The Helix SFT is a 120° magnetic sector mass spectrometer with a 35 cm radius of curvature. It is equipped with a single Faraday cup and an ion-counting electron multiplier with an ESA. The large dispersion of this instrument provides very high abundance sensitivity, better than 1 ppb from mass 4 at mass 3, and the split flight tube allows simultaneous collection of helium-4 on the Faraday cup and helium-3 on the multiplier. We primarily use this instrument to measure low abundance helium-3 and neon isotope ratios. It is equipped with diffusion cells and a laser heating chamber, as well as to a conventional double vacuum resistance furnace.