Laser spectroscopy for atoms and fine particles generated during laser cutting

Miyabe, Masabumi   ; Yamada, Tomonori; Shibata, Takuya  ; Ito, Chikara   ; Daido, Hiroyuki; Hasegawa, Shuichi*

It is expected that laser cutting process will be used in decommissioning for nuclear facilities, but there are concerns about environmental pollution due to the fume generated during laser cutting. To clarify the formation mechanism and characteristics of atoms and fine particles in the fume and to rapidly analyze the isotopic composition, we conducted atomic spectroscopy associated with laser ablation and an experiment to decompose the fine particles by optical fragmentation process. When diode laser was tuned to the resonance wavelength of Ca in ground state and the temporal variation of the transmittance was observed with an oscilloscope, the recovery of the transmittance due to the disappearance of the neutral atoms was observed within a few milliseconds after the ablation. After another 50 ms, when the fragmentation laser beam was irradiated to the plume composed of remaining fine particles, being careful not to hit the sample, pulse-like attenuation of the transmitted light due to atomic absorption was observed again. When ablation laser beam is blocked and only the fragmentation beam is irradiated, the attenuation o the transmittance disappear; thus it is confirmed that the signal is derived from the decomposed fine particles. This study suggests that the possibility of online analysis by fragmentation of fine particles generated during laser cutting.