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Laroussi's Research Finds Plasma Plume Is Actually Plasma Pellets

Old Dominion University electrical engineer Mounir Laroussi has garnered media attention internationally for his so-called plasma pencil that has been likened to a Star Wars light saber. But in his latest research paper, he admits that he now knows that his invention does not shoot out a saber-like jet of cold plasma, but rather operates like a rapid-fire machine gun spitting out cold plasma pellets.

To the naked eye, the plasma appears to come out of the hand-held plasma pencil in a continuous flow up to 2.5 inches long. But a camera with an exposure time of a few nanoseconds revealed that the jet was actually composed of tiny, donut shaped pellets that are fired out of the pencil and then dissipate in the ambient air after traveling an inch or two. Laroussi said by knowing more about the makeup of the plumes, he and his colleagues will be able to better control them.

Biological research begun earlier at ODU, and which is continuing, investigates uses of the cold plasma to kill harmful bacteria in the mouth, disinfect wounds and speed healing.

An article authored by Laroussi and his students, which was published earlier this year in Journal of Physics D: Applied Physics, lays out recent discoveries at ODU's Laser and Plasma Engineering Institute (LPEI) about fundamental aspects of cold plasma plumes. Laroussi is the director of the institute.

On Friday, Feb. 27, PhysOrg.com published a report on the research with the headline Scientists Control Plasma Bullets. "The article we published is stirring up quite a bit of interest," Laroussi said.

He told PhysOrg.com that his recent research seeks to understand the physics behind the formation and propagation of the cold plasma bullets. "There has been a lot of debate as to how these bullets propagate. So we hope that we have contributed some interesting ideas to this debate." The article can be found at http://www.physorg.com/news154951518.html.

Based on the donut shape of the plasma pellets, the researchers believe that they are surface waves that travel along the interface between the helium pumped by the pencil and ambient air. In addition, the researchers found that they could control the initiation time and distance of the plasma pellets by applying an external DC field.

Most people are familiar with the plasma that is used to light up fluorescent bulbs and television screens, but this supercharged gas is contained in a vacuum and would be too hot and difficult to manage in the regular atmosphere. Laroussi has been a pioneer in the generation and bioapplication of cold plasma that is cool enough to pass a finger through even though it packs enough wallop to kill bacteria.

The lead author of the article in Journal of Physics D: Applied Physics is Nicolas Mericam-Bourdet, an intern researcher at LPEI. Other authors are Asma Begum and Erdinc Karakas, who are ODU doctoral students working with Laroussi.

This article was posted on: February 27, 2009

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