Response of an On-Chip Coil-Integrated Superconducting Tunnel Junction to X-rays

An on-chip coil-integrated superconducting tunnel junction (OC2-STJ) was irradiated by X-rays emitted from an 55Fe source to the examine the performance of X-ray detection by applying a magnetic field produced by a superconducting microstrip coil integrated into the junction chip. Response characteristics were obtained for a diamond-shaped Nb-based tunnel junction with a sensitive area of 100×100 µm2 in the OC2-STJ chip. Two kinds of stable operation modes with different pulse heights were observed by changing the magnetic flux density in the barrier region of the junction. In the low-pulse-height mode, the pulse height distribution exhibits two full-energy peaks corresponding to signals created in the top and base electrodes. Stable operation of the OC2-STJ was demonstrated without using conventional external electromagnets.