9 research outputs found

    The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy

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    The CAT (Cherenkov Array at Themis) imaging telescope, equipped with a very-high-definition camera (546 fast phototubes with 0.12 degrees spacing surrounded by 54 larger tubes in two guard rings) started operation in Autumn 1996 on the site of the former solar plant Themis (France). Using the atmospheric Cherenkov technique, it detects and identifies very high energy gamma-rays in the range 250 GeV to a few tens of TeV. The instrument, which has detected three sources (Crab nebula, Mrk 421 and Mrk 501), is described in detail.Comment: 24 pages, 15 figures. submitted to Elsevier Preprin

    Analyse combinée FluoX-caméra RVB et FluoX-DRX des gisements de latérite nickélifÚre de Nouvelle-Calédonie : nouvelle approche méthodique

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    International audienceAs part of the European SOLSA project, BRGM and CRISMAT are participating in the development of a multi-sensor expertise bench (SOLSA ID2A-ID2B). The major challenge of SOLSA is to understand the approach of a field geologist to samples in order to enable the retranscription of his knowledge in the form of intelligent algorithms. In this context, a sample prepared in three forms (powder, thin slide and raw sample) was selected in this study. It is a serpentinised harzburgite. The sample was first characterised in the laboratory (X-ray fluorescence, ICP-AES, and X-ray diffraction) and then analysed under these different preparations on SOLSA ID2B. This study showed that the field approach allows similar results to those obtained in the laboratory but with a higher profitability. By comparing the results obtained on the three types of preparation, it was shown that the influence of the sample preparation is minor on the combined FluoX-DRX results. Finally, by creating an algorithm allowing the superposition of RGB images and the spatial distribution of chemical elements (Fig 1), it was possible to improve the knowledge of substitutions within the phases present, the location of certain elements in preferential zones and the element/element and phase/element correlations.Dans le cadre du projet europĂ©en SOLSA, le BRGM et le CRISMAT, participent au dĂ©veloppement d’un banc d’expertise multi-capteurs (SOLSA ID2A-ID2B). L’enjeu majeur de SOLSA, est d’apprĂ©hender l’approche d’un gĂ©ologue de terrain sur des Ă©chantillons afin de permettre une retranscription de son savoir sous forme d’algorithmes intelligents. Dans ce contexte, un Ă©chantillon prĂ©parĂ© sous trois formes (poudre, lame mince et Ă©chantillon brut) a Ă©tĂ© sĂ©lectionnĂ© dans cette Ă©tude. Il s’agit d’une harzburgite serpentinisĂ©e. L’échantillon a d’abord Ă©tĂ© caractĂ©risĂ© en laboratoire (fluorescence X, ICP-AES, et diffraction des rayons X) puis analysĂ© sous ces diffĂ©rentes prĂ©parations sur SOLSA ID2B. Cette Ă©tude a permis de montrer que l’approche de terrain admet des rĂ©sultats similaires aux rĂ©sultats obtenus en laboratoire mais avec une rentabilitĂ© plus Ă©levĂ©e. En comparant les rĂ©sultats obtenus sur les trois types de prĂ©paration, il a Ă©tĂ© dĂ©montrĂ© que l’influence de la prĂ©paration de l’échantillon est mineure sur les rĂ©sultats combinĂ©s FluoX-DRX. Enfin, par la crĂ©ation d’algorithme permettant la superposition d’image RVB et la distribution spatiale des Ă©lĂ©ments chimiques (Fig 1), il a Ă©tĂ© possible d’amĂ©liorer la connaissance des substitutions au sein des phases prĂ©sentes, la localisation de certains Ă©lĂ©ments dans des zones prĂ©fĂ©rentielles et les corrĂ©lations Ă©lĂ©ments/Ă©lĂ©ments et phases/Ă©lĂ©ments

    The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy

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    The CAT (Cherenkov Array at Th'emis) imaging telescope, equipped with a veryhigh -definition camera (546 fast phototubes with 0:12 ffi spacing surrounded by 54 Preprint submitted to Elsevier Preprint 31 March larger tubes in two guard rings) started operation in Autumn 1996 on the site of the former solar plant Th'emis (France). Using the atmospheric Cherenkov technique, it detects and identifies very high energy fl-rays in the range 250 GeV to a few tens of TeV. The instrument, which has detected three sources (Crab nebula, Markarian 421 and Markarian 501), is described in detail. Key words: Gamma-Ray Astronomy, Atmospheric Cherenkov detector 1 Introduction The recent development of Very-High-Energy Gamma-Ray Astronomy is essentially due to Atmospheric Cherenkov Telescopes (ACT). Since 1988, two arrays of Cherenkov detectors, ASGAT [1] and THEMISTOCLE [2] have been operated on the site of the former solar plant "Th'emis", close to Font-Romeu in the French Pyrenees. They consist of..

    Analyse combinée FluoX-caméra RVB et FluoX-DRX des gisements de latérite nickélifÚre de Nouvelle-Calédonie : nouvelle approche méthodique

    No full text
    International audienceAs part of the European SOLSA project, BRGM and CRISMAT are participating in the development of a multi-sensor expertise bench (SOLSA ID2A-ID2B). The major challenge of SOLSA is to understand the approach of a field geologist to samples in order to enable the retranscription of his knowledge in the form of intelligent algorithms. In this context, a sample prepared in three forms (powder, thin slide and raw sample) was selected in this study. It is a serpentinised harzburgite. The sample was first characterised in the laboratory (X-ray fluorescence, ICP-AES, and X-ray diffraction) and then analysed under these different preparations on SOLSA ID2B. This study showed that the field approach allows similar results to those obtained in the laboratory but with a higher profitability. By comparing the results obtained on the three types of preparation, it was shown that the influence of the sample preparation is minor on the combined FluoX-DRX results. Finally, by creating an algorithm allowing the superposition of RGB images and the spatial distribution of chemical elements (Fig 1), it was possible to improve the knowledge of substitutions within the phases present, the location of certain elements in preferential zones and the element/element and phase/element correlations.Dans le cadre du projet europĂ©en SOLSA, le BRGM et le CRISMAT, participent au dĂ©veloppement d’un banc d’expertise multi-capteurs (SOLSA ID2A-ID2B). L’enjeu majeur de SOLSA, est d’apprĂ©hender l’approche d’un gĂ©ologue de terrain sur des Ă©chantillons afin de permettre une retranscription de son savoir sous forme d’algorithmes intelligents. Dans ce contexte, un Ă©chantillon prĂ©parĂ© sous trois formes (poudre, lame mince et Ă©chantillon brut) a Ă©tĂ© sĂ©lectionnĂ© dans cette Ă©tude. Il s’agit d’une harzburgite serpentinisĂ©e. L’échantillon a d’abord Ă©tĂ© caractĂ©risĂ© en laboratoire (fluorescence X, ICP-AES, et diffraction des rayons X) puis analysĂ© sous ces diffĂ©rentes prĂ©parations sur SOLSA ID2B. Cette Ă©tude a permis de montrer que l’approche de terrain admet des rĂ©sultats similaires aux rĂ©sultats obtenus en laboratoire mais avec une rentabilitĂ© plus Ă©levĂ©e. En comparant les rĂ©sultats obtenus sur les trois types de prĂ©paration, il a Ă©tĂ© dĂ©montrĂ© que l’influence de la prĂ©paration de l’échantillon est mineure sur les rĂ©sultats combinĂ©s FluoX-DRX. Enfin, par la crĂ©ation d’algorithme permettant la superposition d’image RVB et la distribution spatiale des Ă©lĂ©ments chimiques (Fig 1), il a Ă©tĂ© possible d’amĂ©liorer la connaissance des substitutions au sein des phases prĂ©sentes, la localisation de certains Ă©lĂ©ments dans des zones prĂ©fĂ©rentielles et les corrĂ©lations Ă©lĂ©ments/Ă©lĂ©ments et phases/Ă©lĂ©ments

    Increasing exploration efficiency with SOLSA Expert System

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    SOLSA is the first automated expert system for on-site cores analysis. The scope is to provide a prototype to be an innovative and necessary tool for geo-metallurgy, in order to optimize the valorization of the ore. The Expert System consists in the combination of an integrated drilling rig providing cores of high quality, an automated scanner and phase identification software, developed for nickel laterites and bauxites but usable as well in other sectors. SOLSA combines non-destructive sensors and the whole system is driven by an innovative, user-friendly and intelligent software. SOLSA provides more complete information while optimizing the exploration stage, with a significant reduction of costs and return time. Such objective involves, in the first place, to fast, cheaper and systematic acquisition of the data needed for optimizing the process. The adding value takes place first at the exploration or grade control stage, furnishing systematic characterization and regionalization of the different types of ore. Then such information can be used for improving the ore scheduling at the mining and processing stages, toward improving the recovery and efficiency of the processin

    Spectrum of TeV gamma-rays from the Crab Nebula by the CAT Cherenkov Imaging Telescope

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    For an anthropology of communication What do we mean by “anthropology of communication”? The term is used for the ethnographic analysis of human communication as well as for behavioural changes due to the application of new information technologies. We put forward an introduction (below), to be followed by seven texts: three reflections on “anthropology”, three on “communication” and one concerned with the overlap between these two concepts. Starting with December 2004, these papers will be accessible at the rate of one paper a month. Our intention is to search for all terms associated with “anthropology” and “communication”, to create an inventory of representative semantic fields for them, to indicate current overlaps established by colleagues carrying out communications and information research as well as possible overlaps in the future

    Spectrum of TeV gamma-rays from the Crab Nebula by the CAT Cherenkov Imaging Telescope

    No full text
    For an anthropology of communication What do we mean by “anthropology of communication”? The term is used for the ethnographic analysis of human communication as well as for behavioural changes due to the application of new information technologies. We put forward an introduction (below), to be followed by seven texts: three reflections on “anthropology”, three on “communication” and one concerned with the overlap between these two concepts. Starting with December 2004, these papers will be accessible at the rate of one paper a month. Our intention is to search for all terms associated with “anthropology” and “communication”, to create an inventory of representative semantic fields for them, to indicate current overlaps established by colleagues carrying out communications and information research as well as possible overlaps in the future
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