Performance of NbSi transition-edge sensors readout with a 128 MUX factor for the QUBIC experiment

SALATINO, M ET AL.; C. G. SCOCCOLA

Texas

Conferencia; SPIE Astronomical Telescopes & Instrumentation coference; 2018

QUBIC (the Q and U Bolometric Interferometer for Cosmology) is aground-based experiment which seeks to improve the current constraintson the amplitude of primordial gravitational waves. It exploits theunique technique, among Cosmic Microwave Background experiments, ofbolometric interferometry, combining together the sensitivity ofbolometric detectors with the control of systematic effects typical ofinterferometers. QUBIC will perform sky observations in polarization, intwo frequency bands centered at 150 and 220 GHz, with two kilo-pixelfocal plane arrays of NbSi Transition-Edge Sensors (TES) cooled down to350 mK. A subset of the QUBIC instrument, the so called QUBICTechnological Demonstrator (TD), with a reduced number of detectors withrespect to the full instrument, will be deployed and commissioned beforethe end of 2018. The voltage-biased TES are read out with Time DomainMultiplexing and an unprecedented multiplexing (MUX) factor equal to128. This MUX factor is reached with two-stage multiplexing: atraditional one exploiting Superconducting QUantum Interference Devices(SQUIDs) at 1K and a novel SiGe Application-Specific Integrated Circuit(ASIC) at 60 K. The former provides a MUX factor of 32, while the latterprovides a further 4. Each TES array is composed of 256 detectors andread out with four modules of 32 SQUIDs and two ASICs. A custom softwaresynchronizes and manages the readout and detector operation, while theTES are sampled at 780 Hz (100kHz/128 MUX rate). In this work wepresent the experimental characterization of the QUBIC TES arrays andtheir multiplexing readout chain, including time constant, criticaltemperature, and noise properties.