The Department of Electrical and Computer Engineering at Boise State Welcomes you to join us for a free public seminar on December 4 at 10:30 AM in the Ruch Engineering Building, room 103.
This week's featured speaker is Allen L. Garner, Associate Professor of Nuclear Engineering at Purdue University
Explore Current Research on the Theoretical and Experimental Unification of Electron Emission Mechanisms
The reduction in the size of vacuum electronics, such as carbon nanotube field emitters, and the growing popularity of microplasmas for numerous applications encourages exploration of the impact of nanoscale behavior on electron emission and gas breakdown. While Townsend avalanche drives conventional gas breakdown, field emission drives gas breakdown at microscale. At smaller gap distances, electron emission transitions to space-charge limited and, ultimately, quantum driven. This talk summarizes the use of theory and experiment to unify these different emission mechanisms in a universal (true for any gas) theory.We first apply a matched asymptotic analysis to unify field emission with Townsend avalanche and discuss extensions for comparing to experiment and quantifying the potential impact of geometry, surface roughness, and space charge on gas breakdown by theoretically assessing the transition between various electron emission mechanisms. Specifically, we derive an analytic condition for a “triple-point” at the intersection of the Child-Langmuir and Mott-Gurney laws, which predict the vacuum and collisional space-charge limits, respectively, and the Fowler-Nordheim law for field emission and demonstrate the impact of external resistance on these transitions. We then develop a single set of scaling parameters to unify Paschen’s law, which is valid for gaps above microscale, to Schrödinger’s equation, which is valid down to tens of nanometers. Since many of these theories assume planar geometries, we further use variational calculus to derive a coordinate-system invariant representation of space-charge limited emission and derive exact, analytic equations for spherical and cylindrical geometries. These efforts provide a framework to examine electron emission for numerous gap sizes, pressures, and geometries.
Next, we experimentally show that surface roughness does not alter DC gas breakdown voltage; however, breakdown at small gap distances creates craters that change breakdown voltage by altering the effective gap distance. We will also describe the construction of electrodes with various aspect ratios to analytically determine the impact of electrode geometry and field enhancement on gas breakdown voltage as a function of pressure, gap distance, and gas.
SPEAKER BIO | Dr. Allen L. Garner received his BS degree with high honors in nuclear engineering from the University of Illinois, Urbana-Champaign, in 1996. He received an MSE in nuclear engineering from the University of Michigan in 1997, an MS in electrical engineering from Old Dominion University in 2003, and a PhD in nuclear engineering from the University of Michigan in 2006. He was an active duty Naval officer from 1997 to 2003 and is currently a Captain in the Navy Reserves. From 2006 to 2012, he was an electromagnetic physicist at GE Global Research Center. He joined Purdue University in 2012, where he is currently an Associate Professor and Undergraduate Program Chair of Nuclear Engineering.
Garner received a University of Michigan Reagents’ Fellowship and a National Defense Science and Engineering Graduate Fellowship. He has been awarded two Meritorious Service Medals, the Navy and Marine Corps Commendation Medal, and five Navy and Marine Corps Achievement Medal. He also received the 2016 IEEE NPSS Early Achievement Award.
