Empirical characteristics of tunnel junctions for X-ray detection

Superconducting tunnel junctions show an excellent energy resolution in X-ray detection. A simple procedure is employed to give an overview of the detector characteristics regardless of superconductor materials such as Al, Sn and Nb. By introducing an empirical relationship between junction parameters, the detector characteristics of signal magnitude and energy resolution are reproduced to an acceptable degree. This method gives helpful suggestion for understanding detector performance, and also serves as a guide line for designing tunnel junctions.