标肢体的阴影图图像确定）变得比目标肢体中看到的缺陷数量所能证明的还要大。前表面和后表面。XPC 技术对表面缺陷的敏感度要低得多，部分原因是与阴影成像相比，动态范围和图像分辨率较差。冰层的局部区域比冰层的平均厚度更厚或更薄，根据阴影成像报告，其高度和足迹比 XPC 小（最多 30%）。因此，这两种技术报告了不同的冰层厚度，其变化幅度可达 10%。阴影成像是由跟踪穿过目标的不同路径的两个焦散产生的，理论上，成像相同的冰/蒸汽表面（但从界面的蒸汽或冰侧反射），并没有一致地表征目标的大小或形状冰特征是相同的量级。XPC 技术提供了冰层中低模 (l < 7) 粗糙度的最佳评估。使用最强焦散的阴影成像结果最适合检测冰中是否存在凹槽，但不能量化它们的大小。如果存在多个凹槽，最好丢弃并重新形成冰层。没有一致地将冰特征的大小或形状描述为相同的量级。XPC 技术提供了冰层中低模 (l < 7) 粗糙度的最佳评估。使用最强焦散的阴影成像结果最适合检测冰中是否存在凹槽，但不能量化它们的大小。如果存在多个凹槽，最好丢弃并重新形成冰层。没有一致地将冰特征的大小或形状描述为相同的量级。XPC 技术提供了冰层中低模 (l < 7) 粗糙度的最佳评估。使用最强焦散的阴影成像结果最适合检测冰中是否存在凹槽，但不能量化它们的大小。如果存在多个凹槽，最好丢弃并重新形成冰层。