Development of Superconducting NbSi TES Array and Associated Readout With SQUIDs and Integrated Circuit Operating at 2 K

Abstract

To further increase the sensitivity of future telescope projects dedicated to photometric astronomy observation at millimeter and sub-millimeter wavelengths, large number of bolometer is currently developed. In this context, The DCMB (Developement Concerte de Matrice de Bolometre) French collaboration makes an R&D effort to develop large bolometer arrays. This paper concentrates on a first demonstration of NbSi TES (transition-edge sensors) array development: a 23 NbSi (niobium silicon) superconducting thermometer array. Firstly, the NbSi thin film alloy is described then the 23 TES array topology is presented. The readout of large TES arrays requires ultra low noise amplification and multiplexing electronics. The use of a first stage transducer such as a SQUID (superconducting quantum interference device) allows ultimate performances in terms of noise. However, the linearization of the SQUID characteristic requires a low noise amplifier (LNA) to generate a flux lock loop (FLL). We implement this component in a cryogenic SiGe integrated circuit (IC) that could also contains the control of the multiplexing. Using this readout chain, a one-pixel operation using NbSi thermometer readout by SQUID and a cryogenic LNA is demonstrated. Finally, the development of a specific cryogenic IC including amplifiers, addressing and switching current sources needed for a 24 to 1 time domain SQUID multiplexer is presented.