High-pass mass filter

Riciputi LR (1996) A comparison of extreme energy filtering and high mass resolution techniques for the measurement of " S/ S ratios by ion microprobe. Rapid CommunMass Spec 10 282-286 Rona PA, Scott SD (1993) A special issue on sea-floor hydrothemal mineralization new perspectives. EconGeol 88 1935-1976... 

Neder H, Heusser G, Laubenstein M (2000) Low-level y-ray germanium-spectrometer to measure veiy low primordial radionuclide concentrations. ApplRadiat Isot 53 191-195 Palacz ZA, Freedman PA, Walder AJ (1992) Thorium isotope ratio measurements at high abundance sensitivity using a VG 54-30, an energy-filtered thermal ionization mass spectrometer. Chem Geol 101 157-165... 

There has been significant progress made recently in the fabrication of FO membranes. While these were not specifically tested for PRO operation (e.g. permeation rates under pressurized conditions), their estimated potential performance may be calculated based on the experimentally determined characteristics, namely, the water and salt permeabilities of the filtering layer and the mass transfer resistance of the support to diffusive transport. Membrane permeability is expressed in m/s-Pa and measures the water volume flow rate permeated across a membrane area unit under a 1 Pa osmotic pressure difference between the membrane sides. High values of water permeability denote the membrane capability of avoiding resistance to water flux. 

The poorer detection limits and sensitivity primarily arise from the low transmission of these mass filters. The transmission of these filters is also dependent on the secondary ion mjq ratio when set at constant mass resolution mode (the desired mode in SIMS), i.e. this decreases as the miq ratio increases. This poorer detection limits and sensitivity can, however, be partially compensated for using high primary ion currents (up to 10 pA can be used). Likewise, extraction fields of several hundred volts can be applied to capture a greater portion of the secondary ions produced, but only if they are subsequently decelerated before entering the Quadrapole mass filter region. 

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