Improving the freshman electrical and computer engineering lab

This thesis covers the challenges of creating and maintaining an introductory engineering laboratory. The history of the University of Illinois Electrical and Computer Engineering department’s introductory course, ECE 110, is recounted. The current state of the course, as of Fall 2008, is discussed along with current challenges arising from the use of a hand-wired prototyping board with logic gates. A plan for overcoming these issues using a new microcontroller-based board with a pseudo hardware description language is discussed. The new microcontroller based system implementation is extensively detailed along with its new accompanying description language. This new system was tried in several sections of the Fall 2008 semester alongside the old system; the students’ final performances with the two different approaches are compared in terms of design, performance, complexity, and enjoyment. The system in its first run shows great promise, increasing the students’ enjoyment, and improving the performance of their designs.

Superconducting Transition-Edge Sensor Physics

Despite record-setting performance demonstrated by superconducting Transition Edge Sensors (TESs) and growing utilization of the technology, a theoretical model of the physics governing TES devices superconducting phase transition has proven elusive. Earlier attempts to describe TESs assumed them to be uniform superconductors. Sadleir et al. 2010 shows that TESs are weak links and that the superconducting order parameter strength has significant spatial variation. Measurements are presented of the temperature T and magnetic field B dependence of the critical current Ic measured over 7 orders of magnitude on square Mo/Au bilayers ranging in length from 8 to 290 microns. We find our measurements have a natural explanation in terms of a spatially varying order parameter that is enhanced in proximity to the higher transition temperature superconducting leads (the longitudinal proximity effect) and suppressed in proximity to the added normal metal structures (the lateral inverse proximity effect). These in-plane proximity effects and scaling relations are observed over unprecedentedly long lengths (in excess of 1000 times the mean free path) and explained in terms of a Ginzburg-Landau model. Our low temperature Ic(B) measurements are found to agree with a general derivation of a superconducting strip with an edge or geometric barrier to vortex entry and we also derive two conditions that lead to Ic rectification. At high temperatures the Ic(B) exhibits distinct Josephson effect behavior over long length scales and following functional dependences not previously reported. We also investigate how film stress changes the transition, explain some transition features in terms of a nonequilibrium superconductivity effect, and show that our measurements of the resistive transition are not consistent with a percolating resistor network model.