Quantification techniques of mass-separation and ion yield for the detection of radioactive isotopes

This research demonstrates two methods of quantifying ion yield efficiency using an inductively coupled plasma mass spectrometer. The mass spectrometer is used as a means of separation where individual decay mass-chains are isolated (i.e., implanted) onto a conductive substrate. Quantifying the ion yield of this recovery process is crucial to understanding the abundance of the separated isotope present in the unseparated starting sample. The first method measured the accumulated charge directly incident on the conductive substrate in real-time while the second method performed a full chemical analysis of the substrate after dissolution. Our previous results demonstrated and compared these quantification methods with a multi-element standard of stable isotopes. This research expands on previous results and utilizes the stable mass ion yield to quantify trace amounts of the (radioactive) isotope of interest present in the sample. The mass-separated radioactive isotopes were fission products produced from thermal neutron irradiation of a highly enriched 235U foil. Five peak-yield mass chains were targeted. The results indicate good correlation between the two methods of measuring the ion yield and imply that coupling this method with traditional radiometric counting can result in an accurate means of quantifying radioactive isotopes. The final results we report here are within 1-sigma of the published cumulative fission yields.