Abstract: An improved rotating electric field ion mass spectrometer (REFIMS) provides for a smooth transition of the input ion beam from zero rotation to the desired level of field rotation. The REFIMS grid shape is changed from a fixed-diameter tunnel to that of a horn. The horn shape has a flare end with a larger entrance width that reduces the grid electric field strength to near zero and causes no abrupt deflection of the beam at the entrance, and tapers along the longitudinal z axis to a narrower width so that the field strength applied to the beam increases gradually until the correct field strength is obtained at its exit end for the desired rotation of the beam. Preferably, the horn shape in cross-section is hyperbolic, and the increase in field strength is approximately linear with distance along the z axis. The horn shaped device can provide a 2D spectral readout in which the ions are imaged on the target plane at radial positions increasing linearly with decreasing atomic mass units (amu).

Abstract: A membrane-introduction mass spectrometer (MIMS) device has a sample inlet assembly provided with a membrane held by an outer retaining ring across the entrance of a central passage, a porous metal frit backing the membrane, and a cylindrical support piece supporting the frit. In a preferred embodiment, the membrane is a 10-micron thickness layer of silicone evenly coated upon an inert polymer backing material. The porous frit is a titanium or steel sponge metal. The cylindrical support piece is made of titanium with small, drilled thru-holes to allow passage of gases and volatile organics into the mass spectrometer. The sample inlet assembly includes a high-pressure temperature probe for sensing fluid temperature to correct for temperature variations in membrane diffusion rates. The sample inlet assembly is provided as a front end to an underwater sampling probe.