Determination of the isotopic composition of trace amounts of actinides in environmental micro-particles by Resonance Ionisation Mass Spectroscopy (RIMS) of sputtered neutrals (SN)

应发展和应用共振电离质谱（RIMS）来研究微量锕系元素，尤其是铀和钚在微米级粒子中的同位素组成。这类粒子在污染区域的风险评估、核法医分析以及国际原子能机构和欧洲原子能机构的保障计划中具有很高的意义。它们通常由氧化铀基质组成，其中含有微量钚和镅。锕系元素同位素组成的测定用于推断粒子的起源、年龄和历史。次级离子质谱法（SIMS）是分析小颗粒的标准技术，它使用离子枪溅射与次级离子的质量选择性检测相结合。它受到等压干扰（238U/238Pu, 241Am/241Pu）。将RIMS与离子枪溅射相结合，将溅射后的中性离子离子化，而不是使用二次离子，有望成为克服等压干扰问题的一种优雅的工具。除了使用多步共振电离时具有极高的元素选择性外，由于离子枪溅射产生的主要是中性粒子，因此可以预期效率的提高。拟议的装置需要升级美因茨大学<s:1>化学研究所（Institut r Kernchemie）的RIMS系统，配备一个离子枪，该离子枪具有小点尺寸，用于从微米大小的颗粒中溅射材料，并配备一个新的样品台，允许处理颗粒样品。用于共振电离的激光系统和用于记录产生的离子的飞行时间质谱仪已经存在。在之前的一个项目中进行了可行性研究。

Resonance ionisation mass spectroscopy (RIMS) should be developed and applied for the investigation of the isotopic composition of trace amounts of actinides, most important uranium and plutonium, in micron-size particles. Such particles are of high interest in the context of a risk assessment of contaminated areas, nuclear forensic analyses as well as IAEA and Euratom safeguards programs. They usually consist of a uranium oxide matrix, which contains plutonium and americium traces. The determination of the actinide isotopic composition is used to deduce the origin, age and history of the particles. The standard technique for the analysis of small particles, secondary ion mass spectrometry (SIMS), uses ion gun sputtering in combination with mass-selective detection of the secondary ions. It suffers from isobaric interferences (238U/238Pu, 241Am/241Pu). The use of RIMS in combination with ion gun sputtering, post-ionising the sputtered neutrals rather than using the secondary ions, promises to be an elegant tool to overcome the problem of isobaric interference. In addition to extremely high element selectivity when using multi-step resonant ionisation, an increase in efficiency can be expected as ion gun sputtering produces predominantly neutral particles. The proposed set-up requires upgrading the RIMS system the Institut für Kernchemie at the University of Mainz with an ion gun that has a small spot size for sputtering off material from micron-size particles and a new sample stage that allows the handling of particulate samples. A laser system for resonant ionisation and a time-of-flight mass spectrometer for the registration of the created ions already exist. A feasibility study was performed in a previous project.