Daisuke Akiyama

Beam homogenizer for hollow-fiber delivery system of excimer laser light

A beam homogenizer for a hollow-fiber-based, UV laser delivery system is proposed. A rectangular glass waveguide with an inner aluminum coating that has a 1-mm square cross section is attached at the output end of the circular-core hollow fiber with a 1-mm inner diameter. The rectangular waveguide generates a number of higher-order modes and results in a uniform top-hat profile. The configuration of the waveguide is designed by a ray-tracing technique so that both the low transmission loss and the high uniformity in the output beam are obtained. The fabricated waveguide shows a low loss of 0.4 dB, and the intensity variation coefficient is 7%. The output beam from the rectangular waveguide is expanded by a lens to the size larger than 10-mm square. It is also shown that the profile does not change with the bending condition.

Characterization and thermodynamic study of humic acid in deep groundwater at Horonobe, Hokkaido, Japan

ABSTRACT In this study, humic substances (humic acid and fulvic acid) were isolated from deep groundwater at −350 m depth of Horonobe, Hokkaido, Japan to compare the characteristic property and reaction mechanism with generic humic acid isolated from surface soils. The size distributions of Horonobe humic substances were analyzed by size exclusion chromatography, flow-field flow fractionation, and total organic carbon measurement with ultrafiltration. All of them indicated small molecular weight and particle size of Horonobe humic acid in comparison with generic humic acids. Additionally, the simple protonation behavior of Horonobe humic substances similar to benzoic acid and/or phenol was revealed by thermodynamic quantities obtained by potentiometry and calorimetry. Consequently, molecular size and the reaction mechanism of Horonobe humic substances are different from generic humic acids, due to the characteristic origin.