CARR中子深度剖面分析系统设计

Development of neutron depth profiling system at CARR

中子深度剖面分析(Neutron Depth Profiling,NDP)是一种高灵敏、高分辨测量材料近表面深度分布信息的无损检测技术,利用中国先进研究堆(China Advanced Research Reactor,CARR)冷中子束建立了一套中子深度剖面分析系统,该系统真空度优于其他NDP设备,可达到3.4×10-5 Pa。冷中子注量率高是其另一大优势,CARR在15 MW功率下运行时,用金活化法测得中子导管末端的中子注量率约为4.8×108cm-2?s-1。此外,该系统一次性可以测量6个样品,简单易行。通过测试美国国家标准与技术研究院(National Institute of Standards and Technology,NIST)标准物质SRM-2137评价CARR-NDP系统的性能,测量结果与参考值具有较好的一致性,验证了CARR-NDP系统的可行性。

[Background] Neutron depth profiling (NDP) is a non-destructive near-surface analysis technique and it is widely used in characterization of polymers, semiconductors, alloys, lithium ion battery materials, photoelectric materials and many other materials.[Purpose] This study aims is to develop NDP system to obtain the depth profiles of several crucial light nuclides (e.g., 6Li and 10B) in nearly any substrate.[Methods] Based on the cold neutron beam of China advanced research reactor (CARR), a NDP system was developed with vacuum reached 3.4×10^-5 Pa and neutron flux rate of 4.8×10^8cm^-2·s^-1.The standard reference material (SRM-2137) sample was used to test the performance of this NDP system. The measured α- particle spectrum was calculated by the inversion iterative algorithm to obtain the depth profiles of crucial elements.[Results] The experimental results show that the simulation results of SRM-2137 agree well with the experimental results. The maximum error is less than 4% at each layer of 5 nm thickness. The peak depth is very close to the reference value (188 nm). The depth accuracy is 0.53%.[Conclusions] Established CARR-NDP system and relevant experiments and data analysis techniques have been verified. The system will be further applied to investigating the lithium ion batteries, multilayer films and high-temperature alloys, etc.