Annular Josephson junctions for radiation detection: fabrication and investigation of the magnetic behaviour

We have fabricated and characterised superconducting tunnel junctions with annular geometry for radiation detection. The advantage of the annular geometry is that, once the trapping has occurred the magnetic field can be switched off and there is no need to further sustain any parallel magnetic field during the detector working time. In agreement with our previous theoretical prediction we have observed the suppression of the Josephson critical current and the presence of one single resonance step in the I–V characteristic when magnetic fluxons were trapped in the central hole of the junction.