Dynamics of nonequilibrium quasiparticles in a double superconducting tunnel junction detector

TL;DR

This paper investigates the behavior of nonequilibrium quasiparticles in a simplified superconducting detector without traps, analyzing their diffusion dynamics to understand signal formation and detector potential.

Contribution

It introduces an analytical model for quasiparticle diffusion in a trap-free superconducting detector, enhancing understanding of signal dynamics without the complexity of traps.

Findings

Quasiparticles obey a position-dependent diffusion equation.

Analytical solutions predict quasiparticle dynamics and signal formation.

The simplified model offers insights into detector potential without traps.

Abstract

We study a class of superconductive radiation detectors in which the absorption of energy occurs in a long superconductive strip while the redout stage is provided by superconductive tunnel junctions positioned at the two ends of the strip. Such a device is capable both of imaging and energy resolution. In the established current scheme, well studied from the theoretical and experimental point of view, a fundamental ingredient is considered the presence of traps, or regions adjacent to the junctions made of a superconducting material of lower gap. We reconsider the problem by investigating the dynamics of the radiation induced excess quasiparticles in a simpler device, i.e. one without traps. The nonequilibrium excess quasiparticles can be seen to obey a diffusion equation whose coefficients are discontinuous functions of the position. Based on the analytical solution to this equation, we follow the dynamics of the quasiparticles in the device, predict the signal formation of the detector and discuss the potentiality offered by this configuration.