KIP - Cryogenic particle detection - STJ

Superconducting Tunnel Junctions

This type of detector utilizes the enhancement of the quasi-particle current after the absorption of an incident particle (Fig. 1). Such a device consists in the simplest version of two superconducting electrodes deposited on a substrate, which are separated by a thin insulating layer. Since full thermalization is not needed, superconducting tunnel junctions (STJ) are fast and high counting rates are obtainable. Due to the fact that the particle have to be stopped in the thin superconducting electrodes the quantum efficiency is comparatively poor at high energies. In principle, an absorber can be used in connection with superconducting tunnel junctions, but in this case the speed of such detectors reduces to that of calorimetric detectors. Therefore the strength of STJ lies in the detection of low energy particles like soft x-rays (E < 1 keV) and uv-photons. Here some links to groups which develop and apply cryogenic detectors based on STJ:

Lawrence Livermore National Laboratory (USA)

Technische Universität München

European Space Agency (ESA)

Paul Scherrer Institut (PSI), Switzerland

University of Jyväskylä, Finland

University of Twente, Netherland

Fig. 1: Current voltage characteristics of a superconducting tunnel junction.