Experimental imaging diagnosis of superconducting tunnel junction x-ray detectors by low-temperature scanning synchrotron microscope

Imaging diagnosis of superconducting tunnel junction x-ray detectors has be en performed by an apparatus called the low-temperature scanning synchrotro n microscope (LTSSM) using an x-ray microbeam with a diameter of 5-10 mum o riginated from synchrotron radiation. Quasiparallel intense synchrotron rad iation enables one to obtain the full two-dimensional images of junctions w ith dimensions of 200x200 mum(2) in about 1 h. The LTSSM results indicate t hat the standard quasiparticle diffusion and edge loss model for the spatia l distribution of the junction response to x rays is evidently inadequate f or intermediate or large junctions (with respect to a Josephson penetration depth). On this basis, it is argued that the models proposed for the signa l creation and loss mechanism should be reconsidered. (C) 2000 American Ins titute of Physics. [S0003-6951(00)01650-8].