Search results for "beam"
showing 10 items of 2126 documents
Digitizing data acquisition and time-of-flight pulse processing for ToF-ERDA
2016
A versatile system to capture and analyze signals from multi channel plate (MCP) based time-of-flight detectors and ionization based energy detectors such as silicon diodes and gas ionization chambers (GIC) is introduced. The system is based on commercial digitizers and custom software. It forms a part of a ToF-ERDA spectrometer, which has to be able to detect recoil atoms of many different species and energies. Compared to the currently used analogue electronics the digitizing system provides comparable time-of-flight resolution and improved hydrogen detection efficiency, while allowing the operation of the spectrometer be studied and optimized after the measurement. The hardware, data acq…
Trajectory bending and energy spreading of charged ions in time-of-flight telescopes used for ion beam analysis
2014
Carbon foil time pick-up detectors are widely used in pairs in ion beam applications as time-of-flight detectors. These detectors are suitable for a wide energy range and for all ions but at the lowest energies the tandem effect limits the achievable time of flight and therefore the energy resolution. Tandem effect occurs when an ion passes the first carbon foil of the timing detector and its charge state is changed. As the carbon foil of the first timing detector has often a non-zero voltage the ion can accelerate or decelerate before and after the timing detector. The combination of different charge state properties before and after the carbon foil now induces spread to the measured times…
Time-of-flight - Energy spectrometer for elemental depth profiling - Jyväskylä design
2014
Abstract A new time-of-flight elastic recoil detection spectrometer has been built, and initially the main effort was focused in getting good timing resolution and high detection efficiency for light elements. With the ready system, a 154 ps timing resolution was recorded for scattered 4.8 MeV 4 He 2+ ions. The hydrogen detection efficiency was from 80% to 20% for energies from 100 keV to 1 MeV, respectively, and this was achieved by having an additional atomic layer deposited Al 2 O 3 coating on the first timing detector’s carbon foil. The data acquisition system utilizes an FPGA-card to time-stamp every time-of-flight and energy event with 25 ns resolution. The different origins of the ba…
Comparison of laser and power bleaching techniques in tooth color change
2017
BACKGROUND Laser-assisted bleaching uses laser beam to accelerate release of free radicals within the bleaching gel to decrease time of whitening procedure. The aim of this study was to compare the efficacy of power bleaching using Opalescence Xtra Boost® and laser bleaching technique using LaserSmile gel and diode laser as an activator in their tooth whitening capacity. MATERIAL AND METHODS Student t test showed that the laser bleaching group significantly outperformed the power bleaching group in changing ∆E (p=0.977). RESULTS Similarly, while comparing the groups in changing ∆L, the laser bleaching group indicated significantly superior results (p=0.953). Statistical data from student t …
Cross-section-constrained top-quark mass measurement from dilepton events at the tevatron
2008
We report the first top quark mass measurement that uses a cross section constraint to improve the mass determination. This measurement is made with a dilepton $t\bar{t}$ event sample collected with the CDF II detector. From a data sample corresponding to an integrated luminosity of 1.2 fb$^{-1}$, we measure a top quark mass of $\rm{170.7^{+4.2}_{-3.9}(stat)\pm2.6(syst)}$ $\rm{\pm2.4(theory) GeV/{\it{c}}^{2}}$. The measurement without the cross section constraint results in a top quark mass of $\rm{169.7^{+5.2}_{-4.9}(stat)\pm3.1(syst) GeV/{\it{c}}^{2}}$.
Combination of D0 measurements of the top quark mass
2017
We present a combination of measurements of the top quark mass by the D0 experiment in the lepton+jets and dilepton channels. We use all the data collected in Run I (1992--1996) at $\sqrt s=1.8$ TeV and Run II (2001--2011) at $\sqrt s=1.96$ TeV of the Tevatron $p \bar{p}$ collider, corresponding to integrated luminosities of 0.1 fb$^{-1}$ and 9.7 fb$^{-1}$, respectively. The combined result is: $m_t = 174.95 \pm0.40\,{\rm(stat)} \pm 0.64\,{\rm(syst)}\,{\rm{GeV}}=174.95 \pm 0.75 \, {\rm{GeV}}$.
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
2018
The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of √s=1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is At¯tFB=0.128±0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions.
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
2016
We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV.
Fractional viscoelastic beam under torsion
2017
Abstract This paper introduces a study on twisted viscoelastic beams, having considered fractional calculus to capture the viscoelastic behaviour. Further another novelty of this paper is extending a recent numerical approach, labelled line elementless method (LEM), to viscoelastic beams. The latter does not require any discretization neither in the domain nor in the boundary. Some numerical applications have been reported to demonstrate the efficiency and accuracy of the method.
Bloch Modes Coupling in Photonic Crystal Waveguides
2005
We investigate the properties of Bloch modes inside a photonic crystal waveguide. By using simultaneously a near field optical microscope and a transmittance setup, we demonstrate that Bloch modes having different parity are coupled.