Dust Mass Spectrometer (PUMA)

Description

This investigation (PUMA) was designed to estimate the mass and chemical composition of particles in the dust coma. A similar instrument will be flown on the Giotto spacecraft. The instrument was mounted parallel to the relative velocity vector and analyzed the chemical and isotopic composition of individual dust particles. Impact of a dust particle on the instrument's silver target area caused a plasma to be formed consisting of dust and target material, from which ions were extracted by a 1.5-kV electric field. The ions traveled through a time-of-flight tube (actually two tubes with an electrostatic reflector between, with total length of 1 m) where they were separated according to their mass before being recorded by an electron multiplier. The ion mass range was 1 to 100 u, with resolution M/(delta M) of 200. The instrument observed the spectra of the most common dust particles, which were expected to be in the size range 100 to 10,000 nm. The instrument was sensitive to dust particles in the mass range 3E-16 to 5E-10 g.