Plasma Atomization of Strontium Chloride Powder by a Supersonic Plasma Jet and Measurement of Its Efficiency Using Diode Laser Absorption Spectroscopy

Direct elemental and isotope analyses of solid samples have attracted considerable interest due to their potential role in preventing serious accidents at nuclear facilities. We previously developed an analytical method for detecting radioactive isotopes, combining diode laser absorption spectroscopy with a supersonic plasma jet. Its basic performance, that is, the detection limit as well as the translational temperature upstream and downstream of the supersonic nozzle, was investigated using stable Xe isotopes. The developed apparatus could atomize a solid sample and reduce the translational temperature for isotope identification. For direct isotope analysis, translational temperature and atomization efficiency during powder feeding are remarkably important. In the present study, a novel approach for the atomization of Sr powder samples containing isotopes with highly radiotoxic radionuclides is described. We found that the temperature of Sr atoms in the supersonic plasma jet decreased to approximately 85 K, which is comparable with the slight isotope shift of ⁸⁸Sr-⁹⁰Sr due to the difference in mass number. Moreover, based on the measured atomic number density and flow velocity, the atomization efficiency was found to be 10.4 ± 1.8%. The results of this study and further improvements in the efficiency can lead to the development of powerful tools for the rapid analysis of solid samples, particularly those contaminated with highly radioactive species, without the necessity for complex chemical separation.