101 research outputs found
New VR magnification ratios of QSO 0957+561
We present VR magnification ratios of QSO 0957+561, which are inferred from
the GLITP light curves of Q0957+561A and new frames taken with the 2.56m Nordic
Optical Telescope about 14 months after the GLITP monitoring. From two
photometric approaches and a reasonable range for the time delay in the system
(415-430 days), we do not obtain achromatic optical continuum ratios, but
ratios depending on the wavelength. These new measurements are consistent with
differential extinction in the lens galaxy, the Lyman limit system, the damped
Ly-alpha system, or the host galaxy of the QSO. The possible values for the
differential extinction and the ratio of total to selective extinction in the V
band are reasonable. Moreover, crude probability arguments suggest that the ray
paths of the two components cross a similar dusty environment, including a
network of compact dust clouds and compact dust voids. As an alternative (in
fact, the usual interpretation of the old ratios), we also try to explain the
new ratios as caused by gravitational microlensing in the deflector. From
magnification maps for each of the gravitationally lensed images, using
different fractions of the surface mass density represented by the microlenses,
as well as different sizes and profiles of the V-band and R-band sources,
several synthetic distributions of V-band and R-band ratios are derived. In
some gravitational scenarios, there is an apparent disagreement between the
observed pair of ratios and the simulated distributions. However, several
microlensing pictures work well. To decide between either extinction, or
microlensing, or a mixed scenario (extinction + microlensing), new
observational and interpretation efforts are required.Comment: PS and PDF versions are created from the LaTeX file and 5 EPS
figures, two additional figues (Figs. 6 and 7) in JPEG format, scheduled for
the ApJ 20 January 2005 issu
Mapping The In-Plane Electric Field Inside Irradiated Diodes
A significant aspect of the Phase-II Upgrade of the ATLAS detector is the replacement of the current Inner Detector with the ATLAS Inner Tracker (ITk). The ATLAS ITk is an all-silicon detector consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker have been developed to withstand the high radiation environment in the ATLAS detector after the High Luminosity Upgrade of the Large Hadron Collider at CERN, which will significantly increase the rate of particle collisions and resulting particle tracks. During their operation in the ATLAS detector, sensors for the ITk strip tracker are expected to accumulate fluences up to 1.61015neq/cm2 (including a safety factor of 1.5), which will significantly affect their performance. One characteristic of interest for highly irradiated sensors is the shape and homogeneity of the electric field inside its active area. For the results presented here, diodes with edge structures similar to full size ATLAS sensors were irradiated up to fluences comparable to those in the ATLAS ITk strip tracker and their electric fields mapped using a micro-focused X-ray beam (beam diameter 23m2). This study shows the extension and shape of the electric field inside highly irradiated diodes over a range of applied bias voltages. Additionally, measurements of the outline of the depleted sensor areas allow a comparison of the measured leakage current for different fluences with expectations for the corresponding active areas
Characterisation of strip silicon detectors for the ATLAS Phase-II Upgrade with a micro-focused X-ray beam
The planned HL-LHC (High Luminosity LHC) in 2025 is being designed to maximise
the physics potential through a sizable increase in the luminosity up to 6 · 1034 cm−2
s
−1
. A
consequence of this increased luminosity is the expected radiation damage at 3000 fb−1
after ten
years of operation, requiring the tracking detectors to withstand fluences to over 1 · 1016 1 MeV
neq/cm2
. In order to cope with the consequent increased readout rates, a complete re-design of the
current ATLAS Inner Detector (ID) is being developed as the Inner Tracker (ITk). Two proposed detectors for the ATLAS strip tracker region of the ITk were characterized at
the Diamond Light Source with a 3 µm FWHM 15 keV micro focused X-ray beam. The devices
under test were a 320 µm thick silicon stereo (Barrel) ATLAS12 strip mini sensor wire bonded
to a 130 nm CMOS binary readout chip (ABC130) and a 320 µm thick full size radial (end-cap)
strip sensor - utilizing bi-metal readout layers - wire bonded to 250 nm CMOS binary readout chips
(ABCN-25).
A resolution better than the inter strip pitch of the 74.5 µm strips was achieved for both detectors.
The effect of the p-stop diffusion layers between strips was investigated in detail for the wire bond
pad regions.
Inter strip charge collection measurements indicate that the effective width of the strip on the
silicon sensors is determined by p-stop regions between the strips rather than the strip pitch
Setups for eliminating static charge of the ATLAS18 strip sensors
Construction of the new all-silicon Inner Tracker (ITk), developed by the
ATLAS collaboration for the High Luminosity LHC, started in 2020 and is
expected to continue till 2028. The ITk detector will include 18,000 highly
segmented and radiation hard n+-in-p silicon strip sensors (ATLAS18), which are
being manufactured by Hamamatsu Photonics. Mechanical and electrical
characteristics of produced sensors are measured upon their delivery at several
institutes participating in a complex Quality Control (QC) program. The QC
tests performed on each individual sensor check the overall integrity and
quality of the sensor. During the QC testing of production ATLAS18 strip
sensors, an increased number of sensors that failed the electrical tests was
observed. In particular, IV measurements indicated an early breakdown, while
large areas containing several tens or hundreds of neighbouring strips with low
interstrip isolation were identified by the Full strip tests, and leakage
current instabilities were measured in a long-term leakage current stability
setup. Moreover, a high surface electrostatic charge reaching a level of
several hundreds of volts per inch was measured on a large number of sensors
and on the plastic sheets, which mechanically protect these sensors in their
paper envelopes. Accumulated data indicates a clear correlation between
observed electrical failures and the sensor charge-up. To mitigate the
above-described issues, the QC testing sites significantly modified the sensor
handling procedures and introduced sensor recovery techniques based on
irradiation of the sensor surface with UV light or application of intensive
flows of ionized gas. In this presentation, we will describe the setups
implemented by the QC testing sites to treat silicon strip sensors affected by
static charge and evaluate the effectiveness of these setups in terms of
improvement of the sensor performance
The significance of peroxisomes in secondary metabolite biosynthesis in filamentous fungi
Peroxisomes are ubiquitous organelles characterized by a protein-rich matrix surrounded by a single membrane. In filamentous fungi, peroxisomes are crucial for the primary metabolism of several unusual carbon sources used for growth (e.g. fatty acids), but increasing evidence is presented that emphasize the crucial role of these organelles in the formation of a variety of secondary metabolites. In filamentous fungi, peroxisomes also play a role in development and differentiation whereas specialized peroxisomes, the Woronin bodies, play a structural role in plugging septal pores. The biogenesis of peroxisomes in filamentous fungi involves the function of conserved PEX genes, as well as genes that are unique for these organisms. Peroxisomes are also subject to autophagic degradation, a process that involves ATG genes. The interplay between organelle biogenesis and degradation may serve a quality control function, thereby allowing a continuous rejuvenation of the organelle population in the cells
Identification and recovery of ATLAS18 strip sensors with high surface static charge
The new all-silicon Inner Tracker (ITk) is being constructed by the ATLAS collaboration to track charged particles produced at the High-Luminosity LHC. The outer portion of the ITk detector will include nearly 18,000 highly segmented and radiation hard silicon strip sensors (ATLAS18 design). Throughout the production of 22,000 sensors, the strip sensors are subjected to a comprehensive suite of mechanical and electrical tests as part of the Quality Control (QC) program. In a large fraction of the batches delivered to date, high surface electrostatic charge has been measured on both the sensors and the plastic sheets between which the sensors are packaged for shipping and handling rigidity. Aggregate data from across QC sites indicate a correlation between observed electrical failures and the sensor/plastic sheet charge build up. To mitigate these issues, the QC testing sites introduced recovery techniques involving UV light or flows of ionizing gas. Significant modifications to sensor handling procedures were made to prevent subsequent build up of static charge. This publication details a precise description of the issue, a variety of sensor recovery techniques, and trend analyses of sensors initially failing electrical tests (IV, strip scan, etc.)
Charge collection and field profile studies of heavily irradiated strip sensors for the ATLAS inner tracker upgrade
The ATLAS group has evaluated the charge collection in silicon microstrip sensors irradiated up to a fluence of 1×1016 neq/cm2, exceeding the maximum of 1.6×1015 neq/cm2 expected for the strip tracker during the high luminosity LHC (HL-LHC) period including a safety factor of 2. The ATLAS12, n+-on-p type sensor, which is fabricated by Hamamatsu Photonics (HPK) on float zone (FZ) substrates, is the latest barrel sensor prototype. The charge collection from the irradiated 1×1 cm2 barrel test sensors has been evaluated systematically using penetrating β-rays and an Alibava readout system. The data obtained at different measurement sites are compared with each other and with the results obtained from the previous ATLAS07 design. The results are very consistent, in particular, when the deposit charge is normalized by the sensor's active thickness derived from the edge transient current technique (edge-TCT) measurements. The measurements obtained using β-rays are verified to be consistent with the measurements using an electron beam. The edge-TCT is also effective for evaluating the field profiles across the depth. The differences between the irradiated ATLAS07 and ATLAS12 samples have been examined along with the differences among the samples irradiated with different radiation sources: neutrons, protons, and pions. The studies of the bulk properties of the devices show that the devices can yield a sufficiently large signal for the expected fluence range in the HL-LHC, thereby acting as precision tracking sensors
Embedded pitch adapters: a high-yield interconnection solution for strip sensors
A proposal to fabricate large area strip sensors with integrated, or embedded, pitch adapters is presented for the End-cap part of the Inner Tracker in the ATLAS experiment. To implement the embedded pitch adapters, a second metal layer is used in the sensor fabrication, for signal routing to the ASICs. Sensors with different embedded pitch adapters have been fabricated in order to optimize the design and technology. Inter-strip capacitance, noise, pick-up, cross-talk, signal efficiency, and fabrication yield have been taken into account in their design and fabrication. Inter-strip capacitance tests taking into account all channel neighbors reveal the important differences between the various designs considered. These tests have been correlated with noise figures obtained in full assembled modules, showing that the tests performed on the bare sensors are a valid tool to estimate the final noise in the full module. The full modules have been subjected to test beam experiments in order to evaluate the incidence of cross-talk, pick-up, and signal loss. The detailed analysis shows no indication of cross-talk or pick-up as no additional hits can be observed in any channel not being hit by the beam above 170 mV threshold, and the signal in those channels is always below 1% of the signal recorded in the channel being hit, above 100 mV threshold. First results on irradiated mini-sensors with embedded pitch adapters do not show any change in the interstrip capacitance measurements with only the first neighbors connected
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