Development of an advanced Dust Telescope

A dust telescope is a combination of a dust trajectory sensor together with an analyzer for the chemical composition of dust particles in space. Dust particles' trajectories are determined by the measurement of the electric signals that are induced when a charged grain flies through a position sensitive electrode system. The objective of the trajectory sensor is to measure dust charges in the range 10^-16 to 10^-13 C and dust speeds in the range 6 to 100 km/s. The trajectory sensor has four sensor planes consisting of about 30 wire electrodes each. Two adjacent planes have orthogonal wire direction. The distance between planes is about 40 mm and the distance between electrodes in one plane is about 20 mm. The expected noise on each electrode is about 3 \cdot 10^-17 C. The signal on each electrode is sampled at 25 MHz rate. Simulated charge signals have been analyzed and dust charges and trajectories at a signal-to-noise ratio of 3 have been recovered. First tests with a laboratory set-up have been performed. The dust chemical analyzers will have a sufficient mass resolution in order to resolve ions with atomic mass number up to 100. The annular impact area of the mass analyzer will be 0.1 m². We have constructed a numerical (SIMION) model of the mass spectrometer consisting of the target area with an acceleration grid and the single-stage reflectron consisting of two grids and the central ion detector. Ions of varying starting positions at the target, emission angles 0 to 90 degrees and energies 0 to 50 eV are flown through the spectrometer. A first result is that ions with different perpendicular (to the target normal) energies will arrive at the ion detector at different radial positions, with zero perpendicular energy in the center. A mass resolution of M/ΔM > 150 can be obtained for impacts onto the annular target between 120 and 240 mm from the center. An Ion Detector of 110 mm radius is necessary to collect all generated ions. Acknowledgements: This research is supported by NASA grant NAG5-11782 and by DLR grant 50OO0201.