Sustainable Energy, Superconducting Materials
Dr. Chiesa's primary research interest is superconducting materials for energy applications. Superconducting materials are alloys or ceramic compounds that can carry much higher currents than conventional copper materials and this characteristic make them very well suited for large powerful magnets applications and power storage and delivery systems.
Among the applications of interest for Dr. Chiesa's research are fusion storage systems. Superconducting materials are characterized by three critical properties: current, field and temperature so that in order to have superconductivity we need to be underneath the critical surface described by those three properties. Superconductors are divided in two categories: Low Temperature Superconductors (LTS) and High Temperature Superconductors (HTS) according to their critical temperature being below or above 77 K respectively. LTS are typically used in magnet applications while HTS are used in transmission lines and more recently magnets.
One of the challenges for any applications using superconducting materials is that the performance of superconductors is greatly affected by strain and degradation of their properties is observed when load is applied. Cables used for the technologies described above are composed of several hundreds of strands and describing the interaction among all those strands is a very complex problem. Also the interaction of current and field of those strands during operations create large forces on the materials so it is inevitable that they experience some type of load when used.
The focus of Dr. Chiesa's research is to understand better the electromechanical behavior of superconducting materials under loading conditions that are similar to the ones experienced during operations. Tests on full size cables would be extremely expensive and impractical at the laboratory level so typically experiments are done on single strand or small cables and then the information found are extrapolated to the full size cable and the extrapolation process is a key topic of interest. The main experimental activities performed in Dr. Chiesa's lab, focus on the characterization of superconducting wires and cables through the design and test of custom built experiments to apply pure bending and transverse forces on samples. The probes used for the experiments are designed and built at Tufts University and the experiments performed at the National High Magnetic Field Laboratory. Measurements of critical currents as a function of the load applied are typically performed to characterize the samples. Models are then used to better understand the behavior of superconducting materials and predict the behavior of large cables.