Investigation of n-values of composite superconductors

Knowledge of the voltage-current characteristics of composite superconductors is very important for the development of superconducting high-field magnets, especially NMR magnets. These curves are characterized by the n-values and were systematically investigated for NbTi, (NbX)(3)Sn with additional components, X, and BSSCO-2223 composite superconductors by the standard four-point measurement technique. The influence on n-values of coating the NbTi filaments with Nb as well as the dependence of n-values on the internal structure of composite NbTi and (NbX)(3)Sn superconductors will be presented. The n-values of Nb3Sn are discussed under the aspect of the heat treatment parameters reaction time and reaction temperature. The n-values of various BSCCO-2223 superconductors will also be compared.