2,121 research outputs found
Optimization of thin n-in-p planar pixel modules for the ATLAS upgrade at HL-LHC
The ATLAS experiment will undergo around the year 2025 a replacement of the
tracker system in view of the high luminosity phase of the LHC (HL-LHC) with a
new 5-layer pixel system. Thin planar pixel sensors are promising candidates to
instrument the innermost region of the new pixel system, thanks to the reduced
contribution to the material budget and their high charge collection efficiency
after irradiation. The sensors of 50-150 m thickness, interconnected to
FE-I4 read-out chips, have been characterized with radioactive sources and beam
tests. In particular active edge sensors have been investigated. The
performance of two different versions of edge designs are compared: the first
with a bias ring, and the second one where only a floating guard ring has been
implemented. The hit efficiency at the edge has also been studied after
irradiation at a fluence of \neqcm. Highly segmented sensors will
represent a challenge for the tracking in the forward region of the pixel
system at HL-LHC. In order to reproduce the performance of 50x50 m
pixels at high pseudo-rapidity values, FE-I4 compatible planar pixel sensors
have been studied before and after irradiation in beam tests at high incidence
angles with respect to the short pixel direction. Results on the hit efficiency
in this configuration are discussed for different sensor thicknesses
Investigation of thin n-in-p planar pixel modules for the ATLAS upgrade
In view of the High Luminosity upgrade of the Large Hadron Collider (HL-LHC),
planned to start around 2023-2025, the ATLAS experiment will undergo a
replacement of the Inner Detector. A higher luminosity will imply higher
irradiation levels and hence will demand more ra- diation hardness especially
in the inner layers of the pixel system. The n-in-p silicon technology is a
promising candidate to instrument this region, also thanks to its
cost-effectiveness because it only requires a single sided processing in
contrast to the n-in-n pixel technology presently employed in the LHC
experiments. In addition, thin sensors were found to ensure radiation hardness
at high fluences. An overview is given of recent results obtained with not
irradiated and irradiated n-in-p planar pixel modules. The focus will be on
n-in-p planar pixel sensors with an active thickness of 100 and 150 um recently
produced at ADVACAM. To maximize the active area of the sensors, slim and
active edges are implemented. The performance of these modules is investigated
at beam tests and the results on edge efficiency will be shown
Performance of irradiated thin n-in-p planar pixel sensors for the ATLAS Inner Tracker upgrade
The ATLAS collaboration will replace its tracking detector with new all
silicon pixel and strip systems. This will allow to cope with the higher
radiation and occupancy levels expected after the 5-fold increase in the
luminosity of the LHC accelerator complex (HL-LHC). In the new tracking
detector (ITk) pixel modules with increased granularity will implement to
maintain the occupancy with a higher track density. In addition, both sensors
and read-out chips composing the hybrid modules will be produced employing more
radiation hard technologies with respect to the present pixel detector. Due to
their outstanding performance in terms of radiation hardness, thin n-in-p
sensors are promising candidates to instrument a section of the new pixel
system. Recently produced and developed sensors of new designs will be
presented. To test the sensors before interconnection to chips, a punch-through
biasing structure has been implemented. Its design has been optimized to
decrease the possible tracking efficiency losses observed. After irradiation,
they were caused by the punch-through biasing structure. A sensor compatible
with the ATLAS FE-I4 chip with a pixel size of 50x250 m,
subdivided into smaller pixel implants of 30x30 m size was
designed to investigate the performance of the 50x50 m
pixel cells foreseen for the HL-LHC. Results on sensor performance of 50x250
and 50x50 m pixel cells in terms of efficiency, charge
collection and electric field properties are obtained with beam tests and the
Transient Current Technique
Characterisation of novel thin n-in-p planar pixel modules for the ATLAS Inner Tracker upgrade
In view of the high luminosity phase of the LHC (HL-LHC) to start operation
around 2026, a major upgrade of the tracker system for the ATLAS experiment is
in preparation. The expected neutron equivalent fluence of up to 2.4 * 1e16 1
MeV neq./cm2 at the innermost layer of the pixel detector poses the most severe
challenge. Thanks to their low material budget and high charge collection
efficiency after irradiation, modules made of thin planar pixel sensors are
promising candidates to instrument these layers. To optimise the sensor layout
for the decreased pixel cell size of 50 * 50 {\mu}m2, TCAD device simulations
are being performed to investigate the charge collection efficiency before and
after irradiation. In addition, sensors of 100-150 {\mu}m thickness,
interconnected to FE-I4 read-out chips featuring the previous generation pixel
cell size of 50 * 250 {\mu}m2, are characterised with testbeams at the CERN-SPS
and DESY facilities. The performance of sensors with various designs,
irradiated up to a fluence of 1 * 1e16 neq./cm2, is compared in terms of charge
collection and hit efficiency. A replacement of the two innermost pixel layers
is foreseen during the lifetime of HL-LHC. The replacement will require several
months of intervention, during which the remaining detector modules cannot be
cooled. They are kept at room temperature, thus inducing an annealing. The
performance of irradiated modules will be investigated with testbeam campaigns
and the method of accelerated annealing at higher temperatures.Comment: 11 pages, 10 figures, proceedings of the PSD Conference 201
The role of the rigged Hilbert space in Quantum Mechanics
There is compelling evidence that, when continuous spectrum is present, the
natural mathematical setting for Quantum Mechanics is the rigged Hilbert space
rather than just the Hilbert space. In particular, Dirac's bra-ket formalism is
fully implemented by the rigged Hilbert space rather than just by the Hilbert
space. In this paper, we provide a pedestrian introduction to the role the
rigged Hilbert space plays in Quantum Mechanics, by way of a simple, exactly
solvable example. The procedure will be constructive and based on a recent
publication. We also provide a thorough discussion on the physical significance
of the rigged Hilbert space.Comment: 29 pages, 2 figures; a pedestrian introduction to the rigged Hilbert
spac
Lazy-CSeq-SP: Boosting Sequentialization-Based Verification of Multi-threaded C Programs via Symbolic Pruning of Redundant Schedules
Abstract. Sequentialization has been shown to be an effective symbolic verification technique for concurrent C programs using POSIX threads. Lazy-CSeq, a tool that applies a lazy sequentialization scheme, has won the Concurrency division of the last two editions of the Competition on Software Verification. The tool encodes all thread schedules up to a given bound into a single non-deterministic sequential C program and then invokes a C model checker. This paper presents a novel optimized imple-mentation of lazy sequentialization, which integrates symbolic pruning of redundant schedules into the encoding. Experimental evaluation shows that our tool outperforms Lazy-CSeq significantly on many benchmarks
Size effect on properties of varistors made from zinc oxide nanoparticles through low temperature spark plasma sintering
Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8-nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at roomtemperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as-prepared ceramics are based on scanning electron microscopy and X-ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current–voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 8C
Spatial Awareness is Related to Moderate Intensity Running during a Collegiate Rugby Match
International Journal of Exercise Science 9(5): 599-606, 2016. The purpose of the present study was to evaluate the relationship between spatial awareness, agility, and distance covered in global positioning system (GPS) derived velocity zone classifications during a collegiate rugby match. Twelve American collegiate rugby union players (mean±SD; age: 21.2±1.4 y; weight: 85.0±16.0 kg; 7 forwards & 5 backs) on a single team volunteered to participate in this investigation. The distances travelled at low (walking/jogging; \u3c2.7m/s), moderate (cruising/striding; 2.7-5.0 m/s), and high intensities (running/sprinting; \u3e5.0 m/s) were measured for each player using GPS sensors and normalized according to playing time during an official USA Rugby match. Spatial awareness was measured as visual tracking speed from one core session of a 3-dimensional multiple-object-tracking speed (3DMOTS) test (1.35±0.59 cm·sec-1). Agility was assessed utilizing the pro agility (5.05±0.28 sec) and t drill (10.62±0.39 sec). Analysis of variance revealed that athletes travelled the greatest distance during walking/jogging (39.5±4.5 m·min-1) and least distance during running/sprinting (4.9±3.5 m·min-1). Pearson product moment correlations revealed that only distance covered while cruising/striding (20.9±6.5 m·min-1) was correlated to spatial awareness (r=0.798, p=0.002). Agility did not correlate to distance covered at any velocity zone or spatial awareness. Spatial awareness, as determined by 3DMOTS, appears to be related to the moderate intensity movement patterns of rugby union athletes
Secular changes in the quiescence of WZ Sge: the development of a cavity in the inner disk
We find a dimming during optical quiescence of the cataclysmic variable WZ
Sge by about half a magnitude between superoutbursts. We connect the dimming
with the development of a cavity in the inner part of the accretion disk. We
suggest that, when the cavity is big enough, accretion of material is governed
by the magnetic field of the white dwarf and pulsations from the weakly
magnetic white dwarf appear. The time scale of forming the cavity is about a
decade, and it persists throughout the whole quiescent phase. Such a cavity can
be accommodated well by the proposed magnetic propeller model for WZ Sge, where
during quiescence mass is being expelled by the magnetic white dwarf from the
inner regions of the accretion disk to larger radii.Comment: 10 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics; following referee report, many textual changes, figures
improved, more historic data added, conclusions unchange
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