Dust Interaction with Charged Particles in Laboratory

Dust in space is subject to various interactions of photons and charged particles. Whereas photoemission is rather well understood, the charging of dust grains due to the interaction with charged particles has many variations and was not study in detail so far. We report the first laboratory experiment dealing with some less pronounced and often neglected secondary processes, e.g., secondary electron emissions due to ion, electron or positron impacts. We employed a quadrupole trap to store a single micrometer-sized silicate dust grain and measure variations of its charge with an accuracy of one elementary charge. The determined yields of secondary processes exhibit surprisingly large values. We discuss the experimental results and formulate possible consequences for space dust charging.