Experiment zur Bildung und Untersuchung eines Plasmakristalls im schwerelosen Raum Schlussbericht

In the period of the grant the worldwide first experiments on complex plasmas under microgravity conditions on two parabolic flight campaigns and two sounding rockets has been performed. Thus, pioneer work had to be performed, because earlier simplified, theoretical considerations of these circumstances had been known, only. If the gravity drops out, or (more exact) if experiments are performed under accelleration between 10"-"2-10"-"4 g other much weaker forces than in the lab dominate the microparticles. The bulk forces which act on the microparticles are ion drag, electrostatic, thermophoretic, density gradients and neutral gas friction forces. In the above mentioned experiments it was possible to study these weak forces directly for the first time. Due to the force equilibrium the particles move out of the center of the plasma, leaving a dust free void in the center. The size of the microparticle-free zone can be changed by changing the particle size or the rf-power. The structure of the observed particle could shows crystalline as well as fluid characteristics. At the edges of the particle cloud toroidal convection can be found. The size and velocity of this convection depends on the plasma parameters, too. At very low plasma powers instabilities of the particle cloud occur, which show cyclic contraction of the cloud towards the center and away from it. (orig.)SIGLEAvailable from TIB Hannover: F99B1244+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany); DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Bonn (Germany)DEGerman