| 1. |
- Aad, G., et al.
(författare)
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Readiness of the ATLAS Tile Calorimeter for LHC collisions
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:4, s. 1193-1236
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Tidskriftsartikel (refereegranskat)abstract
- The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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| 2. |
- Abat, E., et al.
(författare)
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Combined performance studies for electrons at the 2004 ATLAS combined test-beam
- 2010
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Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 5, s. P11006-
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Tidskriftsartikel (refereegranskat)abstract
- In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.
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| 3. |
- Abata, E., et al.
(författare)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
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Tidskriftsartikel (refereegranskat)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 6. |
- Alfonso, E., et al.
(författare)
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Design of microwave circuits in ridge gap waveguide technology
- 2010
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781424460564 ; , s. 1544 - 1547
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Konferensbidrag (refereegranskat)abstract
- This paper presents recent advances is a new waveguiding technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and submillimeter waves. In these waveguides there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high impedance (ideally a perfect magnetic conductor) through the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear within the band of operation. The paper studies the characteristic impedance of the line and presents simulations and measurements of circuits designed using this technology.
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| 7. |
- Alfonso, E., et al.
(författare)
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Power divider in ridge gap waveguide technology
- 2010
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Ingår i: EuCAP 2010 Fourth European Conference on Antennas and Propagation, Barcelona, 12-16 April 2010. - 9781424464319
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Konferensbidrag (refereegranskat)abstract
- A power divider in ridge gap waveguide technology has been designed to work at 15GHz. Measurements and simulations are provided. Besides, a broad numerical study of the characteristic impedance of a ridge gap waveguide is presented.
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| 8. |
- Gioiosa, Roberto, et al.
(författare)
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Designing OS for HPC applications: Scheduling
- 2010
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Ingår i: Proceedings - IEEE International Conference on Cluster Computing, ICCC. - 1552-5244. - 9780769542201 ; , s. 78-87
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Konferensbidrag (refereegranskat)abstract
- Operating systems have historically been implemented as independent layers between hardware and applications. User programs communicate with the OS through a set of well defined system calls, and do not have direct access to the hardware. The OS, in turn, communicates with the underlying architecture via control registers. Except for these interfaces, the three layers are practically oblivious to each other. While this structure improves portability and transparency, it may not deliver optimal performance. This is especially true for High Performance Computing (HPC) systems, where modern parallel applications and multi-core architectures pose new challenges in terms of performance, power consumption, and system utilization. The hardware, the OS, and the applications can no longer remain isolated, and instead should cooperate to deliver high performance with minimal power consumption. In this paper we present our experience with the design and implementation of High Performance Linux (HPL), an operating system designed to optimize the performance of HPC applications running on a state-of-the-art compute cluster. We show how characterizing parallel applications through hardware and software performance counters drives the design of the OS and how including knowledge about the architecture improves performance and efficiency. We perform experiments on a dual-socket IBM POWER6 machine, showing performance improvements and stability (performance variation of 2.11% on average) for NAS, a widely used parallel benchmark suite.
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| 9. |
- Olsen, J. L., et al.
(författare)
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The phylogeographic architecture of the fucoid seaweed Ascophyllum nodosum: an intertidal 'marine tree' and survivor of more than one glacial-interglacial cycle
- 2010
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 37:5, s. 842-856
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Tidskriftsartikel (refereegranskat)abstract
- Aim Ascophyllum nodosum (L.) Le Jolis is a dominant fucoid seaweed occurring along sheltered, rocky shores throughout the North Atlantic (but not in the Pacific), where it is a foundational species of the intertidal community. Its large size and vulnerability to ice-scour have led to the hypothesis that contemporary populations in the north-west Atlantic may be the result of de novo recolonization from the north-east Atlantic since the Last Glacial Maximum (LGM) (c. 20 ka). We tested this hypothesis. Location Temperate North Atlantic rocky intertidal between c. 42 and 65 degrees N latitude. Methods More than 1300 individuals from 28 populations were sampled from across the entire range of A. nodosum and genotyped for six microsatellite loci, and > 500 individuals were genotyped for two mitochondrial loci, an intergenic spacer (IGS) and the tRNA (W) gene (trnW). Population structure and historical demography were analysed in a standard population genetics and coalescence framework. Results Based on the presence of private alleles and haplotypes, we found that A. nodosum has survived on both sides of the Atlantic (since before the LGM, dating back to at least the penultimate Eemian interglacial) with similar effective population sizes and divergence times (1.2 and 0.8 Ma). Dispersal has been predominantly from Europe to North America, and there is very weak present-day population differentiation across the North Atlantic. Diversity measures provided additional support for determining the location of refugia. Main conclusions Ascophyllum nodosum was apparently little affected by the LGM, although contemporary climate change is likely to have major effects on its latitudinal distribution on both sides of the North Atlantic. It is a very long-lived species, analogous in virtually all demographic aspects to a tree - resistant to extinction but vulnerable to catastrophic events. The Brittany peninsula is a hotspot of genetic diversity worthy of conservation.
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