Construction of ultra low concentration sample preparation and measurement system for Es-XAFS measurement in SPring-8

鈴木 伸一; 塩飽 秀啓; 小林 徹; 矢板 毅; 塚田 和明; 浅井 雅人; 豊嶋 厚史

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An element having an atomic number equal to or greater than neptunium is one of synthetic elements, and its abundance is governed by the half-life. In a general laboratory scale structural analyzer, it is difficult to clarify the hydration structure of these artificial elements, due to the problem of abundance and the radioactivity. At this time, we secured microgram amount of Einsteinium (Es). Es is the heaviest element in the periodic table that can acquire the microgram amount. Then, hydration structure study of Es was carried out at SPring-8 BL22XU. Approximately 0.2 microgram of 254 Es (half life 275 days) used for the experiment was irradiated and generated in 2017 in the HFIR reactor of Oak Ridge National Laboratory (ORNL). After that, it took about a half year to isolate 254Es in ORNL and it was delivered to JAEA 4 months later. Since other nuclides such as 253Es, 249Cf, 250Cf and 249Bk were also mixed in addition to 254Es at the time of acquisition, it is necessary to separate and purify and sample preparation for optimum condition for SPring-8 synchrotron radiation experiment. Therefore, 254Es was separated using a cation exchange separation method using alpha-HIB(alpha hydroxyl isobutyric acid). Furthermore, in order to remove alpha-HIB, an unnecessary complexing agent for SPring-8 experiments, hydrochloric acid-based cation exchange separation was carried out. The purified sample was dissolved in 50 macro liter of 0.1 N perchloric acid, sealed in a plastic container, and used as a synchrotron radiation experiment sample. The hydration structure elucidation experiment was measured by fluorescence method using 19 element semiconductor detector. In ultra-low concentration XAFS measurement, it is important to remove scattered rays from various materials around the measurement system. For this reason, BCLA: Bent Crystal Laue Analyzer which uses a curved Si crystal for spectroscopy in a Laue type arrangement was used as a spectroscopic crystal.