Optimization of superconducting tunnel junction based x-ray detectors
Publication date: 01 Dec 1993
Authors: Foden, C.L., et al.
Journal: Journal of Applied Physics
Copyright: American Institute of PhysicsCurrent research into x-ray detection using superconducting tunnel junctions indicates that the poor spectral resolution obtained so far, in comparison with theoretical expectations, is partly due to the excellent acoustic coupling of the junction and substrate. The substrate acts both as a source of noise and as a heat sink for the nonequilibrium junction, thus masking the intrinsic response of the superconducting electrodes to photoexcitation. A new design for a superconducting tunnel junction based on an x-ray detector is presented. The design effectively decouples the substrate and junction and should therefore eliminate many causes of spectral degradation, bringing resolution closer to that predicted theoretically, and thus allowing experimental investigation of the intrinsic superconducting film response to x-ray photoexcitation. An outline of the way in which the design can be optimized geometrically to achieve the decoupling is given. Further optimization of the intrinsic film response to x-ray photons is achieved through the introduction of specific absorbing and trapping regions to improve both the quantum efficiency and charge output of the new design. The use of "pairing potential barriers" within the electrode leads will also improve the intrinsic resolution of this device.