263 research outputs found
Investigation of surface structure, electrokinetic and stability properties of highly dispersed HoâOâ-YbâOâ/SiOâ nanocomposites
A series of highly dispersed Ho2O3âYb2O3/SiO2 nanocomposites was synthesized using a liquid-phase method and examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorptionâdesorption, transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), and photon correlation spectroscopy (PCS). X-ray fluorescence spectrometry (XRF) confirmed a similar amount of weight percentage of Ho, Yb and Si oxides in the prepared samples. Samples HoYbSi1 (Ho2O3:Yb2O3:SiO2â=â0.5:10:89.5, wt. %), HoYbSi2 (Ho2O3:Yb2O3:SiO2â=â1:10:89, wt. %) and HoYbSi3 (Ho2O3:Yb2O3:SiO2â=â2:10:88, wt. %) calcined at 550 °C are amorphous. TEM and SEM analysis confirm a sphere-like morphology with a quite homogeneous size and shape. As compared with the initial silica, the agglomerated particles of nanocomposites in the aqueous medium are in the range from 200 to 850 nm according to PCS data. The effect of anionic polyacrylic acid (PAA) adsorption on fumed silica (SiO2) and Ho2O3âYb2O3/SiO2 nanocomposite surfaces on suspension stability was studied. The turbidymetry method was used to monitor the initial silica and triple nanooxides suspensions stability as a function of time
DECam integration tests on telescope simulator
The Dark Energy Survey (DES) is a next generation optical survey aimed at
measuring the expansion history of the universe using four probes: weak
gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and
Type Ia supernovae. To perform the survey, the DES Collaboration is building
the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera
which will be mounted at the Blanco 4-meter telescope at the Cerro Tololo
Inter- American Observatory. DES will survey 5000 square degrees of the
southern galactic cap in 5 filters (g, r, i, z, Y). DECam will be comprised of
74 250 micron thick fully depleted CCDs: 62 2k x 4k CCDs for imaging and 12 2k
x 2k CCDs for guiding and focus. Construction of DECam is nearing completion.
In order to verify that the camera meets technical specifications for DES and
to reduce the time required to commission the instrument, we have constructed a
full sized telescope simulator and performed full system testing and
integration prior to shipping. To complete this comprehensive test phase we
have simulated a DES observing run in which we have collected 4 nights worth of
data. We report on the results of these unique tests performed for the DECam
and its impact on the experiments progress.Comment: Proceedings of the 2nd International Conference on Technology and
Instrumentation in Particle Physics (TIPP 2011). To appear in Physics
Procedia. 8 pages, 3 figure
Commissioning and initial performance of the Dark Energy Camera liquid nitrogen cooling system
The Dark Energy Camera and its cooling system has been shipped to Cerro Tololo Inter-American Observatory in Chile for installation onto the Blanco 4m telescope. Along with the camera, the cooling system has been installed in the CoudĂŠ room at the Blanco Telescope. Final installation of the cooling system and operations on the telescope is planned for the middle of 2012. Initial commissioning experiences and cooling system performance is described
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
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Characterization of DECam focal plane detectors
DECam is a 520 Mpix, 3 square-deg FOV imager being built for the Blanco 4m Telescope at CTIO. This facility instrument will be used for the 'Dark Energy Survey' of the southern galactic cap. DECam has chosen 250 ?m thick CCDs, developed at LBNL, with good QE in the near IR for the focal plane. In this work we present the characterization of these detectors done by the DES team, and compare it to the DECam technical requirements. The results demonstrate that the detectors satisfy the needs for instrument
Performance and Operation of the CMS Electromagnetic Calorimeter
The operation and general performance of the CMS electromagnetic calorimeter
using cosmic-ray muons are described. These muons were recorded after the
closure of the CMS detector in late 2008. The calorimeter is made of lead
tungstate crystals and the overall status of the 75848 channels corresponding
to the barrel and endcap detectors is reported. The stability of crucial
operational parameters, such as high voltage, temperature and electronic noise,
is summarised and the performance of the light monitoring system is presented
Conceptual Design of the Modular Detector and Readout System for the CMB-S4 survey experiment
We present the conceptual design of the modular detector and readout system
for the Cosmic Microwave Background Stage 4 (CMB-S4) ground-based survey
experiment. CMB-S4 will map the cosmic microwave background (CMB) and the
millimeter-wave sky to unprecedented sensitivity, using 500,000 superconducting
detectors observing from Chile and Antarctica to map over 60 percent of the
sky. The fundamental building block of the detector and readout system is a
detector module package operated at 100 mK, which is connected to a readout and
amplification chain that carries signals out to room temperature. It uses
arrays of feedhorn-coupled orthomode transducers (OMT) that collect optical
power from the sky onto dc-voltage-biased transition-edge sensor (TES)
bolometers. The resulting current signal in the TESs is then amplified by a
two-stage cryogenic Superconducting Quantum Interference Device (SQUID) system
with a time-division multiplexer to reduce wire count, and matching
room-temperature electronics to condition and transmit signals to the data
acquisition system. Sensitivity and systematics requirements are being
developed for the detector and readout system over a wide range of observing
bands (20 to 300 GHz) and optical powers to accomplish CMB-S4's science goals.
While the design incorporates the successes of previous generations of CMB
instruments, CMB-S4 requires an order of magnitude more detectors than any
prior experiment. This requires fabrication of complex superconducting circuits
on over 10 square meters of silicon, as well as significant amounts of
precision wiring, assembly and cryogenic testing.Comment: 25 pages, 15 figures, presented at and published in the proceedings
of SPIE Astronomical Telescopes and Instrumentation 202
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