Total evaporation measurements: experience with multi-collector instruments and a thermal ionization quadrupole mass spectrometer

Abstract Results and experience are presented for a method of “fractionation free” measurements in thermal ionization mass spectrometery. The method can be used not only on multi-collector mass spectrometers, where the isotopes of interest can be measured simultaneously, but also on a thermal ionization quadrupole mass spectrometer using a special scanning and heating sequence. The total evaporation method strongly decreases the errors due to uncorrected fractionation when the amount of sample loaded on the filament varies widely. Resin beads containing only 1 ng of U and/or Pu can also be analyzed. The performance is demonstrated on uranium and plutonium samples.