5,925 research outputs found

    Commissioning of the ATLAS Level-1 Trigger with Cosmic Rays

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    The ATLAS detector at CERN's Large Hadron Collider will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system was designed to select potentially interesting events and reduce the incoming rate to 100-200 Hz. The first trigger level (LVL1) is implemented in custom-built electronics, the second and third trigger levels are realized in software. Based on calorimeter information and hits in dedicated muon-trigger detectors, the LVL1 decision is made by the central-trigger processor yielding an output rate of less than 100 kHz. The allowed latency for the trigger decision at this stage is less than 2.5 microseconds. Installation of the final LVL1 trigger system at the ATLAS site is in full swing, to be completed later this year. We present a status report of the main components of the first-level trigger and the in-situ commissioning of the full trigger chain with cosmic-ray muons.Comment: On behalf of the ATLAS TDAQ Level-1 Trigger Group. Proceedings for 2007 Europhysics Conference on High Energy Physics, Manchester, July 200

    Growth, mortality and recruitment of commercially important fishes and penaeid shrimps in Indonesian waters

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    Population dynamics, Stock assessment, Commercial species, Shrimp fisheries, Arafura Sea, Indonesia, Penaeus merguiensis

    Effect of Application of Farmyard Manure to Ley on Forage Yield and Quality of Grass Silage

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    A two-year field trial was performed on ley near Uppsala, Sweden, with the following treatments (3 plots/treatment): A, no manure or fertiliser; B, manure applied in Oct.; C, manure applied in Oct. followed by rolling plots in May; D, manure applied in May; E, mineral fertiliser only. Apart from cattle manure, plots allocated to treatments B, C and D received the same amount of mineral nutrients as treatment E. The objective of this experiment was to get an indication of how different times of manure application (before or after the growth period) affected forage yields and the quality of the resulting silage. Annual forage yields (2 cuts/year) did not differ significantly in either year among treatments that received manure. Only the unfertilised control treatment (A) had a significantly lower yield. No differences were found between treatments that received only mineral fertilisers (E) or mineral fertilisers and manure (B, C and D). The 1998 ensiling experiment resulted in a very low overall silage quality, indicated by excessive formation of ammonia and very high counts of Clostridium spores (\u3e 106 cfu/g silage). In 1999, the best silage, with the lowest counts of Clostridium spores (\u3c 50 cfu/g), was produced from plots, which received manure in Oct. and were rolled in May (C). The same treatment without rolling in May (B) resulted in silage with a significantly higher pH, more butyric acid, and more Clostridium spores (\u3e 105 cfu/g). Other silage from manured plots, particularly that made from unchopped forage, also had high counts of Clostridium spores

    Laser powder bed fusion of a superelastic Cu-Al-Mn shape memory alloy

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    Dense and crack-free specimens of the shape memory alloy Cu71.6Al17Mn11.4 (at.%) were produced via laser powder bed fusion across a wide range of process parameters. The microstructure, viz. grain size, can be directly tailored within the process and with it the transformation temperatures (TTs) shifted to higher values by raising the energy input. The microstructure, and the superelastic behavior of additively manufactured samples were assessed by a detailed comparison with induction melted material. The precipitation of the α phase, which inhibit the martensitic transformation, were not observed in the additively manufactured samples owing to the high intrinsic cooling rates during the fabrication process. Fine columnar grains with a strong [001]-texture along the building direction lead to an enhanced yield strength compared to the coarse-grained cast samples. A maximum recoverable strain of 2.86% was observed after 5% compressive loading. The first results of our approach imply that laser powder bed fusion is a promising technique to directly produce individually designed Cu-Al-Mn shape memory parts with a pronounced superelasticity at room temperature

    The ATLAS beam pick-up based timing system

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    The ATLAS BPTX stations are comprised of electrostatic button pick-up detectors, located 175 m away along the beam pipe on both sides of ATLAS. The pick-ups are installed as a part of the LHC beam instrumentation and used by ATLAS for timing purposes. The usage of the BPTX signals in ATLAS is twofold: they are used both in the trigger system and for LHC beam monitoring. The BPTX signals are discriminated with a constant-fraction discriminator to provide a Level-1 trigger when a bunch passes through ATLAS. Furthermore, the BPTX detectors are used by a stand-alone monitoring system for the LHC bunches and timing signals. The BPTX monitoring system measures the phase between collisions and clock with a precision better than 100 ps in order to guarantee a stable phase relationship for optimal signal sampling in the subdetector front-end electronics. In addition to monitoring this phase, the properties of the individual bunches are measured and the structure of the beams is determined. On September 10, 2008, the first LHC beams reached the ATLAS experiment. During this period with beam, the ATLAS BPTX system was used extensively to time in the read-out of the sub-detectors. In this paper, we present the performance of the BPTX system and its measurements of the first LHC beams.Comment: 3 pages. Submitted to NIM A for the proceedings of TIPP09 (Tsukuba, Japan
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