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Optically-Excited Waves in 3D Dusty Plasmas John Goree The University of Iowa.

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Presentation on theme: "Optically-Excited Waves in 3D Dusty Plasmas John Goree The University of Iowa."— Presentation transcript:

1 Optically-Excited Waves in 3D Dusty Plasmas John Goree The University of Iowa

2 plasma = electrons + ions What is a dusty plasma? Debye shielding small particle of solid matter becomes negatively charged absorbs electrons and ions

3 Solar system Rings of Saturn Comet tails Fundamental science Coulomb crystals Waves Manufacturing Particle contamination (Si wafer processing) Nanomaterial synthesis Who cares about dusty plasmas?

4 Forces Acting on a Particle Coulomb QE Other forces: Gas drag Ion drag Thermophoresis Radiation Pressure Gravity mg

5 Electrostatic trapping of particles Equipotential contours electrode positive potential electrode With gravity, particles sediment to high-field region  2-D layer Without gravity, particles fill 3-D volume QE mg

6 polymer microspheres 8  m diameter Particles separation a  0.5 mm charge Q  - 10 4 e

7 Same: Coulomb repulsion Crystals Different: Dusty plasma has much lower damping rate  wave propagation is easier Comparison to Colloidal Suspensions

8 2D physics: Ground-based 3D physics: Flight Experiments described in this talk

9 triangular lattice with hexagonal symmetry 2D lattice Yukawa inter-particle potential

10 Two modes in a lattice

11 Dispersion relations in 2D triangular lattice Wang et al. PRL 2001  =0,

12 Setup

13 scanning mirror Scanning mirror Ar laser beam

14 Longitudinal wave 4mm k Laser incident here f = 1.8 Hz

15 Random particle motion No Laser! = compression + shear 4mm Nunomura et al. PRL 2002

16 Phonon spectrum & sinusoidally-excited waves Nunomura et al. PRL 2002

17 Mach cones

18 Mach cone angle C = U Sin   U

19 Lateral wake Transverse Wake Ship’s wake

20 water  air Wake pattern is determined by dispersion relation Mach cone Lateral & transverse wakes Has both features: Mach Cone Lateral & transverse wakes plasma crystal

21 Mach cone excitation V/C L = 1.17

22 Mach cone + lateral wakes Nosenko et al. PRL 2002

23 3D physics Microgravity

24 Predecessor microgravity experiments 1996-1998 Sounding rockets Morfill et al., PRL 1999 2001 – 2002 ISS - PKE

25 PKE vacuum chamber Cameras for imaging particles Laser sheets for illuminating particles

26 imaging cameras cw Nd-YAG laser (manipulation) galvanometer scanning mirror diode laser (for imaging) shown in a mid-deck locker:plasma chamber & optics not shown: gas/vacuum, power, data Flight hardware concept for optically-excited waves in 3D dusty plasmas

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