Rapport final de la Collaboration CERN-CNRS pour la construction du LHC: Accord Technique d'Exécution No 2 Cryostats et assemblage des sections droites courtes (SSS) du LHC

Depuis 1995 et suite à la signature du protocole de Collaboration, le CERN, le CEA et le CNRS ont étroitement collaboré dans le cadre de la contribution exceptionnelle de la France à la construction du LHC. Pour le CNRS, l'Institut de Physique Nucléaire d'Orsay a pris en charge deux Accords Techniques d'Exécution. Le premier concerne la conception et l'assemblage des Sections Droites Courtes de la machine, et le deuxième, l'étalonnage des thermomètres cryogéniques du LHC. Dans le cadre de l'Accord Technique d'Exécution N°2, le Bureau d'Etudes de la Division Accélérateur de l'IPNO et le groupe AT-CRI du CERN ont travaillé de concert pour mener à bien la conception des SSS (Short Straight Section) et de tous les équipements nécessaires à l'assemblage. Ce rapport a donc pour objectif de dresser, en termes d'historique, d'organisation, de résultats quantitatifs et qualitatifs et de moyens mis en ?uvre, un tableau aussi complet que possible du déroulement de cette Collaboration entre le CERN et le CNRS

Thermal Performance of the LHC Short Straight Section Cryostat

The LHC Short Straight Section (SSS) cryostat houses and thermally protects in vacuum the cold mass which contains a twin-aperture superconducting quadrupole magnet and superconducting corrector magnets operating at 1.9 K in superfluid helium. In addition to mechanical requirements, the cryostat is designed to minimize the heat in-leak from the ambient temperature to the cold mass. Mechanical components linking the cold mass to the vacuum vessel such as support posts and an insulation vacuum barrier are designed to have minimum heat conductivity with efficient thermalisations for heat interception. Heat in-leak by radiation is reduced by employing multilayer insulation wrapped around the cold mass and an actively cooled aluminium thermal shield. The recent commissioning and operation of two SSS prototypes in the LHC Test String 2 have given a first experimental validation of the thermal performance of the SSS cryostat in nominal operating conditions. Temperature sensors mounted in critical locations provide a temperature mapping which allows a crosscheck with the calculated temperature values and thermal performance. Moreover the measurements allowed a validation of the efficiency of the employed thermalisations. This paper presents the experimental results for the thermal performance of cryostat components and gives a first comparison with the design values

Photoinduced refractive-index changes in germanosilicate fibres

Photoinduced guided index changes approaching 10-4 in the range 488-784 nm, measured using a simple interferometric technique, are reported in germanosilicate single-mode optical fibers exposed to the 488-nm line of an Ar+ laser running multifrequency. The wavelength dependence and dynamics of the writing process are characterized, and the material dispersion of the induced Δn(λ) is shown to be weak. The effect is placed in the context of related research on color centers in these fibers, and two different mechanisms are proposed that lead to quantitative estimates in rough agreement with the measured Δn values

Multimedia delivery in the future internet

The term “Networked Media” implies that all kinds of media including text, image, 3D graphics, audio and video are produced, distributed, shared, managed and consumed on-line through various networks, like the Internet, Fiber, WiFi, WiMAX, GPRS, 3G and so on, in a convergent manner [1]. This white paper is the contribution of the Media Delivery Platform (MDP) cluster and aims to cover the Networked challenges of the Networked Media in the transition to the Future of the Internet. Internet has evolved and changed the way we work and live. End users of the Internet have been confronted with a bewildering range of media, services and applications and of technological innovations concerning media formats, wireless networks, terminal types and capabilities. And there is little evidence that the pace of this innovation is slowing. Today, over one billion of users access the Internet on regular basis, more than 100 million users have downloaded at least one (multi)media file and over 47 millions of them do so regularly, searching in more than 160 Exabytes1 of content. In the near future these numbers are expected to exponentially rise. It is expected that the Internet content will be increased by at least a factor of 6, rising to more than 990 Exabytes before 2012, fuelled mainly by the users themselves. Moreover, it is envisaged that in a near- to mid-term future, the Internet will provide the means to share and distribute (new) multimedia content and services with superior quality and striking flexibility, in a trusted and personalized way, improving citizens’ quality of life, working conditions, edutainment and safety. In this evolving environment, new transport protocols, new multimedia encoding schemes, cross-layer inthe network adaptation, machine-to-machine communication (including RFIDs), rich 3D content as well as community networks and the use of peer-to-peer (P2P) overlays are expected to generate new models of interaction and cooperation, and be able to support enhanced perceived quality-of-experience (PQoE) and innovative applications “on the move”, like virtual collaboration environments, personalised services/ media, virtual sport groups, on-line gaming, edutainment. In this context, the interaction with content combined with interactive/multimedia search capabilities across distributed repositories, opportunistic P2P networks and the dynamic adaptation to the characteristics of diverse mobile terminals are expected to contribute towards such a vision. Based on work that has taken place in a number of EC co-funded projects, in Framework Program 6 (FP6) and Framework Program 7 (FP7), a group of experts and technology visionaries have voluntarily contributed in this white paper aiming to describe the status, the state-of-the art, the challenges and the way ahead in the area of Content Aware media delivery platforms

A Modular Design for the 56 Variants of the Short Straight Section in the Arcs of the Large Hadron Collider (LHC)

The 360 Short Straight Sections (SSS) necessary for the eight arcs of the LHC machine have to fulfil different requirements. Their main function is to house the lattice two-in-one superconducting quadrupole and various correction magnets, all operating at 1.9 K in a superfluid helium bath. The magnetic and powering schemes of the arcs and the fact that the two proton beams alternate between the inner and outer magnet channels impose 24 different combinations of magnet assemblies, all housed in an identical helium enclosure. The cryogenic architecture of the LHC machine is based on cryogenic loops spanning over one half-cell (53 m) for the 4.6-20 K circuit, over a full cell (107 m) for the 1.9 K circuits, up to the full arc (about 2.3 km) for the shield cooling line. This cryogenic layout, when superimposed to the magnetic scheme, further complicated by the cryostat insulation vacuum sectorisation every 2 cells, creates additional assembly variants, up to a total number of 56. The required flexibility in the manufacture and assembly, as well as economic considerations, have led to a modular design for the different SSS components and sub-assemblies. This modularity allows to "specialise" the SSS at the latest possible assembly step of the "just in time" production line. This paper presents the conceptual design considerations to achieve this modularity, the SSS design retained for the series manufacture, and the assembly procedures recently validated on a prototype program at CERN

Déterminisme génétique du nombre de cæca pyloriques chez la Truite fario (Salmo Trutta, Linné) et la Truite arc-en-ciel (Salmo Gairdneri, Richardson) III. — Effet du génotype et de la taille des æufs sur la réalisation du caractère chez la Truite fario

International audienceAn analysis of the variation of the number of pyloric caeca in hatchery-reared brown trout showed that :- the sex of the animals has no significant influence;- an important part of variability is caused by additive genetic factors (approximate heritability 0.4);[br/]- there is a maternal effect which inheres to the size of eggs; alevins hatched from large eggs tend to have high numbers of caeca (correlation + 0,5)- lastly, the joined action of that maternal factor and other genetic and environmental factors apparently includes interactive effects; further studies on that point would be useful.L'analyse de la variation du nombre de caeca pyloriques chez la Truite fario élevée en pisciculture a montré que :- le sexe des animaux n'a aucune influence significative;- une part importante de variabilité est d'origine génétique additive (héritabilité approximative 0,4);- il existe un effet maternel inhérent à la taille des oeufs, les alevins issus de gros aeufs tendant à avoir des nombres de caeca élevés (corrélation +0,5);- enfin, l'action conjointe de ce facteur maternel et des autres facteurs génétiques et environnementaux semble comporter des effets interactifs dont l'étude plus approfondie serait utile

High second-order nonlinearities in poled silicate fibers

Effective quadratic nonlinearities are high as 0.2 pm/V are reported for the first time to our knowledge in poled germanosilicate fibers. This value is ~200 time higher than previously achieved in these fibres. The presence of Ge is found to enhance the efficacy of both thermal (in combination with OH doping) and electron-beam poling in silica

High second-order nonlinearities induced in lead-silicate glass by electron-beam irradiation

A new technique for inducing a large permanent second-order susceptibility in lead silicate glass is reported. The procedure involves implanting electrons by irradiating the glass with an electron beam. Second-order nonlinearities χ(2) as high as 0.7 pm/V are obtained