PKE-Nefedov — Complex plasma research on the international space station

Complex plasma research is a new and rapidly developing field, with investigations under gravity and microgravity conditions. The complex plasma consists of a common plasma — with electrons, ions and neutrals — and an additional component of small solid particles typically in the range of micrometers. This heavy component in the plasma makes it necessary to perform experiments under microgravity conditions although it is possible to levitate the particles in the laboratory as well. The microparticles in the plasma are charged through the absorption of free electrons and ions to thousands of elementary charges. On Earth, the particles can be levitated in a strong electric field. But this induces stresses to the particle cloud which can only be eliminated under microgravity conditions. It also implies that under gravity conditions only a small part of the parameter phase space of complex plasmas can be investigated. Therefore, to complete the research on complex plasmas, investigations under microgravity conditions are mandatory. This paper overviews the research on complex plasmas on the International Space Station ISS achieved with the first long-term experiment, PKE-Nefedov, used for this research.