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Measurement of anthropogenic radionuclides in post-Fukushima Pacific seawater samples

Lutter G., Tzika F., Hult M., Aoyama M., Hamajima Y., Marissens G., Stroh H.

Nukleonika

2015

Vol. 60, No. 3, part 2

545--550

Following the accident at the Daiichi Fukushima nuclear power plant in 2011, a vast number of Pacific seawater samples from many locations far from Fukushima have been collected by Japanese investigators. Due to dilution, the activities of radionuclides from North Pacifi c seawater samples are very low, which calls for extraordinary measures when being measured. This study focuses on the metrological aspects of the gamma-ray spectrometry measurements performed on such samples in two underground laboratories; at HADES (by JRC- -IRMM in Belgium), and at Ogoya (by Kanazawa University in Japan). Due to many samples and long measurement times, all available HPGe detectors needed to be employed. In addition to single coaxial detectors, this involved multidetector systems and well detectors. Optimization of detection limits for different radionuclides and detectors was performed using Monte Carlo simulations.

Spectral ellipsometry of binary optic gratings

Pištora J., Yamaguchi T., Vlček J., Mistrik J., Horie M., Smatko V., Kováčová E., Postava K., Aoyama M.

Optica Applicata

2003

Vol. 33, nr 2-3

251-262

The coupled wave method (CWM) has been applied to the description of electromagnetic wave propagation in binary optic gratings. The electromagnetic field and the permittivity profile are expanded into two-fold Fourier series. The reflection coefficients of 2D periodical structures have been specified and the ellipsometric angles of the shapes discussed have been computed. The theo-retical results are compared with experimental data obtained on SiO2 square dots on Si substrate. The measurements were performed using computer controlled four zone null ellipsometer in spectral range from 240 nm to 700 nm. The influence of SiO2 ultrathin oxidation layer and thickness of dots on spectral ellipsometric angles is also discussed