The Sputtering of Dust Grains: Aspects of Experimental Observations

Dust grains are sputtered at every environment containing energetic ions (i.e., ions with energies of several kiloelectronvolts). In the laboratory, only the beam experiments would fulfil these conditions; however, in the space, ions of these energies can be found even in the solar wind. It was suggested that the sputtering is one of the most important destruction processes of micrometer-sized dust grains, and on the other hand, it would be a source of heavy species in the interplanetary medium. We simulate the space environment by trapping the dust grains in an electrodynamic quadrupole trap and by influencing them by the ion beam with a variable energy up to 5 keV. The grains are charged to high surface potentials, and thus, a strong electric field near the surface can affect the sputtering rate. The finite size and the small curvature radius of grains play an important role in the quantification of sputtering efficiency. We propose a simple sputtering model for spherical grains and compare its predictions with measurements. An interpretation of the preliminary results obtained on gold microspheres bombarded by argon ions indicates that not only the grain mass but also the grain shape is changing in the course of our experiment. We suggest that similar effects can occur in the space if the dust is exposed to collimated ion beams