In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.
Previously, we developed a simple semi-theoretical calibration procedure for a pulsed photoacoustic set-up. Also, we analysed the simplest, idealized case: top hat spatial profile of the laser beam and an exponential decay of excitation energy. The spatial profile of the laser beam is usually considered to be top hat or Gaussian in the photoacoustic measurements. In reality, there are always small discrepancies. Also, in these measurements the excitation energy decay is usually considered to be an exponential one. This assumption is commonly valid. Still, a non-exponential decay can exist as well. In this paper, we have examined the influence of these discrepancies on the measurement of the vibrational-to-translational relaxation time, as well as on the calibration of the photoacoustic set-up. We have theoretically examined gas mixtures in the case of pulsed excitation (multiphoton regime). Then, we have verified theoretical conclusions in one experimental example. It has been shown that the non-ideal profile and excitation energy decay can significantly influence the measurement of the vibrational-to-translational relaxation time. Also, it has been shown that they do not significantly influence the calibration of the photoacoustic set-up.
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