Measurement of trace uranium isotopes using a porous ion emitter

The extent to which thermal ionization mass spectrometry (TIMS) can measure trace quantities of 233U and 236U in the presence of a huge excess of natural uranium is evaluated. This is an important nuclear non-proliferation measurement. Four ion production methods were evaluated with three mass spectrometer combinations. The most favorable combinations are not limited by abundance sensitivity; rather, the limitations are the ability to generate a uranium ion beam of sufficient intensity to obtain the required number of counts on the minor isotopes in relationship to detector background. The most favorable situations can measure isotope ratios in the range of 1 × 10−10 if sufficient sample intensity is available. These are the triple sector mass spectrometer with porous ion emitters (PIE) and the single sector mass spectrometer with energy filtering.

A systematical study of the performance of porous ion emitters, resin beads, and double filaments for TIMS analysis of trace uranium isotopes..Figure optionsDownload high-quality image (39 K)Download as PowerPoint slideResearch highlights▶ Trace U measurement is limited by signal-to-noise ratios, not abundance sensitivity. ▶ A sample generating nano amperes signal a triple sector instrument with a PIE will produce the best data. ▶ For a 1 μg sample, approximately 20 fg of each trace U isotope can be detected.