3,230 research outputs found
Heavily Irradiated N-in-p Thin Planar Pixel Sensors with and without Active Edges
We present the results of the characterization of silicon pixel modules
employing n-in-p planar sensors with an active thickness of 150
m, produced at MPP/HLL, and 100-200 m thin active
edge sensor devices, produced at VTT in Finland. These thin sensors are
designed as candidates for the ATLAS pixel detector upgrade to be operated at
the HL-LHC, as they ensure radiation hardness at high fluences. They are
interconnected to the ATLAS FE-I3 and FE-I4 read-out chips. Moreover, the
n-in-p technology only requires a single side processing and thereby it is a
cost-effective alternative to the n-in-n pixel technology presently employed in
the LHC experiments. High precision beam test measurements of the hit
efficiency have been performed on these devices both at the CERN SpS and at
DESY, Hamburg. We studied the behavior of these sensors at different bias
voltages and different beam incident angles up to the maximum one expected for
the new Insertable B-Layer of ATLAS and for HL-LHC detectors. Results obtained
with 150 m thin sensors, assembled with the new ATLAS FE-I4 chip
and irradiated up to a fluence of
410, show that they are
excellent candidates for larger radii of the silicon pixel tracker in the
upgrade of the ATLAS detector at HL-LHC. In addition, the active edge
technology of the VTT devices maximizes the active area of the sensor and
reduces the material budget to suit the requirements for the innermost layers.
The edge pixel performance of VTT modules has been investigated at beam test
experiments and the analysis after irradiation up to a fluence of
510 has been performed
using radioactive sources in the laboratory.Comment: Proceedings for iWoRiD 2013 conference, submitted to JINS
Thin n-in-p pixel sensors and the SLID-ICV vertical integration technology for the ATLAS upgrade at the HL-LHC
The R&D activity presented is focused on the development of new modules for
the upgrade of the ATLAS pixel system at the High Luminosity LHC (HL-LHC). The
performance after irradiation of n-in-p pixel sensors of different active
thicknesses is studied, together with an investigation of a novel
interconnection technique offered by the Fraunhofer Institute EMFT in Munich,
the Solid-Liquid-InterDiffusion (SLID), which is an alternative to the standard
solder bump-bonding. The pixel modules are based on thin n-in-p sensors, with
an active thickness of 75 um or 150 um, produced at the MPI Semiconductor
Laboratory (MPI HLL) and on 100 um thick sensors with active edges, fabricated
at VTT, Finland. Hit efficiencies are derived from beam test data for thin
devices irradiated up to a fluence of 4e15 neq/cm^2. For the active edge
devices, the charge collection properties of the edge pixels before irradiation
is discussed in detail, with respect to the inner ones, using measurements with
radioactive sources. Beyond the active edge sensors, an additional ingredient
needed to design four side buttable modules is the possibility of moving the
wire bonding area from the chip surface facing the sensor to the backside,
avoiding the implementation of the cantilever extruding beyond the sensor area.
The feasibility of this process is under investigation with the FE-I3 SLID
modules, where Inter Chip Vias are etched, employing an EMFT technology, with a
cross section of 3 um x 10 um, at the positions of the original wire bonding
pads.Comment: Proceedings for Pixel 2012 Conference, submitted to NIM A, 6 page
Production and Characterisation of SLID Interconnected n-in-p Pixel Modules with 75 Micrometer Thin Silicon Sensors
The performance of pixel modules built from 75 micrometer thin silicon
sensors and ATLAS read-out chips employing the Solid Liquid InterDiffusion
(SLID) interconnection technology is presented. This technology, developed by
the Fraunhofer EMFT, is a possible alternative to the standard bump-bonding. It
allows for stacking of different interconnected chip and sensor layers without
destroying the already formed bonds. In combination with Inter-Chip-Vias (ICVs)
this paves the way for vertical integration. Both technologies are combined in
a pixel module concept which is the basis for the modules discussed in this
paper.
Mechanical and electrical parameters of pixel modules employing both SLID
interconnections and sensors of 75 micrometer thickness are covered. The
mechanical features discussed include the interconnection efficiency, alignment
precision and mechanical strength. The electrical properties comprise the
leakage currents, tuning characteristics, charge collection, cluster sizes and
hit efficiencies. Targeting at a usage at the high luminosity upgrade of the
LHC accelerator called HL-LHC, the results were obtained before and after
irradiation up to fluences of
(1 MeV neutrons).Comment: 16 pages, 22 figure
Characterization of Thin Pixel Sensor Modules Interconnected with SLID Technology Irradiated to a Fluence of 2\,n/cm
A new module concept for future ATLAS pixel detector upgrades is presented,
where thin n-in-p silicon sensors are connected to the front-end chip
exploiting the novel Solid Liquid Interdiffusion technique (SLID) and the
signals are read out via Inter Chip Vias (ICV) etched through the front-end.
This should serve as a proof of principle for future four-side buttable pixel
assemblies for the ATLAS upgrades, without the cantilever presently needed in
the chip for the wire bonding.
The SLID interconnection, developed by the Fraunhofer EMFT, is a possible
alternative to the standard bump-bonding. It is characterized by a very thin
eutectic Cu-Sn alloy and allows for stacking of different layers of chips on
top of the first one, without destroying the pre-existing bonds. This paves the
way for vertical integration technologies.
Results of the characterization of the first pixel modules interconnected
through SLID as well as of one sample irradiated to \,\neqcm{}
are discussed.
Additionally, the etching of ICV into the front-end wafers was started. ICVs
will be used to route the signals vertically through the front-end chip, to
newly created pads on the backside. In the EMFT approach the chip wafer is
thinned to (50--60)\,m.Comment: Proceedings to PSD
Application of a new interconnection technology for the ATLAS pixel upgrade at SLHC
We present an R&D activity aiming towards a new detector concept in the framework of the ATLAS pixel detector upgrade exploiting a vertical integration technology developed at the Fraunhofer Institute IZMMunich. The Solid-Liquid InterDiffusion (SLID) technique is investigated as an alternative to the bump-bonding process. We also investigate the extraction of the signals from the back of the read-out chip through Inter-Chip-Vias to achieve a higher fraction of active area with respect to the present ATLAS pixel module. We will present the layout and the first results obtained with a production of test-structures designed to investigate the SLID interconnection efficiency as a function of different parameters, i.e. the pixel size and pitch, as well as the planarity of the underlying layers
Mutations in the C-terminal region of the HIV-1 reverse transcriptase and their correlation with drug resistance associated mutations and antiviral treatment
<p>Abstract</p> <p>Objective</p> <p>Replication of HIV-1 after cell entry is essentially dependent on the reverse transcriptase (RT). Antiretroviral drugs impairing the function of the RT currently aim at the polymerase subunit. One reason for failure of antiretroviral treatment is the evolvement of resistance-associated mutations in the viral genome. For RT inhibitors, almost all identified mutations are located within the polymerase; therefore, general genotyping confines to investigate this subunit. Recently several studies have shown that substitutions within the RNase H and the connection domain increase antiviral drug-resistance in vitro, and some of them are present in patient isolates.</p> <p>Aim</p> <p>The aim of the present study was to investigate the prevalence of these substitutions and their association with mutations in the polymerase domain arising during antiretroviral treatment.</p> <p>Materials and methods</p> <p>We performed genotypic analyzes on seventy-four virus isolates derived from treated and untreated patients, followed at the HIV Centre of the Johann Wolfgang Goethe University Hospital (Frankfurt/Main, Germany). We subsequently analysed the different substitutions in the c-terminal region to evaluate whether there were associations with each other, n-terminal substitutions or with antiretroviral treatment.</p> <p>Results</p> <p>We identified several primer grip substitutions, but almost all of them were located in the connection domain. This is consistent with other in-vivo studies, in which especially the primer grip residues located in the RNase H were unvaried. Furthermore, we identified other substitutions in the connection domain and in the RNase H. Especially E399D seemed to be associated with an antiretroviral treatment and N-terminal resistance-delivering mutations.</p> <p>Conclusion</p> <p>Some of the identified substitutions were associated with antiviral treatment and drug resistance-associated mutations. Due to the low prevalence of C-terminal mutations and as only a few of them could be associated with antiviral treatment and N-terminal resistance-delivering mutations, we would not recommend routinely testing of the C-terminal RT region.</p
Spectroscopy of Po
Prompt, in-beam rays following the reaction Yb + 142 MeV
Si were measured at the ATLAS facility using 10 Compton-suppressed Ge
detectors and the Fragment Mass Analyzer. Transitions in Po were
identified and placed using -ray singles and coincidence data gated on
the mass of the evaporation residues. A level spectrum up to
J10 was established. The structure of Po is more
collective than that observed in the heavier polonium isotopes and indicates
that the structure has started to evolve towards the more collective nature
expected for deformed nuclei.Comment: 8 pages, revtex 3.0, 4 figs. available upon reques
Peripheral heavy ion collisions as a probe of the nuclear gluon distribution
At high energies a quark-gluon plasma is expected to be formed in heavy ion
collisions at RHIC and LHC. The theoretical description of these processes is
directly associated to a complete knowledge of the details of medium effects in
the nuclear gluon distribution. In this paper we analyze the possibility to
constraint the behavior of this distribution considering peripheral heavy ion
collisions. We reanalyze the photoproduction of heavy quarks for the deduction
of the in-medium gluon distribution using three current parameterizations for
this parton distribution. Moreover, we show that the elastic photoproduction of
vector mesons is a potential process to probe the nuclear gluon distribution.Comment: 8 figures, accepted for publication in Physicsl review
Vector Meson Photoproduction from the BFKL Equation II: Phenomenology
Diffractive vector meson photoproduction accompanied by proton dissociation
is studied for large momentum transfer. The process is described by the
non-forward BFKL equation which we use to compare to data collected at the HERA
collider.Comment: 39 pages, 29 figure
Virtual photon structure functions and positivity constraints
We study the three positivity constraints among the eight virtual photon
structure functions, derived from the Cauchy-Schwarz inequality and which are
hence model-independent. The photon structure functions obtained from the
simple parton model show quite different behaviors in a massive quark or a
massless quark case, but they satisfy, in both cases, the three positivity
constraints. We then discuss an inequality which holds among the unpolarized
and polarized photon structure functions , and
, in the kinematic region , where is the mass squared of the probe (target) photon, and we examine
whether this inequality is satisfied by the perturbative QCD results.Comment: 24 pages, 13 eps figure
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