State-of-the-art mass spectrometer system for determination of uranium and plutonium isotopic distributions in process samples

A Finnigan MAT 261 automated thermal ionization mass spectrometer system was purchased by the Savannah River Plant. The MAT 261 is a highly precise, fully automated instrument. Many features make this instrument the state-of-the-art technology in precision isotopic composition measurements. A unique feature of the MAT 261 is the ion detection system which permits measurement of the three uranium or plutonium masses simultaneously. All Faraday cup measuring channels are of the same design and each is equipped with a dedicated amplifier. Each amplifier is connected to a linear voltage/frequency measuring system for ion current integration. These outputs are fed into a Hewlett-Packard 9845T desk-top computer. The computer, and the Finnigan developed software package, control filament heating cycles, sample preconditioning, ion beam focusing, carrousel rotation, mass selection, and data collection and reduction. Precision, accuracy, and linearity were determined under normal laboratory conditions using a NBS uranium suite of standards. These results along with other development in setting up the instrument are presented