Long-Range Particle Interactions and Collective Phenomena in Plasma Crystals
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Introduction
- Plasma crystals are a newly discovered phenomenon (Physical Review Letters, 1994) whereby large particles in an electrical plasma self-assemble into orderly arrangements due to collective interactions.
- The macroscopic size of the crystal offers a unique vehicle to:
- investigate the fundamental principles underlying long-range multi-particle interactions
- investigate collective phenomena in macro-crystals
- probe crystal structure and dynamics
- Recent literature has begun to document basic phenomena such as influence of discharge geometry and characteristic wave propagation, mach cone models, and experimental measurements of interaction potential effects due to gravity.
- Funded by Division of Material Sciences, Office of Science, US DOE, and Sandia National Laboratories.
Very regular 2D crystals with noticeable radial compression are produced in the parabolic well. For this crystal, 8.3 µm diameter Melamine spheres are suspended in a 100 mTorr, 1.8 W Argon plasma above a 0.5m radius of curvature lower electrode. The crystal contains 1155 particles and is 21.8mm in diameter.
Research Objectives
Our research objectives address fundamental issues. We are focusing our efforts on those areas where we have unique strengths, novel diagnostics, and/or first-principle models.
- Investigating inter particle forces and long range interaction mechanisms while asking:
- What really holds the arrangement together?
- Attractive forces?
- Can we identify and manipulate the forces?
- Identifying the crystal dynamic response, stability criterion, "defect" propagation
- Identifying novel crystal materials (perhaps magnetic dipoles)
- Developing new diagnostic techniques, particle mapping methodologies, statistics, and novel techniques to measure the electric fields between the particles (all under consideration as are methods to characterize the surface charge)
- Addressing concerns, such as, step changes in the plasma Debye length by electron heating
- Combining experiments and models to benchmark first-principle models and to describe the charged particle interaction potentials.
Point of Contact: Greg Hebner