LINC-NIRVANA: MCAO toward Extremely Large Telescopes

LINC-NIRVANA is a Fizeau (imaging) interferometer exploiting the full spatial resolution of a 23 m class telescope in the combined beam of the Large Binocular Telescope supported through Multi-Conjugated Adaptive Optics (MCAO). By means of science cases, we show how LINC-NIRVANA takes advantage of the MCAO, increasing the sky coverage of the instrument and the field of view for the Fringe and Flexure tracker. We introduce the MCAO system of LINC-NIRVANA in detail, which in a first step will be installed with two deformable mirrors per arm and has the provision to be upgraded with a third mirror. The MCAO system implements several novel concepts proposed for extremely large telescopes, such as layer oriented MCAO, optical co-adding of guide stars, or Multiple Field of View sensing. LINC-NIRVANA will demonstrate some of the concepts for the first time on sky. To cite this article: W. Gaessler et. al., C. R. Physique 6 (2005).     

MAD: practical implementation of MCAO concepts

The European Southern Observatory (ESO) together with external research institutes have built a Multi-Conjugate Adaptive Optics (MCAO) Demonstrator (MAD) to perform wide field-of-view adaptive optics correction (2′ in K band). The aim of MAD is to demonstrate the on-sky feasibility of the MCAO technique and to evaluate its critical aspects in the framework of both the 2nd generation instrumentation for the Very Large Telescope (VLT) and the Overwhelmingly Large Telescope (OWL). The MAD module will be installed on the VLT to perform on-sky observations. MAD comprises two deformable mirrors and two different multi-reference wavefront sensors with natural guide stars. In this article we present the MAD design, some aspects of the MAD calibration and the first closed-loop results in the laboratory in Single Conjugated Adaptive Optics (SCAO) and Ground Layer Adaptive Optics (GLAO) configurations. To cite this article: E. Marchetti et al., C. R. Physique 6 (2005).     

Optimal control for Multi-Conjugate Adaptive Optics

Classic adaptive optics (AO) is now a proven technique that provides a closed loop real time correction of the turbulence. It is generally based on simple and efficient control algorithms. The next AO generation (Multi-Conjugate AO (MCAO) in its various forms and Extreme AO (XAO)) will require more sophisticated control approaches, especially in the case of wide field AO. We present here the concepts behind optimal control. The advantages compared to more standard approaches are stressed. A first experimental validation is presented. To cite this article: C. Petit et al., C. R. Physique 6 (2005).     

Simulation of MCAO on (extremely) large telescopes

In this article, we describe the different methods to simulate Multi-Conjugate Adaptive Optics (MCAO) systems. First, analytical (error-budget type) and semi-analytical (Fourier) methods are described. We then describe the different modules required to make end-to-end (Monte Carlo) simulations of these systems. Finally, we present some of the computational challenges associated with the simulation of MCAO on Extremely Large Telescopes (ELTs). To cite this article: M. Le Louarn et al., C. R. Physique 6 (2005).     

Multi-conjugate solar adaptive optics at the Vacuum Tower Telescope on Tenerife

We present a breadboard multi-conjugate adaptive optics (MCAO) system for high angular resolution solar observations which we operate at the Vacuum Tower Telescope. We have developed methods to estimate quantitatively the performance of solar adaptive optics from science data. Several sets of short exposure images of the solar photosphere were analyzed to assess the performance of the MCAO. We demonstrate that a 30 arcsec field of view is substantially improved when the MCAO system is turned on. This compares favourably with an improvement of a 10 arcsec field with conventional solar adaptive optics. We also show how irradiance fluctuations in the MCAO compensated focus can be suppressed. To cite this article: O. von der Lühe et al., C. R. Physique 6 (2005).     

On practical aspects of Laser Guide Stars

The Gemini Observatory has developed an extensive Adaptive Optics (AO) program, including Classical AO, Laser Guide Star (LGS) AO, Multi-Conjugate AO (MCAO), extreme AO (eXAO) and Ground Layer AO (GLAO). Most of these instruments use one or several LGSs. A laser has been in operation at Gemini since May 2005. Most of the laser related systems (beam transport, launch, safety systems) have been developed in house. These are major components, requiring a development effort not to be underestimated. In this article, we propose to share the Gemini experience in terms of practical issues and calibration requirements associated with the use of lasers in AO. To cite this article: F. Rigaut, C. d'Orgeville, C. R. Physique 6 (2005).     

FALCON: multi-object AO

FALCON is a wide-field, multi-object integral field spectrograph equipped with adaptive optics. It is dedicated to the study of the formation process of primordial galaxies. The AO system uses natural guide stars, and the high sky coverage required for these studies is obtained using tomographic techniques for the wavefront analysis. The structure of the OA system is very new, and particularly suited for a future implementation on extremely large telescopes. To cite this article: E. Gendron et al., C. R. Physique 6 (2005).     

Multi-Conjugate Adaptive Optics for ELTs: constraints and limitations

We present how enlarging the size of a telescope from the current 10 meter telescope to the future 100 meter Extremely Large Telescopes increases the complexity of a classical or multiconjugate adaptive optics instrument. We point out elements or parameters of the system for which it is critical to propose new ideas as solutions and we study the effect of the increase of the diameter on the point spread function of an MCAO and a Ground Layer AO system. To cite this article: R. Ragazzoni et al., C. R. Physique 6 (2005).     

Fresnel phase matching: a universal phase matching scheme

We present new theoretical concepts for Fresnel phase matching. A guided wave approach is described, which allows us to intrinsically take into account all the physical processes involved. To cite this article: M. Raybaut et al., C. R. Physique 8 (2007).     

HgCdTe technology in France

SOFRADIR is one of the leading companies worldwide for the production of second generation InfraRed (IR) detectors. This success is due to the top level quality of the unique and production oriented French HgCdTe technology for manufacturing IR focal plane arrays based on an HgCdTe array and a CMOS readout and multiplexed silicon array. This technology and main products are presented in this paper. Finally, in order to prepare for future military and industrial needs, SOFRADIR has been working in close relationship with CEA-LETI/LIR on third generation developments based on HgCdTe material using Molecular Beam Epitaxy (MBE) growth. To cite this article: P. Tribolet, C. R. Physique 4 (2003).     

Metamaterials and invisibility

Metamaterials have significantly extended the range of electromagnetic properties available to device designers. An interesting application of these new materials is to the problem of cloaking, where the goal is to render an object invisible to electromagnetic radiation within a certain frequency range. Here, I review the concepts behind recently-proposed invisibility cloaks, and the way in which metamaterials can allow these designs to be realized. To cite this article: B. Wood, C. R. Physique 10 (2009).     

Semiclassical integrability in AdS/CFT

Integrable structures on both sides of the AdS/CFT correspondence are reviewed, with emphasis on the Bethe ansatz. To cite this article: K. Zarembo, C. R. Physique 5 (2004).

Résumé

Des structures intégrables de chaque coté de la correspondance AdS/CFT sont rappelées, avec un accent sur la conjecture de Bethe. Pour citer cet article : K. Zarembo, C. R. Physique 5 (2004).     

Ground Layer Adaptive Optics

We will introduce the present knowledge of the turbulence profile and in particular we will emphasise the existence of a turbulence layer close to the ground. Then we will present the concept of Ground Layer Adaptive Optics and will provide estimates of performance expected from such systems and their potential for astronomical applications. Finally we will provide practical implementation concepts for two instruments at the VLT, MUSE and HAWK-I using multi-Laser Guide Stars and a large Deformable Secondary Mirror. The latter will also be described as its use is optimum for GLAO systems. To cite this article: N. Hubin et al., C. R. Physique 6 (2005).     

Introduction to the physics of nucleation

In this introductory article, I review the theory of nucleation by thermal activation and by quantum tunneling. The effect of heterogeneous nucleation at surfaces is discussed and a brief survey of experimental techniques is given. To cite this article: H.J. Maris, C. R. Physique 7 (2006).     

De la microstructure du polymère à ses propriétés rhéologiquesFrom the microstructure of polymers towards their rheological properties

We extend the previous work by Benallal et al. on the relationship between structure and rheological properties of linear polymer melts. The aim of this paper is to quantify the effect of the chemical structure on the viscoelastic properties. We show that these properties are governed by the monomer dimensions and the interaction energy. To cite this article: A. Allal et al., C. R. Physique 3 (2002) 1451–1458.     

Modelling of long term kinetic evolution: a fruitful relationship between experiment and theoretical development

Recent developments in multi-scale modelling, based on atomic scale calculations, are leading to a growing conviction that modelling will soon be used to design material components for nuclear reactors. In this article we discuss this assumption on the basis of the relationship between experimental studies and theoretical calculations of the microstructural evolution of materials under irradiation. In the first part of the paper, the available numerical models for long term microstructural evolutions are briefly reviewed. The experimental methods are presented in a second part. In the third part, several examples of fruitful relationships between modelling and experiments are discussed. To cite this article: A. Barbu, C. R. Physique 9 (2008).     

Basic results in vacuum statistics

This is a review of recent work on constructing and finding statistics of string theory vacua, done in collaboration with Frederik Denef, Bogdan Florea, Bernard Shiffman and Steve Zelditch. To cite this article: M.R. Douglas, C. R. Physique 5 (2004).

Résumé

Cet article est une revue de travaux récents sur la construction et découverte de statistiques des vides de théories des cordes, réalisée en collaboration avec Frederik Denef, Bogdan Florea, Bernard Shiffman et Steve Zelditch. Pour citer cet article : M.R. Douglas, C. R. Physique 5 (2004).     

A review of X-ray intensity fluctuation spectroscopy

This article reviews the literature on X-ray fluctuation intensity spectroscopy or, as it is often called, X-ray photon correlation spectroscopy. It highlights measurements using different types of diffuse scattering. To cite this article: M. Sutton, C. R. Physique 9 (2008).     

X-rays and matter – the basic interactions

In this introductory article we attempt to provide the theoretical basis for developing the interaction between X-rays and matter, so that one can unravel properties of matter by interpretation of X-ray experiments on samples. We emphasize that we are dealing with the basics, which means that we shall limit ourselves to a discussion of the interaction of an X-ray photon with an isolated atom, or rather with a single electron in a Hartree–Fock atom. Subsequent articles in this issue deal with more complicated – and interesting – forms of matter encompassing many atoms or molecules. To cite this article: J. Als-Nielsen, C. R. Physique 9 (2008).     

Large intrinsic birefringence in zinc-blende based artificial semiconductors

A new attempt to solve the phase matching problem for semiconductor-based frequency conversion devices, based on the implementation of intrinsic birefringence in artificial materials, is discussed. The first results concerning the growth and characterization of ultrashort period superlattices are presented. To cite this article: J.-M. Jancu et al., C. R. Physique 8 (2007).