Hope College Physics Department
Research Experiences for Undergraduates
Summer 2013
Project Summary


Project Title: Microplasma Ignition
Student Name: Joseph Campbell
Student's Home Institution: Grand Valley State University
Research Advisor: Dr. Stephen Remillard
Source of Support:

This project was funded by the National Science Foundation grant number PHY/DMR-1004811, and the Hope College Division of Natural and Applied Sciences.

Many devices depend on an understanding of the microwave breakdown process. The pressure dependence of the breakdown threshold electric field for nitrogen gas in microgaps down to 12.7 µm had been measured using a foreshortened quarter wave resonator excited with microwave fields in the GHz range. Two different pressure regimes in these microgaps have been identified where the breakdown either happens outside for one or inside the microgap for the other. There is a sharp transition between these two pressure regimes, allowing the phenomenological function

to be fit separately in both regimes. The two key fit parameters are B, the collision frequency per torr, and m, the power law dependence of pressure. Spectroscopic measurements led to a physical description of the induced plasma. The first positive system of nitrogen gas was found to be suppressed in comparison to the second positive system in micro gaps. In contrast, in the transition gap range, from micro to macro gaps, at high pressure the first positive system was enhanced and the second positive system was suppressed producing a yellow plasma which is not typical of nitrogen gas.

Publications and Presentations:

"Collision and diffusion in microwave breakdown of nitrogen gas in and around microgaps," J.D. Campbell*, A. Bowman, III*, G.T. Lenters, and S.K. Remillard, AIP Advances, Vol. 4, no. 1, 017119, (2014).