Sterling Smith's Research Home Page

Curriculum Vitae

Publications

I am currently working with Dr. Steve Jardin. The topic of our research is the resistive wall mode in a cylindrical geometry. The resistive wall mode occurs when a free boundary kink mode in a plasma would be stabilized by a perfectly conducting wall at the same radial location, but the finite resistivity of the wall allows the perturbed magnetic field to penetrate the wall on a timescale of the resistive wall time, σbd, where σ is the conductivity of the wall, b is the wall location, and d is the wall thickness. It is predicted theoretically and observed experimentally that the RWM can be stabilized with sufficient flow. This is shown in the following plot

Wavelets

I spent the summer of 2006 working with Dr. Cynthia Phillips as the practicum for my Department of Energy Fusion Energy Sciences Graduate Fellowship. Most wave modelling codes currently use a Fourier expansion, since the dielectric tensors have been calculated in this basis. However, the Fourier expansion has no localization, such as is present in mode conversion in Tokamaks. The Gabor wavelet is a basis similar to the Fourier expansion: it is simply a Gaussian envelope on a Fourier expansion. It was my project to investigate the behavior of ordinary differential equations, including a mode conversion equation, solved with the Gabor expansion. I also looked at ways of utilizing the localization of the Gabor packets to preemptively eliminate the shortest wave length modes in those regions of space where none should exist. The next step for this project is to find a good 2-D or 3-D test problem to find out if the the Gabor packets perform as well as extrapolated from the 1-D case.

Grad Lab

During my semester in the plasma physics grad lab course, I explored 4 separate concepts concerning plasmas. Listed below are the reports which these explorations inspired.
1. Determination of Afterglow Decay Constants of a Pulsed Argon Glow Discharge Plasma
2. Paschen's Law in Air and Noble Gases

The following graphs were obtained by Undergraduates during the week of undergraduate plasma research through the REU or NSF(?).
signal.jpg spectrum.jpg volt_vs_freq.jpg

NSTX

My first year project was working with Dr. Jon Menard analyzing magnetics data from NSTX at the Princeton Plasma Physics Laboratory. I attended the 2005 Meeting of the APS DPP (Division of Plasma Physics of the American Physical Society) in Denver to present the results of this research. The abstract is here. An electronic copy of the poster is here.

Graphitic Amorphous Carbon

To probe the evolution of the nanoscale structure of an ubiquitous carbon-based material, I extended a novel computational method. The material of unknown nanoscale structure was graphitic amorphous carbon (g-C), a common coproduct found in the making of carbon nanotubes, buckyballs, artificial diamonds, and graphite. A better understanding of the structure of g-C could lead to the more efficient production of these technologically valuable materials. Toward this better understanding, I applied the Embedded Ring Approach (ERA) to the in-plane motions of g-C. The ERA is a vibrational model for analyzing the motions of atoms in planar materials based on a structural model that assumes constituent atoms are arranged in planar rings of 4 to 8 atoms. I specifically used the ERA to calculate the in-plane vibrational frequencies which are detectable by Raman spectroscopy. The Raman spectra of g-C samples annealed to different temperatures were experimentally obtained. By fitting the spectra with Guassian curves based on the ERA frequencies, the ring statistics were determined. In particular, room temperature g-C is composed of a mixture of 5,6, and 7 member rings, but as g-C is annealed to higher temperatures, an increase in its graphitic content is observed, as evidenced by an increase in the fraction of 6 member rings and in the sharpness of the peaks in the Raman spectra.

I presented a poster regarding this research at the Utah Undergraduate Research Day at the Capitol on January 22, 2004. Click here to see the brochure. (I am on pg. 36.) I also presented at the March Meeting of the American Physical Society in Montreal. Click here to see the abstract.

Other Home Pages

If you have any suggestions or questions, let me know.
spsmith@pppl.gov