Abstract
A major bottleneck in nanoparticle sizing is the lack of data comparability between techniques and between laboratories. However, this can be overcome by making the measurements traceable to ...the SI together with realistic uncertainty evaluation. In the present work, a novel approach is proposed to perform measurement uncertainty evaluation in a Bayesian framework by statistically modeling appropriately selected measurement data when no comprehensive physical model is available. The method is applied to the dimensional measurement of nanoparticles by atomic force microscopy (AFM) measurement and the calibration is performed by a multiple points calibration curve. Nevertheless, the proposed method can be applied to other microscopy techniques. The experimental data used to construct the statistical model are collected so that the influence of relevant measurement parameters can be assessed. An optimized experiment is designed under the intermediate precision conditions in order to limit the number of measurements to perform. Among the different influencing parameters, it is found that the AFM operator and image analyst do not significantly affect the measurement variability while the tip tapping force, the probe nature and the tip scan speed do. The particular case of gold nanoparticle of nominal diameter 30 nm is treated as an example of the method.
Size is the key feature of nanoparticle properties. Nanoparticle size distribution can be measured by microscopy technique and light scattering posterior to a separation technique. Discrepancies can ...be observed, especially in the case of polydisperse samples. Microscopy is more precise for size and shape measurement, while light scattering provides better information about concentration. An experiment is set up to investigate the feasibility of bringing comparability of Asymmetrical Flow Field-Flow Fractionation followed by Multi-Angle Light Scattering and AFM measurements. A sample made from a mixture of stock samples is built, after detailed characterisation of the stock samples. By obtaining comparability of MALS and AFM measurements, a new way to calibrate MALS instrument without the need for reference material is opened: using aliquots of the sample itself as a reference.
The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a ...significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.
Impact of low-dose electron irradiation on n+p silicon strip sensors Adam, W.; Baulieu, G.; Boudoul, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2015, Letnik:
803, Številka:
C
Journal Article
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The response of n+p silicon strip sensors to electrons from a 90Sr source was measured using a multi-channel read-out system with 25ns sampling time. The measurements were performed over a period of ...several weeks, during which the operating conditions were varied. The sensors were fabricated by Hamamatsu Photonics on 200μm thick float-zone and magnetic-Czochralski silicon. Their pitch was 80μm, and both p-stop and p-spray isolation of the n+ strips were studied. The electrons from the 90Sr source were collimated to a spot with a full-width-at-half-maximum of 2mm at the sensor surface, and the dose rate in the SiO2 at the maximum was about 50Gy(SiO2)/d. After only a few hours of making measurements, significant changes in charge collection and charge sharing were observed. Annealing studies, with temperatures up to 80°C and annealing times of 18h showed that the changes can only be partially annealed. The observations can be qualitatively explained by the increase of the positive oxide-charge density due to the ionization of the SiO2 by the radiation from the β source. TCAD simulations of the electric field in the sensor for different oxide-charge densities and different boundary conditions at the sensor surface support this explanation. The relevance of the measurements for the design of n+p strip sensors is discussed.
A search for supersymmetry or other new physics resulting in similar final states is presented using a data sample of 4.73 inverse femtobarns of pp collisions collected at sqrt(s)=7 TeV with the CMS ...detector at the LHC. Fully hadronic final states are selected based on the variable MT2, an extension of the transverse mass in events with two invisible particles. Two complementary studies are performed. The first targets the region of parameter space with medium to high squark and gluino masses, in which the signal can be separated from the standard model backgrounds by a tight requirement on MT2. The second is optimized to be sensitive to events with a light gluino and heavy squarks. In this case, the MT2 requirement is relaxed, but a higher jet multiplicity and at least one b-tagged jet are required. No significant excess of events over the standard model expectations is observed. Exclusion limits are derived for the parameter space of the constrained minimal supersymmetric extension of the standard model, as well as on a variety of simplified model spectra.
The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 $\mu$m thick n-type silicon sensors are irradiated with protons of different ...energies to fluences of up to $3 \cdot 10^{15}$ neq/cm$^2$. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations.
A search for pair-production of first generation scalar leptoquarks is performed in the final state containing an electron, a neutrino, and at least two jets using proton-proton collision data at ...inline image. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb super(-1. The number of observed events is in good agreement with the predictions for standard model processes. Prior CMS results in the dielectron channel are combined with this electron + neutrino search. A 95% confidence level combined lower limit is set on the mass of a first generation scalar leptoquark at 339 GeV for beta=0.5, where beta is the branching fraction of the leptoquark to an electron and a quark. These results represent the most stringent direct limits to date for values of beta greater than 0.05.)
A measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum, H sub(T), in the range 0.2<H sub(T)<2.5 TeV is presented. The data have ...been collected at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb super(-1). Comparisons are made between the data and the predictions of different QCD-based Monte Carlo models for multijet production. All models considered in this study are consistent with the data for H sub(T)>0.5 TeV. This measurement extends to an H sub(T) range that has not been explored before.
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