X-RAY RESPONSE OF NB-BASED SUPERCONDUCTING TUNNEL JUNCTION

Josephson tunnel junctions are well known as low temperature electroni cs devices. However, they are also important as very powerful sensors. A novel class of sensors is constituted by radiation detectors based on superconducting tunnel junctions, which could lead in next future t o an advanced instrumentation with an interesting applicative future. So far this area is restricted to low-temperature superconductors Seve ral superconducting materials have been considered, Among them, Niobiu m is very attractive because of its highest critical temperature T-c W e have measured detailed X-ray detection characteristics for Nb-based tunnel junction made with different fabrication processes. We will dis cuss the difference in the X-ray response in terms of the relevant jun ction's parameters, underlying the problems of the niobium as suitable material for this kind of device.