M. Piat

Latest Progress on the QUBIC Instrument

QUBIC is a unique instrument that crosses the barriers between classical imaging architectures and interferometry taking advantage from both high sensitivity and systematics mitigation. The scientific target is to detect primordial gravitational waves created by inflation by the polarization they imprint on the cosmic microwave background—the holy grail of modern cosmology. In this paper, we show the latest advances in the development of the architecture and the sub-systems of the first module of this instrument to be deployed at Dome Charlie Concordia base—Antarctica in 2015.

Cryogenic SiGe ASICs for readout and multiplexing of superconducting detector arrays

This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuits (ASICs : Application Specific Integrated Circuits). We have designed successively two ASICs in standard BiCMOS SiGe 0.35 μm technology that have proved to be operating at cryogenic temperatures. The main functions of these circuits are the readout and the multiplexing of SQUID/TES arrays. We report the cryogenic operation of a first ASIC version dedicated to the readout of a 2×4 pixel demonstrator array. We particularly emphasize on the development and the test phases of an ultra low noise (0.2 nV/√Hz) cryogenic amplifier designed with two multiplexed inputs. The cryogenic SiGe amplifier coupled to a SQUID in a FLL operating at 4.2 K is also presented. We finally report on the development of a second version of this circuit to readout a 3×8 detectors array with improved noise performances and upgraded functionalities.

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.

The Planck high-frequency instrument: a third-generation CMB probe and the first submillimeter surveyor

The High Frequency Instrument of the Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB). Its main goal is to map the CMB with a sensitivity of ΔT/T=2.10-6 and an angular resolution of 5 arcmin in order to constrain cosmological parameters. Planck is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The architecture of the satellite is driven by the thermal requirements resulting from the search for low photon noise. Especially, the passively cooled telescope should be at less than 50K, while a cascade of cryo-coolers will ensure the cooling of the HFI bolometers down to 0.1K. This last temperature will be produced by a gravity insensitive 3He/4He dilution cooler. This will be achieved at the L2 Lagrangian point of the Sun-Earth system. The whole sky will be observed two times in the 14 months mission with a scanning strategy based on a 1RPM rotation of the satellite. In addition to the cosmological parameters that can be derived from the CMB maps, Planck will deliver nine high sensitivity submillimeter maps of the whole sky that will constitute unique data available to the whole astronomical community.

Planck-HFI thermal architecture: from requirements to solutions

The Planck-High Frequency Instrument (HFI) will use 48 bolometers cooled to 100mK by a dilution cooler to map the Cosmic Microwave Background (CMB) with a sensitivity of ΔT/T~2.10-6 and an angular resolution of 5 minutes of arc. This instrument will therefore be about 1000 times more sensitive than the COBE-DMR experiment. This contribution will focus mainly on the thermal architecture of this instrument and its consequences on the fundamental and instrumental fluctuations of the photon flux produced on the detectors by the instrument itself. In a first step, we will demonstrate that the thermal and optical design of the HFI allow to reach the ultimate sensitivity set by photon noise of the CMB at millimeter wavelength. Nevertheless, to reach such high sensitivity, the thermal behavior of each cryogenic stages should also be controlled in order to damp thermal fluctuations that can be taken as astrophysical signal. The requirement in thermal fluctuation on each stage has been defined in the frequency domain to degrade the overall sensitivity by less than 5%. This leads to unprecedented stability specifications that should be achieved down to 16mHz. We will present the design of the HFI thermal architecture, based on active and passive damping, and show how its performances were improved thanks to thermal simulations.

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.

SiGe Integrated Circuit/SQUID Hybrid Cryogenic Multiplexer for Superconducting Bolometer Array

The development of large superconducting bolometer (Transition Edge Sensor: TES) arrays requires ultra low noise amplification and multiplexing electronics. The use of a first transducer stage such as a SQUID (Superconducting QUantum Interference Device) allows ultimate performance in terms of noise. However, the linearization of the SQUID characteristic requires low noise amplification. Furthermore, to realize a time domain multiplexer with SQUIDs, switched biasing is also needed. We have designed an Integrated Circuit (IC) in standard BiCMOS SiGe technology for the readout and the control of a SQUID multiplexer. It includes a low noise amplifier with multiplexed inputs, switched current sources for SQUIDs, and digital circuit for the addressing with only one room temperature clock signal. We have successfully tested this integrated circuit down to 2 K. To validate the operation of a SQUID multiplexer controlled by this SiGe cryogenic IC, we have developed a 2×2 SQUID hybrid demonstrator. It consists of ...

Simulation of the Planck-HFI thermal control system

The core of the High Frequency Instrument (HFI) on-board the Planck satellite consists of 52 bolometric detectors cooled at 0.1 Kelvin. In order to achieve such a low temperature, the HFI cryogenic architecture consists in several stages cooled using different active coolers. These generate weak thermal fluctuations on the HFI thermal stages. Without a dedicated thermal control system these fluctuations could produce unwanted systematic effects, altering the scientific data. The HFI thermal architecture allows to minimise these systematic effects, thanks to passive and active control systems described in this paper. The passive and active systems are used to damp the high and low frequency fluctuations respectively. The results of the simulation of these active and passive control systems are presented here. These simulations based on the use of thermal transfer functions for the thermal modelling can then be used for finding the optimal working point of the HFI PID active thermal control system.

The High Frequency Instrument of Planck: Requirements and Design

The Planck satellite is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. It is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB) with unprecedented sensitivity and angular resolution. The detectors of its High frequency Instrument (HFI) are bolometers cooled down to 100 mK. Their sensitivity will be limited by the photon noise of the CMB itself at low frequencies, and of the instrument background at high frequencies. The requirements on the measurement chain are directly related to the strategy of observation used for the satellite. Due to the scanning on the sky, time features of the measurement chain are directly transformed into angular features in the sky maps. This impacts the bolometer design as well as other elements: For example, the cooling system must present outstanding temperature stability, and the amplification chain must show, down to very low frequencies, a flat noise spectrum.

Next generation sub-millimeter wave focal plane array coupling concepts: An ESA TRP project to develop multichroic focal plane pixels for future CMB polarization experiments

The main objective of this activity is to develop new focal plane coupling array concepts and technologies that optimise the coupling from reflector optics to the large number of detectors for next generation sub millimetre wave telescopes particularly targeting measurement of the polarization of the cosmic microwave background (CMB). In this 18 month TRP programme the consortium are tasked with developing, manufacturing and experimentally verifying a prototype multichroic pixel which would be suitable for the large focal plane arrays which will be demanded to reach the required sensitivity of future CMB polarization missions. One major development was to have multichroic operation to potentially reduce the required focal plane size of a CMB mission. After research in the optimum telescope design and definition of requirements based on a stringent science case review, a number of compact focal plane architecture concepts were investigated before a pixel demonstrator consisting of a planar mesh lens feeding a backend Resonant Cold Electron Bolometer RCEB for filtering and detection of the dual frequency signal was planned for manufacture and test. In this demonstrator the frequencies of the channels was chosen to be 75 and 105 GHz in the w band close to the peak CMB signal. In the next year the prototype breadboards will be developed to test the beams produced by the manufactured flat lenses fed by a variety of antenna configurations and the spectral response of the RCEBs will also be verified.