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

应发展并应用共振电离质谱仪(RIMS)来研究微米级颗粒中痕量吖系元素的同位素组成，其中最重要的是铀和钚。在对受污染地区进行风险评估、核法医分析以及国际原子能机构和欧洲原子能机构保障监督计划的背景下，这些粒子引起了人们的高度关注。它们通常由铀氧化物基质组成，其中含有微量的钚和汞。通过测定榄系元素的同位素组成来推断这些粒子的起源、年龄和历史。分析小颗粒的标准技术，二次离子质谱仪(SIMS)，使用离子枪溅射和二次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，对溅射的中性粒子进行离子后电离，而不是使用二次离子，有望成为克服等压干扰问题的一种巧妙工具。除了使用多级共振电离时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，效率有望提高。拟议的设置需要升级RIMS系统，美因茨大学的Institut für KernChemie使用一种离子枪，这种离子枪具有较小的光斑尺寸，可以从微米尺寸的颗粒中溅射出材料，并需要一个新的样品台来处理颗粒样品。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。在以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.