Abstract The simultaneous occurrence of two double-strand breaks in spatially separated locations on the DNA molecule can cause the loss of a whole DNA loop. The length of the lost DNA loop depends on the geometrical position of the two damaged sites and on the degree of damage in sites of several nanometres in size. As they are more prone to produce complex ionisation clusters in such sites, densely ionising charged particles are expected to produce more spatially correlated ionisation clusters than electrons and photons. In this work, correlations in the production of ionisation clusters in two spatially separated sites were investigated for the first time in detail by nanodosimetric measurements in 1.2 mbar H2O, 1.2 mbar C3H8 and 1.2 mbar C4H8O using alpha particles from a 241Am source. The results show that there are irradiation geometries where only weak correlation exists between the probabilities for ionisation clusters in the two spatially separated sites, e. g. when the primary beam passes one site centrally. In general, however, the two probability distributions are not statistically independent, for instance if both sites are irradiated in a broad beam.

中文翻译：

---

241Am α 粒子轨道结构中两个空间分离的纳米体积中的相关电离：使用 PTB 离子计数器进行测量

摘要 在 DNA 分子上空间分离的位置同时发生两条双链断裂会导致整个 DNA 环的丢失。丢失的 DNA 环的长度取决于两个损坏位点的几何位置和几个纳米大小的位点的损坏程度。由于它们更容易在这些位置产生复杂的电离团簇，因此预计密集电离的带电粒子会产生比电子和光子更多的空间相关电离团簇。在这项工作中，首次通过使用来自 241Am 源的 α 粒子在 1.2 毫巴 H2O、1.2 毫巴 C3H8 和 1.2 毫巴 C4H8O 中进行纳米剂量测量，详细研究了两个空间分离位点中电离簇产生的相关性。结果表明，存在辐射几何结构，其中两个空间分离位置的电离簇的概率之间仅存在微弱的相关性，例如当主光束通过一个中心位置时。然而，一般来说，这两个概率分布在统计上不是独立的，例如，如果两个位置都受到宽光束照射。