Selected issues concerning the influence of irradiation on the characteristics of superconducting elements in modern FELs facilities

This paper discusses issues of using superconductors in modern accelerators, such as free-electron laser type, in a radioactive environment. It shows how irradiation damages the subtle structure of superconducting materials, especially 1D and 2D high-temperature superconductors, in which it leads to the creation of nano-sized columnar-type defects. The influence of the radiation-induced structural defects on the current-carrying properties of the superconducting materials is investigated according to a developed energetic description of the capturing process on these defects, acting as pinning centres of magnetic pancake vortices. Various initial positions of the captured vortices are analysed. The influence of the irradiationinduced defects on the current-voltage characteristics is investigated, and the maximum current density is determined as a function of irradiation intensity and such physical parameters as magnetic field, temperature, and nano-defect size. This analysis is therefore of scientific interest and should also be helpful in determining the proper operating conditions of solenoids and other superconducting elements in free-electron laser facilities.