New readout scheme for superconducting tunnel junction arrays

We report on the design and testing of a new readout scheme for Superconduc ting Tunnel Junction (STJ) arrays. This method drastically reduces the numb er of connections and electronic circuits required for reading out an array of pixelated detectors. In the specific case of STJs, it eases the manufac turing process and connectivity problems. It is a generic scheme in that it could also be applied to different kinds of detector arrays. The experimen ts reported are simply a proof of principle and were carried out on a two-b y-two array of STJs using optical photon excitation on tantalum-based detec tors. If one uses charge sensitive amplifiers with junction field-effect tr ansistors (JFETs) we verify that the resolution degrades mainly due to capa citance increase at the input node. However, since each detector is read-ou t by two independent circuits, these two outputs can be combined to increas e the signal-to-noise level. We show that the equivalent noise charge at th e input worsens by about a factor < N as compared to individual read-out an d for a N x N array, consistent with our theoretical predictions. If one us es Superconducting Quantum Interference Devices (SQUIDs) as pre-amplifying stage, there should be no considerable increase in electronic noise related to this new readout scheme. (C) 2000 Elsevier Science B.V. All rights rese rved.