22,795 research outputs found

    Proton irradiation of e2v technologies L3Vision devices

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    This paper describes the proton irradiation and subsequent analysis of 8 e2v technologies CCD65 L3Vision devices with the intention of assessing the suitability of L3Vision technology to applications in space. In particular the use of L3Vision charge coupled devices (CCDs) on the Radial Velocity Spectrometer (RVS) instrument of the planned European Space Agency GAIA mission is discussed. The operational properties of the devices were characterised before irradiation with protons to a 10 MeV equivalent fluence of 2.5 × 109 protons cm-2. The devices were then characterised again before undergoing a second proton irradiation which increased the total 10 MeV equivalent proton fluence received by each device to 2.1 × 1010 protons cm-2. All 8 devices functioned as expected after each irradiation, with no catastrophic failures occurring even after the second irradiation which increased the total proton fluence to approximately 10 times the expected 6 year RVS fluence

    The correlation between RAE ratings and citation counts in psychology

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    We counted the citations received in one year (1998) by each staff member in each of 38 university psychology departments in the United Kingdom. We then averaged these counts across individuals within each department and correlated the averages with the Research Assessment Exercise (RAE) grades awarded to the same departments in 1996 and 2001. The correlations were extremely high (up to +0.91). This suggests that whatever the merits and demerits of the RAE process and citation counting as methods of evaluating research quality, the two approaches measure broadly the same thing. Since citation counting is both more cost-effective and more transparent than the present system and gives similar results, there is a prima facie case for incorporating citation counts into the process, either alone or in conjunction with other measures. Some of the limitations of citation counting are discussed and some methods for minimising these are proposed. Many of the factors that dictate caution in judging individuals by their citations tend to average out when whole departments are compared

    Proton induced leakage current in CCDs

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    The effect of different proton fluences on the performance of two E2V Technologies CCD47-20 devices was investigated with particular emphasis given to the analysis of 'random telegraph signal' (RTS) generation, bright pixel generation and induced changes in base dark current level. The results show that bright pixel frequency increases as the mean energy of the proton beam is increased, and that the base dark current level after irradiation scales with the level of ionization damage. For the RTS study, 500 pixels on one device were monitored over a twelve hour period. This data set revealed a number of distinct types of pixel change level fluctuation and a system of classification has been devised. Previously published RTS data is discussed and reviewed in light of the new data

    Nonmethane hydrocarbon and halocarbon distributions during Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange, June 1992

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    Aircraft measurements of selected nonmethane hydrocarbon and halocarbon species were made in the lower troposphere of the NE Atlantic near the Azores, Portugal, during June 1992 as part of the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange. In this paper, the impact of continental outflow from both Europe and North America on the study region were assessed. Four main air mass types were characterized from trajectories and trace gas concentrations: clean marine from the Atlantic, and continental air from the Iberian Peninsula, the British Isles and Northern Europe, and North America. Each classification exhibited trace gas concentrations that had been modified en route by photochemical processes and mixing. Comparison with the clean marine boundary layer (MBL) shows that the boundary layer of the predominantly continental air masses were enhanced in hydrocarbons and halocarbons by factors of approximately 2 for ethane, 5 for propane, 2-6 for ethyne and benzene, and 2-3 for C2Cl4. The same air masses also exhibited large ozone enhancements, with 2 to 3 times higher mixing ratios in the continental boundary layer air compared to the clean MBL. This indicates a primarily anthropogenic photochemical source for a significant fraction of the lower tropospheric ozone in this region. Methyl bromide exhibited on average 10-20% higher concentrations in the boundary layer affected by continental outflow than in the clean MBL, and was seen to be enhanced in individual plumes of air of continental origin. This is consistent with significant anthropogenic sources for methyl bromide. In addition, median MBL concentrations of ethene and methyl iodide showed enhancements of approximately a factor of 2 above free tropospheric values, suggesting primarily coastal/oceanic sources for these species. Copyright 1996 by the American Geophysical Union
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