Absorption spectroscopy of uranium plasma for remote isotope analysis of next-generation nuclear fuel

Miyabe, Masabumi   ; Oba, Masaki ; Iimura, Hideki  ; Akaoka, Katsuaki ; Maruyama, Yoichiro; Oba, Hironori  ; Tampo, Motonobu; Wakaida, Ikuo  

A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm. The temporal evolution of the ablation plume was investigated in vacuum and helium environments. In vacuum, the flow velocity perpendicular to the sample surface was determined to be 2.7 km/s for neutral atoms and 4.0 km/s for singly charged atoms. From the evolution of the plume in helium we found that an observation time of 3-5 s and an observation height of about 2.5 mm are most suited for obtaining higher sensitivity. Observation times less than 3 s were unsuitable for precise isotope analysis since the spectral modifications arising from the Doppler splitting effect are different between the two uranium isotopes. Using the established conditions, we evaluated the calibration curve linearity, limit of detection, and precision for three samples having different abundances of U.