Superconducting tunnel junction detectors: Analysis of the linear regime

A theoretical analysis of the linear regime in a superconducting tunnel junction (STJ) has been carried out on the basis of a kinetic approach to the non-equilibrium superconductivity induced in the detector by an X-ray. A solution of the diffusive equation of the quasi-particles has been obtained assuming very slow recombination processes and an equilibrium 2Δ-phonon distribution. Under these conditions, the response of the detector is linear, that is the charge collected by the detector itself is proportional to the energy released. A relation between this released energy and the collected charge has also been obtained, thus achieving an expression of the mean energy ε{lunate} per excess quasi-particle. A comparison with some experimental results taken from current literature has been also reported. © 1991.

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