A triple-sector mass spectrometer with high transmission efficiency and 10 −11 isotope-abundance sensitivity

Abstract

We have used standard commercial mass spectrometer components to construct a triple-sector mass spectrometer of unique ion-optical design that achieves exceptional isotope-abundance sensitivity and high ion transmission efficiency. The spectrometer has tandem 90° deflection magnets with off-normal boundaries to provide vertical focusing of the ion beam. The first magnet provides a focus in the horizontal plane of mass dispersion and renders the ion beam parallel in the vertical plane. The second magnet brings the beam to a stigmatic focus. This novel ion-optical design gives 100% ion transmission without the need for intermediate focusing lenses. It also prevnets ion scattering from the top and bottom of the flight tube, thereby increasing isotope-abundance sensitivity. Complete transmission of ions is maintained through a third-stage cylindrical electric sector that further improves abundance sensitivity. The uranium equivalent isotopeabundance sensitivity of the new mass spectrometer is 1×10 −11, a two-orders-of-magnitude improvement over similar instruments with normal magnet boundaries.