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Posted: Nov 11, 2015
Made to order: Researchers discover a new form of crystalline matter
(Nanowerk News) Dust is everywhere: under the bed, on the stairs and even inside of plasmas. A team of researchers from Auburn University, the University of Iowa and the University of California, San Diego, using the new Magnetized Dusty Plasma Experiment (MDPX), the first U.S. experiment of its kind, recently discovered a new form of crystalline-like matter in strongly magnetized dusty plasma.
A feature of dusty plasmas is that under the proper conditions, usually at higher gas pressures, the dust particles can form self-organized, hexagonal structures--a configuration known as a "plasma crystal."
The striking aspect of the newly discovered crystal structures is that the lattice (spacing between crystal particles) properties can be imposed arbitrarily by an external grid/mesh structure (Figure 1). These new made-to-order crystals can have any geometric pattern, making them distinct from the crystal lattices of ordinary solids and traditional plasma crystals, which are self-organized structures not imposed by external boundary conditions.
[Left] Typical plasma crystal with a self-ordered, hexagonal arrangement of dust particles indicated by the bright white spots. [Middle] Made to order square pattern formed in an imposed dust crystalline-like structure. [Right] A typical dusty plasma illuminated by a green laser in the MDPX experiment at Auburn University. (Image: Max Planck Institute)
In space, scientists observe large dust structures in star-forming regions such as planetary nebula. Small dust grains--the thickness of human hair or smaller--form amazing structures such as Saturn's rings and the long tails of comets. Most of these naturally-occurring dusty plasma systems have a very complex interaction between plasma, magnetic fields and these tiny, charged grains of dust.
On the Earth, this same mixture of plasma, magnetic fields and charged dust grains, is often present in many industrial and research plasmas from semiconductor manufacturing to fusion experiments. In some cases, the dust is considered to be a source of contamination that needs to be controlled and safely removed from the plasma. But, if the properties of smaller (nanometer-scale) particles can be controlled and manipulated, they could prove to be an important tool in the future of plasma manufacturing.
Ongoing studies on the MDPX show the ability to control the shape of these ordered structures and where they are suspended in the plasma (Figure 2). In the future, this discovery could lead to new approaches to trapping and controlling micro-particles in plasma and further efforts in designing their properties for both fundamental physics investigations and possible processing and industrial applications.
Abstracts: JP12.00034 Analysis of particle trajectories in a simulated, magnetized dusty plasma in a radially-increasing electric field
NI2.00001 Summary of initial results from the Magnetized Dusty Plasma Experiment (MDPX) device
UP12.00057 A Single Particle Deflection Experiment for MDPX
UP12.00059 Probe induced voids at high magnetic field
UP12.00060 Imposed, ordered dust structures and other plasma features in a strongly magnetized plasma
Sessions Session JP12: Poster Session IV (Education and Outreach; Undergraduate/High School Research; DIII-D I, Diagnostics and Simulation Methods; Low Temperature Plasmas, Breakdown, Thrusters, and Sheaths). 2:00 PM-5:00 PM, Tuesday, November 17, 2015. Room: Exhibit Hall A
Session NI2: Waves and Instabilities. 9:30 AM-12:30 AM, Wednesday, November 18, 2015. Room: Chatham Ballroom C
Session UP12: Poster Session VIII (Pinches, Diagnostics, Codes and Modeling, One Component, Laser-Plasma Ions, Strongly Coupled and Dusty Plasmas). 2:00 PM-5:00 PM, Thursday, November 19, 2015. Room: Exhibit Hall A