Benoit Belier

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

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.

Large submillimeter and millimeter detector arrays for astronomy: development of NbSi superconducting bolometers

The achievement of the Planck and Herschel space missions in the submillimeter and millimeter range was made possible by a continuous effort on detector developments. Now limited by the intrinsic fluctuations of the radiation coming from the astronomical sources themselves, the sensitivity improvement requires the development of large arrays of detectors filling the focal plane of the telescopes. We present here the development of a TES array using NbSi sensors on SiN membranes. The readout electronics is based on SQUIDs and a cooled SiGe ASIC multiplexer. The detector is coupled with the input radiation by means of antenna. The present goal performance is adapted for the realisation of a ground based millimeter camera.

TSF Experiment for comparision of high Reynold’s number turbulence in He I and He II : first results.

Superfluid turbulence (TSF) project uses liquid helium for the fundamental study of turbulent phenomena behind a passive grid and is able to work both in HeI and in HeII. Local and semi-local instrumentation was developed specifically for the purpose of this experiment(e.g. sub-micrometer anemometer, total head pressure tube and second sound tweezer). The difficulties encountered with this local and fragile instrumentation are discussed. Global characterization of the flow is presented including velocity, pressure, temperature stability and turbulence intensity. Finally, first results obtained with semi local measurements (total head pressure tube and second sound tweezer) both in the two phases of helium are presented.

Design and fabrication of arrays of nanoelectromechanical resonators for parallel detection of biomolecular interactions

The recent achievements of surface and bulk micro and nanomachining techniques combined with the fabrication techniques of integrated circuits have led to the development of miniaturized sensors and actuators exhibiting unprecedented sensitivity. This work is dedicated to the design and fabrication of nanoelectromechanical resonators for parallel detection of biomolecular interactions. The aim is to obtain piezoresistive nanoresonators with a high mechanical quality factor and a high force sensitivity to detect the mass loading induced by specific biomolecular interactions (ligand-receptor, antibody-antigen, hybridization of complementary DNA strands).

NbSi TES Array and Readout: Development and Characterization

We are developing a detection system based on a NbSi Transition Edge Sensor (TES) bolometer array. A thermo-mechanical architecture accomodates the array and the cryogenic stage of the readout. We model the coupling of the TES bolometer to the radiation by means of twin slot antenna. We present the latest design of the cryogenic readout which includes a BiCMOS SiGe integrated circuit at 4 K controlling a Superconducting Quantum Interference Device (SQUID) amplifier.

Characterization of NbSi TES on a 23-Pixel Array

Instrumental progress allowed the development of bolometric detectors adapted to submillimeter and millimeter wavelengths. Superconducting transition-edge sensors (TESs) are currently under heavy development to be used as ultra sensitive bolometers. In addition to good performance, the choice of material depends on long term stability (both physical and chemical) along with a good reproducibility and uniformity in fabrication. For this purpose we are investigating the properties of NbSi thin films and have already developed arrays of NbSi TES. NbSi is a well-known alloy for use in resistive thermometers. We present a low temperature characterization of the NbSi films on a 23-pixel array. In order to tune the critical temperature of the NbSi thermometers down to the desired range, we have to adjust the concentration of Niobium in the NbSi alloy. In this experiment, we set for a Niobium concentration of 15 percent, to be able to run tests at a convenient temperature larger than 300 miliKelvin. Tests are made using Helium4-cooled cryostats, 300 miliKelvin Helium3 mini-fridges, resistance bridge and a commercial SQUID with its readout circuit. Parameters being measured are: critical temperature, resistance, sharpness of the transition given by the alpha parameter and noise measurements. The multiplexing is also developed to prepare the final chain for noise measurements on 23 pixel bolometers array.

Characterization of NbSi films for TES bolometers

Future space experiments will require large arrays of sensitive detectors in the submillimeter and millimeter range. Superconducting transition-edge sensors (TESs) are currently under heavy development to be used as ultra sensitive bolometers. In addition to good performance, the choice of material depends on long term stability (both physical and chemical) along with a good reproducibility and uniformity in fabrication. For this purpose we are investigating the properties of co-evaporated NbSi thin films. NbSi is a well-known alloy for use in resistive thermometers. We present a full low temperature characterization of superconductive NbSi films. In order to tune the critical temperature of the NbSi thermometers down to the desired range, we have to adjust the concentration of niobium in the NbSi alloy. Tests are made using 4He-cooled cryostats, 300mK 3He mini-fridges, Resistance Bridges and commercial SQUID. Measured parameters are the critical temperature, the sharpness of the transition. Noise measurements are on-going.

Design and simulation of an antenna-coupled TES bolometer

We present a new design of an antenna-coupled superconducting transition-edge sensor (TES) bolometer. The incident radiation is coupled to a membrane-based twin-slot antenna and then transmitted through lossless microstrip lines to lossy meander-like microstrip lines in which a NbSi film is located between strip and dielectric layer. The NbSi film serves as both power absorber and temperature sensor (thermometer). With the help of the electromagnetic simulation software High Frequency Structure Simulator (HFSS), we have studied the performance of the twin-slot antenna. The simulation results for radiation pattern and return loss show promising prospects for this TES bolometer design. The power absorption in NbSi film is another important aspect which will be modeled in the future.

Development of NbSi TES bolometer arrays for submillimeter astronomy

Future ground and space astronomy experiments will require large arrays of sensitive detectors in the submillimeter and millimeter ranges. Superconducting Transition Edge Sensors (TES) are currently under development in many institutes to be used as ultra sensitive bolometers. We are investigating co-evaporated NbSi thin films TES arrays. We present here the characterisation and laboratory performances of an array and its readout electronics.