Recent Results from the Plasmakristall-4 (PK-4) Microgravity Complex Plasma Laboratory

Abstract

Plasmakristall-4 (PK-4) is a Joint European-Russian microgravity complex plasma facility on the International Space Station [1]. In PK-4, the experiments are performed in a polarity-switched (with the frequency of hundreds Hz) dc discharge ignited between two electrodes in an elongated glass tube. Under microgravity conditions, plastic microspheres injected into this plasma form three-dimensional ordered structures. Miroparticles in the plasma are illuminated with a laser and observed by two videocameras. PK-4 offers many possibilities to manipulate the microparticle clouds. Many manipulation methods (modulation of the dc discharge, variation of the polarity-switching parameters, etc.) are plasma-mediated. Unlike those, manipulation laser allows to exert a radiation pressure force directly on the microparticles without influencing the background plasma. Also, several plasma diagnostic instruments are included into the system: e.g., glow observation camera and spectrometer. PK-4 was commissioned in June, 2015. Since then four experimental campaigns were performed with it. In this paper, the results obtained on PK-4 will be overviewed. Such topics, as microparticle charge and ion drag measurements, electrorheology, shear flows will be discussed. References [1] M.Y. Pustylnik et.al., Rev. Sci. Instrum. 87, 093505 (2016