26 research outputs found

    HARPO: a TPC as a gamma-ray telescope and polarimeter

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    A gas Time Projection Chamber can be used for gamma-ray astronomy with excellent angular-precision and sensitivity to faint sources, and for polarimetry, through the measurement of photon conversion to e+e−e^+e^- pairs. We present the expected performance in simulations and the recent development of a demonstrator for tests in a polarized photon beam.Comment: SPIE Astronomical Telescopes + Instrumentation, Ultraviolet to gamma ray, Montr\'eal, Canada 2014. v2: note added in proof. Copyright 2014 SPIE. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibite

    Otimização adaptativa de um campo de poços vulneråvel

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    International audienceThe contamination of groundwater resources is a challenge for drinking water supplies. To meet water quality standards, well-field operators need practical solutions to reduce the vulnerability of production wells. Strategies for several combinations ofmanagement variables such as well flow rate or water level in drains, are usually possible to satisfy the required production rate.However, these strategies may lead to contamination issues for the abstracted groundwater. A surrogate transport model wasimplemented in a well field vulnerable to a contaminated stream. An adaptive multi-objective optimization approach is proposed.The objective is to maximize the water production at the well field while minimizing the proportion of stream water abstracted.The optimization problem is adaptive to the stream level, which is a key parameter describing hydrological conditions. Asystematic exploration of management settings is conducted and a three-dimensional Pareto front is extracted. From theseoptimum settings, a practical easy-to-use approach is developed. The well-field operator can adjust production settings tooptimum conditions as a function of the observed stream water level and desired production rate.La contamination de la ressource en eaux souterraine est un dĂ©fi pour l’approvisionnement en eau potable. Pour respecter les normes de qualitĂ© de l’eau potable, les exploitants ont besoin de solutions pratiques pour rĂ©duire la vulnĂ©rabilitĂ© des puits de production. La mise en place de stratĂ©gies jouant sur les schĂ©mas de gestion, telles que le dĂ©bit des puits ou le niveau d’eau dans les drains, sont gĂ©nĂ©ralement possibles pour atteindre le dĂ©bit de production requis. Cependant, ces stratĂ©gies peuvent entraĂźner des problĂšmes de contamination des eaux souterraines captĂ©es. Un modĂšle Ă©quivalent de transport a Ă©tĂ© mis en Ɠuvre sur un champ captant vulnĂ©rable Ă  un cours d’eau contaminĂ©. Une approche d’optimisation multi-objectifs adaptative est proposĂ©e. L’objectif est de maximiser la production d’eau tout en minimisant la proportion d’eau du cours d’eau captĂ©e. Le problĂšme d’optimisation est adaptatif au niveau du cours d’eau, paramĂštre clĂ© dĂ©crivant les conditions hydrologiques. Une exploration systĂ©matique des paramĂštres de gestion est effectuĂ©e et un front de Pareto tridimensionnel est extrait. À partir de ces paramĂštres optimaux, une approche pratique et facile Ă  utiliser est dĂ©veloppĂ©e. L’opĂ©rateur peut ajuster les paramĂštres de production aux conditions optimales en fonction du niveau d’eau du cours d’eau observĂ© et du dĂ©bit de production souhaitĂ©

    Neutron detection and application with a novel 3D-projection scintillator tracker in the future long-baseline neutrino oscillation experiments

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    Neutrino oscillation experiments require a precise measurement of the neutrino energy. However, the kinematic detection of the final-state neutron in the neutrino interaction is missing in current neutrino oscillation experiments. The missing neutron kinematic detection results in a smaller detected neutrino energy than the true neutrino energy. A novel 3D-projection scintillator tracker, which consists of roughly ten million active cubes covered with an optical reflector, is capable of measuring the neutron kinetic energy and direction on an event-by-event basis using the time-of-flight technique thanks to the fast timing, fine granularity, and high light yield. The ÎœÂŻÎŒ interactions tend to produce neutrons in the final state. By measuring the neutron kinetic energy, the ÎœÂŻÎŒ energy can be reconstructed better, allowing a tighter incoming neutrino flux constraint. This article shows the detector's ability to reconstruct neutron kinetic energy and the ÎœÂŻÎŒ flux constraint achieved by selecting the charged-current interactions without mesons or protons in the final state.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236

    Electronics for HARPO: Design, development and validation of electronics for a high performance polarised-Gamma-ray detector

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    International audienceWe designed and built an experimental apparatus based on a time projection chamber, a novel scheme for high performance γ-ray astronomy and polarimetry in the γ → e+e- regime. This presentation focuses on the electronics aspect of the detector and, in particular, on the versatile dedicated trigger system that we have developed which allowed us to take data on beam with a high γ-conversion signal efficiency and a high rejection factor for single tracks and upstream conversion background events. Our scheme allows for the selective collection of γ conversions in a high-background-rate environment, such as that which is present in orbit, with a fine 3D imaging of the events and very low (in particular electronics) background, at a mild cost in terms of the number of electronics channels and therefore of electrical power consumption

    A transition support system to build decarbonization scenarios in the academic community

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    International audienceA growing portion of scientists realises the need to not only alert about climate change, but also change their professional practices. A range of tools have emerged to promote more sustainable activities, yet many scientists struggle to go beyond simple awareness-raising to create concrete transition actions. Here we propose a game-based transition support system MaTerre180’ , which has been designed to build scenarios of greenhouse gas (GHG) emission reductions in the academic community. After providing a common scientific background about the context (global warming issue, its causes and consequences) and setting up a challenge (50% reduction of carbon budget by 2030), the participants belonging to the academic community and its governance bodies immerse themselves into fictional characters, to simulate the behaviour of real research groups. The game has been deployed during the year 2021, with six hundred participants from nine countries and 50 cities. Results explore clear pathways for GHG reductions between 25 and 60%, and a median reduction of 46%. The alternatives allowing the greatest reduction are video communication tools (36%), followed by mutualization of professional activities and voluntary cancellation or reduction, that represent 22 and 14% of reduction, respectively. The remaining 28% of reduction consists of transport alternative, relocation of professional activities, extended duration of some travels, etc. In addition, the analyses pointed out the importance of the guided negotiation phase to bring out some alternatives such as relocation, local partners and computing optimization. An added value of this transition support system is that the information it collects (anonymously) will be used to answer pressing research questions in climate change science and environmental psychology regarding the use of serious games for promoting changes in attitudes and behaviours towards sustainability, and including broader questions on how network structures influence “climate behaviour”, knowledge and the governance of the commons. Modestly, MaTerre180’ offers an innovative game-based transition support system to build scenarios of greenhouse gas (GHG) emission reductions in the academic community. It is not simply a question of moving tokens on a virtual gameboard and a playful adjustment of practices, but rather a question of brainstorming about possible and desirable ways of remodelling research and teaching communities and embracing a new paradigm. After tens of workshops, our results show clear pathways for reaching up to 50% GHG reductions and stress the importance of guided negotiations to bring out alternatives to carbonized activities. This first attempt reinforces our belief that scientific engagement is at the heart of the international development agenda and a key approach to tear down the institutional barriers that inhibit the transformation needed to achieve a more sustainable society
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