Two-dimensional model of a strip detector with two tunnel junctions

The article describes a two-dimensional model of a strip X-ray detector with a superconducting absorbing strip and two tunnel junctions at its ends, The motion of nonequilibrium current carriers (quasiparticles) is considered in the framework of a diffusion equation with boundary conditions of third kind. The detector signals Q l and Q r and the spectral line shape are computed as a function of the strip size, quasiparticle capture efficiency in the tunnel junction, the quasiparticle loss parameter on the absorber lateral boundaries, and the quasiparticle recombination parameter R. Analytical solutions for the detector signals Q l and Q r are derived for the case R = 0. Numerical calculations are generally used. When boundary and recombination losses are allowed for, the detector signals turn out to depend on the photon absorption coordinate in the transverse direction. This broadens and distorts the spectral line shape. © 2012 Springer Science+Business Media, Inc.