Laboratory Study of Ion Expansion from Hypervelocity Dust Impacts

In a laboratory study we investigate the angular distribution of ions expanding from hypervelocity dust impacts. Electric field antennas operated on many spacecrafts are often used for detecting dust impacts for characterizing interplanetary and interstellar dust populations within the solar system. The recorded waveforms from dust impact events are diverse, as their shape depends on the mode of operation (dipole vs. monopole), impact location with respect to the antennas, spacecraft potential, or the properties of the dust particles. A unique experimental setup is developed using delay line detector (DLD) for measuring the properties of the ion cloud expanding from the impact generated plasma cloud. Micron and sub-micron sized dust particles are accelerated to velocities > 1 km/s using the dust accelerator operated at the University of Colorado. The accelerated particles impact a tungsten target plate after which the generated ion cloud expends freely in a field-free region. After the expansion the ions are detected using the DLD that provides the location of their detection, which in turn is used for calculating the angular distribution of ions with respect to target normal. The preliminary results indicate that the impact-generated ions expand in the form of a narrow cone and the cone angle increases with increasing impact speed.