Jonctions SIS en Nb/Al2O3/Nb pour des récepteurs en radioastronomie millimétrique et submillimétrique

To prepare radioastronomical missions on satellites, a balloon-borne experiment called PRONAOS-SMH is being developped under the responsability of the Centre National d'Etudes Spatiales. The 380 GHz SIS receiver is entirely prepared in our laboratory. The description of this project is made in the introduction. The first part explains the bases of the superconductivity, the Josephson effect and the SIS mixers. These concepts are very usefull to understand how the whole SIS receiver works. Then, the machines used for the junctions fabrications are described in a second part: the basic principles of evaporation, sputtering, etching and opticallithography are explained. A process of trilayer deposition to obtain small Nb/Al-AIOx/Nb SIS junctions (1 micron square) with excellent I/V characteristics, good reliability and high current densities is explained in the third part. To optimize this process, it has been usefull to develop several studies which are exposed here. The integration of these junctions in millimeter and submillimeter receivers is described in the part IV. The first results obtained with the 380 GHz receiver are promising : DSB receiver noise is 310K at 374GHz.Pour préparer les futures missions sur satellites en radioastronomie, le CNES est responsable d'un projet de ballon stratosphérique appelé PRONAOS-SMH pour lequel notre laboratoire doit construire le récepteur à 380 GHz. Ce projet est décrit dans l'introduction. Dans le premier chapitre, j'expose les bases de la supraconductivité, de l'effet Josephson et du fonctionnement du mélangeur SIS. Le chapitre II développe la technologie utilisée pour la fabrication des jonctions SIS: les principes de l'évaporation, de la pulvérisation, de la gravure et de la photolithographie y sont expliqués. Le troisième chapitre est plus particulièrement consacré à la description et à l'optimisation du procédé de fabrication des jonctions en Nb/AI-A1Ox/Nb. Des jonctions fiables de petite dimension (1 micron carré) et de forte densité de courant sont obtenues. Les études nécessaires pour parvenir à ce résultat sont détaillées. L'intégration de ces jonctions dans des récepteurs millimétriques et submillimétriques est décrite dans le chapitre IV. Les premiers résultats obtenus dans le récepteur à 380 GHz sont prometteurs : une température de bruit de 310 K DSB pour le récepteur dans son ensemble a été mesurée à 374 GHz

Tantalum STJ for Photon Counting Detectors

Superconducting Tunnel Junctions (STJ's) are currently being developed as photon detectors for a wide range of applications. Interest comes from their ability to cumulate photon counting with chromaticity (i.e. energy resolution) from the near infrared (2 $\mu$m) to the X-rays wavelengths and good quantum efficiency up to 80%. Resolving power can exceed 10 in the visible wavelength range. Our main goal is to use STJ's for astronomical observations at low light level in the near infrared. This paper put the emphasis on two main points: the improvement of the tantalum absorber epitaxy and the development of a new version of the fabrication process for making Ta/Al-AlOx-Al/Ta photon counting STJ's. The main features of this process are that pixels have aligned electrodes and vias patterned through a protecting SiO2 layer. These vias are then used to contact the top electrode layer. We use a double thin aluminum trapping layer on top of a 150 nm thick Ta absorber grown epitaxially. Photon counting experiments with Ta junction array are presented at \lambda = 0.78 $\mu$m. Digital filtering methods are used to compute the photon counting data in order to minimize the effects of noise

The numerical simulation tool for the MAORY multiconjugate adaptive optics system

The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is a hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implements the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and uses libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.Comment: 6 pages, 1 figure, Proceeding 9909 310 of the conference SPIE Astronomical Telescopes + Instrumentation 2016, 26 June 1 July 2016 Edinburgh, Scotland, U

The planar optics phase sensor: a study for the VLTI 2nd generation fringe tracker

In a few years, the second generation instruments of the Very Large Telescope Interferometer (VLTI) will routinely provide observations with 4 to 6 telescopes simultaneously. To reach their ultimate performance, they will need a fringe sensor capable to measure in real time the randomly varying optical paths differences. A collaboration between LAOG (PI institute), IAGL, OCA and GIPSA-Lab has proposed the Planar Optics Phase Sensor concept to ESO for the 2[SUP]nd[/SUP] Generation Fringe Tracker. This concept is based on the integrated optics technologies, enabling the conception of extremely compact interferometric instruments naturally providing single-mode spatial filtering. It allows operations with 4 and 6 telescopes by measuring the fringes position thanks to a spectrally dispersed ABCD method. We present here the main analysis which led to the current concept as well as the expected on-sky performance and the proposed design

High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

(abridged) A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT - the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope, a detector with a large field of view made of small movable CCDs located around a fixed central CCD, and an interferometric calibration system originating from metrology fibers located at the primary mirror. The proposed mission architecture relies on the use of two satellites operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations (alternative option uses deployable boom). The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits. The remaining time might be allocated to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member list of the NEAT proposal and the news about the project are available at http://neat.obs.ujf-grenoble.fr. The final publication is available at http://www.springerlink.co

MAORY real-time computer preliminary design

MAORY is the Multi-conjugate Adaptive Optics module for the Extremely Large Telescope and it will be located on the Nasmyth platform of the telescope to feed scientific instruments. MAORY will re-image the telescope focal plane providing multi-conjugate adaptive optics correction of the wavefront distortion induced by the atmosphere. The system is based on six laser guide stars and three natural guide stars for sensing the wavefront distortion and three deformable mirrors for correcting it. We will show the current status of the preliminary design of the Real Time Computer in charge of carrying out all the calculations based on the measurements of the guide stars wavefront sensors. The hard real time (primary) loops are in charge of controlling the deformable mirrors and the lasers jitter compensation while the soft real- time (secondary) loops are in charge of updating the primary loops parameters as well as measuring or estimating the atmospheric parameters and the system performance. Telemetry data management/recording and calibration are the other tasks carried out by the real time computer

The MAORY ICS software architecture

The Multi Conjugate Adaptive Optics RelaY (MAORY) for ESO's Extremely Large Telescope (ELT) is an adaptive optics module offering multi-conjugate (MCAO) and single-conjugate (SCAO) compensation modes. In MCAO, it relies on the use of up to six Laser Guide Stars (LGS) and three Natural Guide Stars (NGS) for atmospheric turbulence sensing and multiple mirrors for correction, providing high Strehl and high sky coverage. In SCAO mode, a single natural source is used as reference, providing better correction but in a smaller field. MAORY will be installed at the Nasmyth focus of the ELT. It will feed the MICADO first-light diffraction limited imager and a future second instrument. MAORY is being built by a Consortium composed by INAF in Italy and IPAG in France and is currently approaching end of phase B. In this paper we describe the preliminary design of the MAORY Instrument Control System Software (ICS SW). We start with an overview of the MAORY module and then describe the general architecture of the MAORY control network and software. We then describe the main software components, with particular emphasis to those managing the NGS and LGS wavefront sensors functions and the AO off-load and secondary loops, and the main interfaces to subsystems and external systems. We then conclude with a description of the software engineering practices adopted for the development of MAORY ICS SW

The MAORY laser guide star wavefront sensor: design status

MAORY will be the multi-adaptive optics module feeding the high resolution camera and spectrograph MICADO at the Extremely Large Telescope (ELT) first light. In order to ensure high and homogeneous image quality over the MICADO field of view and high sky coverage, the baseline is to operate wavefront sensing using six Sodium Laser Guide Stars. The Laser Guide Star Wavefront Sensor (LGS WFS) is the MAORY sub-system devoted to real-time measurement of the high order wavefront distortions. In this paper we describe the MAORY LGS WFS current design, including opto-mechanics, trade-offs and possible future improvements