Abstract Recently we have presented direct experimental evidence for large defect clusters being formed in primary damage cascades in self-ion irradiated tungsten [Yi et al., EPL 110:36001 (2015)]. This large size is significant, as it implies that strong elastic interaction between the defects will affect their subsequent evolution, especially if defects are formed close together. Here we present a direct experimental observation of the separation between visible defects in self-ion irradiated tungsten, in the form of a 2d pairwise radial distribution function extracted from transmission electron micrographs (TEM). We also present a detailed analysis of the observed radial distribution function, and infer the probable size and shape of individual cascades. We propose and validate a simple exponential form for the spatial distribution of defects within a single cascade. The cascade statistics necessary have been acquired by developing an automated procedure for analysing black-dot damage in TEM micrographs. We confirm that the same model also produces a high-quality fit to the separation between larger defects observed in MD simulations. For the first time we present experimental evidence for the sub-nanometre-scale spatial distribution of defect clusters within individual cascades.

中文翻译：

---

直接观察钨中初级级联损伤的空间分布

摘要 最近，我们提供了在自离子辐照钨的初级损伤级联中形成大缺陷簇的直接实验证据 [Yi 等人，EPL 110:36001 (2015)]。这个大尺寸很重要，因为它意味着缺陷之间的强弹性相互作用将影响它们随后的演变，特别是如果缺陷形成得很近。在这里，我们以从透射电子显微照片 (TEM) 中提取的 2d 成对径向分布函数的形式，对自离子辐照钨中可见缺陷之间的分离进行了直接实验观察。我们还对观察到的径向分布函数进行了详细分析，并推断出单个级联的可能大小和形状。我们提出并验证了单个级联中缺陷空间分布的简单指数形式。通过开发用于分析 TEM 显微照片中的黑点损坏的自动化程序，已经获得了必要的级联统计数据。我们确认，相同的模型也对 MD 模拟中观察到的较大缺陷之间的分离产生了高质量的拟合。我们第一次提供了单个级联中缺陷簇的亚纳米级空间分布的实验证据。