High-Tc superconductors at high current densities

The development of a new measurement technique has enabled new insights into the behavior of high-Tc superconductors under intense current. The most exciting property of a superconductor is it`s ability to conduct electricity without resistance and without losses of energy flowing through the material. Once set in motion electrical current will flow forever in a closed loop of superconducting material, provided that certain limits are not exceeded. This effect can be used technically, for instance, to create a large permanent magnetic field. Many other possible applications in the electric power industry, in precision measurement technology, ultrafast electronic circuits and computing can profit from the material`s unique property of conducting electric energy without dissipation. The particular advantage of the new superconductors is that the operating temperature, which has to be below a certain critical temperature, can be readily achieved by available cooling technology. Therefore these materials are named "high-Tc superconductors". The new superconductors can carry extremely high, but not unlimited currents. At such high current densities conventional metals would melt immediately. In the course of this project the properties of high-Tc superconductors near or above this limiting critical current have been studied extensively. A novel measurement method was developed that allows to perform the measurement within one twentieth part of a millionth of a second, which is to-date the fastest apparatus of this kind in the world. It avoids the detrimental heating effects when the critical current is surpassed during the experiment. With this experimental conditions that have not been explored previously several novel effects have been found and successfully compared to our new theoretical explanations. The investigations were performed in collaboration with research groups in Austria, France, Italy, Russia, and USA and are expected to have impact on the development of commercial application of high-Tc superconductors that operate at high currents, such as power transmission lines and fault current limiters.