Upcoming Seminar: Effects of Surface Roughness on Electrical Contact, RF Heating and Field Enhancement
Posted on: September 30, 2011
Professor Y. Y. Lau
|Date||October 17, 2011|
|Location||1065 Kemper Hall|
Surfaces are never perfectly flat. Because of the surface roughness on a microscopic scale, true contact between two pieces of conductors occurs only at the asperities (small protrusions) of the two contacting surfaces, leading to contact resistance, an important issue to high power microwave sources, wire-array Z pinches, metal-insulator-vacuum junctions, field emitters, thin film devices and integrated circuits, and interconnects, etc. Surface roughness may also cause enhanced RF absorption on the surface, an important consideration for MW gyrotron and for the development of THz source. Another profound effect of surface roughness is the excessive local electric field enhancement that triggers RF breakdown. In a superconducting cavity, surface roughness is known to cause local magnetic field enhancement that leads to abrupt quenching, i.e., rapid loss of superconductivity.
This talk features recent advances made at the University of Michigan on the modeling of various effects of surface roughness, including electrical contact resistance for both bulk contacts and thin film contacts. Scaling laws are constructed for a large range of resistivity ratios and geometries in the contact members. Also presented is roughness-induced enhanced RF heating, and the enhanced RF electric and magnetic fields.
Y. Y. Lau received the S.B., S.M., and Ph.D. degrees in electrical engineering from the Massachusetts Institute of Technology (MIT). He was Assistant Professor in applied mathematics at MIT, and a research physicist at the US Naval Research Laboratory, before joining the University of Michigan, Ann Arbor as a Professor with the Department of Nuclear Engineering and Radiological Sciences. He has worked on electron beams, coherent radiation sources, plasmas, and discharges. He is the author of 190 refereed publications and ten patents. He is Fellow of the American Physical Society and of IEEE. He received the 1999 IEEE Plasma Science and Applications Award, and served as an Associate Editor for the Physics of Plasmas.