ABSTRACT
For the U-Th series radionuclides investigation in natural freshwater, a simple, fast, and not laboratory intensive method which consists of evaporating the water samples to dryness in the presence of carriers is presented. The small volume of the residue (1-2 cm3) leads to a good efficiency for gamma counting and limits the self-absorption effect for the low energy gamma rays (less than 200 keV). The best efficiency is obtained with a well-type Ge detector. To determine the evaporation yields a river with a common uranium content, the Seine river (France), was selected. By using internal spikes and more conventional techniques of investigation, we demonstrate that the evaporation is quantitative for U, Th, Ra, Pb, and Be. The residue of a 3 L, standard superficial freshwater, evaporated sample was analyzed in a high efficiency, low background Ge detector, which leads to a sufficient precision for most environmental studies. The method has been applied to rain, river, and lake waters to study the impact of disused uranium mine water inputs on the 238U, 228-234Th, 226-228Ra, 210Pb, and 7Be river and lake contents in the U mining area of Limoges (France).
Subject(s)
Environmental Monitoring/methods , Water Pollutants, Radioactive/analysis , Rain , Reproducibility of Results , Sensitivity and Specificity , Spectrometry, Gamma/methods , Water SupplyABSTRACT
The periodic domain inversion by direct electron-beam (EB) bombardment on Ti:LiNbO(3) is presented. Gratings with a 6.6-mum period are achieved. The inverted patterns are observed after chemical etching by use of a scanning electron microscope, and they exhibit a high resolution, as expected. Next, the influence of the EB parameters on the inversion phenomenon is developed for both LiNbO(3) and Ti:LiNbO(3). In this way we can provide an explanation of the phenomenon of domain inversion with an EB, which is not completely understood. Finally, quasi-phase-matched second-harmonic generation is presented in bulk LiNbO(3) by use of a Nd:YAG laser light. These experiments allowed us to achieve the characteristics of the inverted domains along the crystal in particular.
ABSTRACT
Optical guides are realized by ion irradiation in three polymers: polycarbonate, HIRI, and CR39. Optical properties (index variation, loss) are compared. CR39 waveguides present the best performances (with losses as low as 1 dB/cm); the influence of a curing parameter (initiator concentration), which is directly related to CR39 density and refractive index, is studied.
