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Dr. Alexandros Gerakis and Dr. Kentaro Hara
Drs. Alexandros Gerakis and Kentaro Hara | Image: Igor Kraguljac

With a $300,000 grant from the National Science Foundation, a team of researchers at Texas A&M University is diving deep into the physics of plasma to question the fundamental theory of local thermodynamic equilibrium (LTE) in arc discharges.

Plasma, often called the fourth state of matter, is an ionized gas that is present in almost every aspect of everyday life. While an electric arc discharge is one of the most basic plasma phenomena used in industry and observed in nature, few things are fully understood about it. Because of this, scientists usually use assumptions to explain the behavior of plasma, including that of LTE.

An arc discharge is the easiest way to generate plasma, a method used for over 200 years. One way an arc discharge can be created is by connecting two electrodes with two respective poles of a power supply placed a distance apart. By increasing the voltage between them, once breakdown of surrounding gas is reached, an arc discharge is created, accompanied by the emission of light, much like lightning and spark plugs.

LTE states that all temperatures (translational, vibrational, rotational and electronic) of the particles involved in the arc discharge have the exact same value. The validity of this assumption has never been fully studied until now, mainly due to lack of the experimental capabilities.  

Dr. Alexandros Gerakis and Dr. Ken Hara, assistant professors in the Department of Aerospace Engineering, will approach the problem from a theoretical/simulation side as well as an experimental one. Hara will develop a simulation model to explain what is going on in the plasma, while Gerakis will use an innovative laser diagnostic tool called coherent Rayleigh-Brillouin scattering (CRBS), along with optical emission spectroscopy, to experimentally study the arc discharge. Texas A&M is a world leading institution with active research on CRBS and its applications through Gerakis’ Optical Probing and Manipulation lab.

The theoretical and experimental observations will be then compared against each other to gain complete understanding of the problem at hand. Successful outcome of this research will help gain a better understanding of the plasma operation and subsequent applicability. Understanding the nonequilibrium and equilibrium nature of the atmospheric arc discharge will provide better predictive modeling capabilities, which could eventually be used to improve the controllability and selectivity of chemical processes, such as for nanomaterial synthesis.

In conjunction with the research, Gerakis and Hara will develop a DC plasma source for educational outreach activities in conjunction with the Science Education Program at Princeton Plasma Physics Laboratory. They hope to use this in participation with local science festivals to provide K-12 students hands-on learning experiences in plasma physics.