A superconducting tunnel junction X-ray detector design for practical applications

Superconducting tunnel junctions coupled to a superconducting absorber can be used as a high-resolution energy-disperisive X-ray detector. The energy of an absorbed X-ray breaks Cooper pairs in the absorber, producing quasiparticles. These quasiparticles can tunnel through the barrier and be counted. When used in conjunction with FET electronics, however, the noise requirements limit the area of the tunnel junction. In many designs, this also limits the absorber area. We present a detector design that separates the absorber from the junction. It features a tantalum absorber for high absorption efficiency and an aluminum transport layer for rapid, low loss transport to the junction. Transport is aided by multiple trapping stages, while fabrication is simplified by using only two materials.