Recent Progress on Correcting Components (useful for ELTs) at CILAS

Recent progresses on correcting components at CILAS are exposed: the first one is relative to a 3.5 mm spacing, 28x28 order demonstrator for small pitch concave or convex deformable mirrors designed, manufactured and tested in the scope of feasibility study for the E-ELT MCAO module. The second one is relative to a 1 mm spacing, 50x50 order deformable mirror prototype. This prototyping allows the validation of some main important steps of manufacturing very high order deformable mirrors. This new piezo array family called “miniDM” uses transverse piezo-electrical effect. The last one is relative to a Tip/Tilt Mount prototype that has been designed and manufactured for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the MCAO system of the TMT. The system shows large angular stroke and bandwidth while supporting a heavy deformable mirror

Active control of a large deformable mirror for future E-ELT

International audienceIncreasing dimensions of ground based telescopes and adaptive optics needs for these instruments require wide deformable mirrors with a high number of actuators to compensate the effects of the atmospheric turbulence on the wave fronts. The new dimensions and characteristics of these deformable mirrors lead to the apparition of structural vibrations, which may reduce the rejection band width of the adaptive optics control loop. The aim of this paper is the study of the dynamic behavior of a 1-meter prototype of E-ELT's deformable mirror in order to identify its eigenmodes and to propose some ways to control its vibrations. We first present the first eigenmodes of the structure determined by both finite element analysis and experimental modal analysis. Then we present the frequency response of the prototype to a tilt excitation to estimate the effects of its vibrations on the adaptive optics loop. Finally we suggest a method to control the dynamics of the deformable mirror

Modeling of a large deformable mirror for future E-ELT

International audienceIncreasing dimensions of ground based telescopes while implementing Adaptive Optics systems to cancel both structural deformations and atmospheric effects require very large diameters deformable mirrors (DM) and a high number of actuators with large strokes. This has led for the future E-ELT to a 2.5 m diameter DM getting about 8000 actuators. This paper presents a local and a global model of the DM in order to both study its influence function and its dynamical behavior. In the first part, influence function of the mirror is calculated. Results obtained by an analytical way are compared to those obtained numerically. In the second part, modal analysis of the mirror is presented. Results are limited to the first modes. Modal analysis is also only made for the base plate to derive the specific influence of DM's components on the global dynamic behavior. In the last part, optimization methods are used to help designing a 1 m prototype of the DM

A system dynamics model for the management of the Manila clam, Ruditapes philippinarum (Adams & Reeve, 1850) in the Bay of Arcachon (France)

The Manila clam Ruditapes philippinarum (Adams and Reeve, 1850) is one of the mollusc species that, driven mainly by the shellfish market industry, has extended throughout the world, far beyond the limits of its original habitat. The Manila clam was introduced into France for aquaculture purposes, between 1972 and 1975. In France, this venerid culture became increasingly widespread and, since 1988, this species has colonised most of the embayments along the French Atlantic coast. In 2004, this development resulted in a fishery of ca. 520 t in Arcachon Bay

Síntese e estudo microestrutural de perovsquitas tipo La0,8Ca0,2MO3 (M: Co e Mn) para aplicação em catálise automotiva Synthesis and microstructural study of La0.8Ca0.2MO3 (M: Mn and Co) perovskites for automotive catalysis

Materiais com estrutura perovsquita são potenciais catalisadores para prevenir a emissão de componentes indesejáveis ao meio ambiente. Diferentes métodos têm sido propostos para a síntese desses materiais, visando produzir materiais homogêneos com tamanho nanométrico de partículas. Os compostos La0,8Ca0,2MnO3 e La0,8Ca0,2CoO3 foram preparados pelo método dos precursores poliméricos visando sua utilização como catalisadores automotivos. Este método de síntese foi utilizado porque permite a obtenção de pós homogêneos e fases cristalinas a temperaturas mais baixas que os outros métodos tradicionais de síntese. Os materiais foram calcinados a 700 e 900 ºC por 4 h e caracterizados pelas técnicas de análise térmica, difração de raios X e microscopia eletrônica de varredura. As perovsquitas obtidas são nanométricas, monofásicas e com propriedades adequadas para utilização em catálise automotiva.<br>Materials with perovskite structure are potential catalysts for preventing greenhouse gas emissions to the environment. Several methods have been proposed for the synthesis of these materials in order to produce homogeneous powders with nanometric particle size. In the present work, the La0.8Ca0.2MnO3 and La0.8Ca0.2CoO3 systems were prepared by the polymeric precursor method for application in automotive catalysis. This method was chosen because it allows obtaining homogeneous powders and crystalline phases at lower temperatures. The powders were calcined at 700 and 900 ºC for 4 h and characterized by thermal analysis, X-ray diffraction and scanning electron microscopy techniques. The perovskites are nanometric, single phased and present suitable properties for use in automotive catalysis

Last progress concerning the design of the piezo stack M4 adaptive unit of the E-ELT

International audienceCILAS proposes a M4 adaptive mirror (M4AM) that corrects the atmospheric turbulence at high frequencies and residual tip-tilt and defocus due to telescope vibrations by using piezostack actuators. The design presents a matrix of 7217 actuators (triangular geometry, spacing equal to 29 mm) leading to a fitting error reaching the goal. The mirror is held by a positioning system which ensures all movements of the mirror at low frequency and selects the focus (Nasmyth A or B) using a hexapod concept. This subsystem is fixed rigidly to the mounting system and permits mirror displacements. The M4 control system (M4CS) ensures the connection between the telescope control/monitoring system and the M4 unit - positioning system (M4PS) and piezostack actuators of the M4AM in particular. This subsystem is composed of electronic boards, mechanical support fixed to the mounting structure and the thermal hardware. With piezostack actuators, most of the thermal load is minimized and dissipated in the electronic boards and not in the adaptive mirror. The mounting structure (M4MS) is the mechanical interface with the telescope (and the ARU in particular) and ensures the integrity and stability of M4 unit subsystems. M4 positioning system and mounting structure are subcontracted to AMOS company