A compact time‐of‐flight mass spectrometer for high‐flux cosmic dust analysis

Abstract

Time‐of‐flight mass spectrometers on spacecraft are the most direct method for determining chemical composition of cosmic dust grains. Miniaturization of these instruments presents many challenges. Larger space‐charge effects, greater deviations from the paraxial approximation, and various ion‐optical aberrations negatively affect mass resolution in small time‐of‐flight instruments. We report on the building and testing of an instrument design that may reduce these effects. In addition to a linear reflectron, ions pass through a ring aperture that transmits only those ions with transverse velocity components that fall within a specific range. This novel design focuses ions onto a detector with greatly reduced spherical aberration. Space‐charge effects and the effects of impact plate cratering and grid scatter are also reduced using this design. Controlled impacts of iron microparticles at several km/s demonstrate instrument performance. This instrument is suited for characterization of cosmic dust in regions of very high dust flux, such as a comet flyby, and it may also have practical laboratory or field applications.