Search results for "Acceleration"
showing 10 items of 345 documents
Computational Approach to Gravitational Waves Forms in Stellar Systems as Complex Structures through Keplerian Parameters
2009
In this paper we investigate the gravitational waves emission by stellar dynamical structures as complex systems in the quadrupole approximation considering bounded and unbounded orbits. Precisely, after deriving analytical expressions for the gravitational wave luminosity, the total energy output and gravitational radiation amplitude, we present a computational approach to evaluate the gravitational wave-forms from elliptical, circular, parabolic and hyperbolic orbits as a function of Keplerian parameters.
A novel cooling scheme for antiprotons
2006
We propose a novel technique which uses laser-cooled negative osmium ions for sympathetic cooling of antiprotons. Temperatures down to the sub-millikelvin range might be achievable. These antiprotons could be used to form antihydrogen at ultra-cold temperatures, thus allowing efficient magnetic trapping of antihydrogen for high-resolution laser spectroscopy. Antihydrogen at sub-millikelvin temperatures might also enable first direct measurements of the gravitational acceleration of antimatter. Currently, no other technique exists which allows the cooling of large numbers of antiprotons to temperatures below that of the surrounding trap.
Thermal and non-thermal signatures of the Unruh effect in Casimir-Polder forces
2014
We show that Casimir-Polder forces between two relativistic uniformly accelerated atoms exhibit a transition from the short distance thermal-like behavior predicted by the Unruh effect, to a long distance non-thermal behavior, associated with the breakdown of a local inertial description of the system. This phenomenology extends the Unruh thermal response detected by a single accelerated observer to an accelerated spatially extended system of two particles, and we identify the characteristic length scale for this crossover with the inverse of the proper acceleration of the two atoms. Our results are derived separating at fourth order in perturbation theory the contributions of vacuum fluctu…
τ hadronic spectral function moments in a nonpower QCD perturbation theory
2016
Abstract The moments of the hadronic spectral functions are of interest for the extraction of the strong coupling and other QCD parameters from the hadronic decays of the τ lepton. We consider the perturbative behavior of these moments in the framework of a QCD nonpower perturbation theory, defined by the technique of series acceleration by conformal mappings, which simultaneously implements renormalization-group summation and has a tame large-order behavior. Two recently proposed models of the Adler function are employed to generate the higher order coefficients of the perturbation series and to predict the exact values of the moments, required for testing the properties of the perturbativ…
Parity violation correlations in light muonic atoms
1989
The 2 S -1 S transition in light muonic atoms is very sensitive to parity violation correlations induced via neutral currents. Observables depending on these transitions such as the photon polarization and the angular correlation between the emitted radiation and the atom polarization are a clear signal of weak neutral currents in atoms. We find the relation between the lepton and quark couplings and these observables emphasizing the effect of the nuclear spin. The results expected in muonic, atoms μ- 4 He and μ- 3 He are given.
Spatial distribution of air kerma rate and impact of accelerating voltage on the quality of an ultra soft X-ray beam generated by a cold cathode tube…
2015
Abstract Ultrasoft X-ray characteristic aluminum K alpha line (Al Kα with energy of 1.5 keV) is used in radiobiological experiments to study the effect of radiation on biological matter. A simple method to generate a continuous beam of those X-ray radiations is to bombarding an aluminum target with accelerated electrons using high voltage (HV). In this work, by varying the HV we study the characteristics of a photon beam generated by means of a cold cathode transmission X-ray tube. The anode is a thin (16 μm) aluminum foil supported by a copper grid. The spatial distribution of air kerma is measured using gafchromic films of HD-810 calibrated with a parallel plate free-air ionization chambe…
Fourier-Accelerated Polymer Dynamics
1994
Fourier acceleration methods are applied to simulations of two-dimensional isolated ring polymers of up to N = 64 monomers. Three simulation schemes are compared: (i) a simple Langevin simulation with local updating, (ii) a Langevin algorithm with Fourier acceleration, and (iii) a Fourier accelerated Langevin algorithm combined with Metropolis acceptance of the moves (Force Biased Monte Carlo). In contrast to (i) and (ii), method (iii) is not hampered by systematic discretization errors, which, in case (ii), seem to grow systematically with chain length N. The results on the correlation time 4 are not very accurate, however, the data are in rough agreement with τ s N z with z= 2.5 (Rouse mo…
Amorphous silica modeled with truncated and screened Coulomb interactions: A molecular dynamics simulation study
2007
We show that finite-range alternatives to the standard long-range BKS pair potential for silica might be used in molecular dynamics simulations. We study two such models that can be efficiently simulated since no Ewald summation is required. We first consider the Wolf method, where the Coulomb interactions are truncated at a cutoff distance r_c such that the requirement of charge neutrality holds. Various static and dynamic quantities are computed and compared to results from simulations using Ewald summations. We find very good agreement for r_c ~ 10 Angstroms. For lower values of r_c, the long--range structure is affected which is accompanied by a slight acceleration of dynamic properties…
Reference beam dynamics layout for the SC CW heavy ion HELIAC at GSI
2020
Abstract The standalone superconducting continuous wave heavy ion linac HELIAC (HElmholtz LInear ACcelerator) is a common project of GSI Helmholtz Centre for Heavy Ion Research and Helmholtz Institute Mainz (HIM) under key support of Goethe University Frankfurt (IAP) and in collaboration with National Research Nuclear University MEPhI and NRC “Kurchatov Institute” ITEP. In 2017 the first superconducting section of the linac has been successfully commissioned and extensively tested with beam at GSI. The measurements sufficiently present the capability of 216.816 MHz multi-gap Crossbar H-mode (CH) DTL-structures. An acceleration of heavy ions up to the design beam energy and beyond has been r…
European vestibular experiments on the Spacelab-1 mission: 4. Thresholds of perception of whole-body linear oscillation.
1986
Thresholds for the detection of linear oscillatory motion at 0.3 Hz in the X, Y and Z body axes were determined during the flight of Spacelab-1 and on the ground pre- and post-flight, using the method of limits with a single staircase procedure. Pre-flight, Z axis thresholds (mean 0.077 ms-2) were significantly higher than X and Y thresholds (mean 0.029 ms-2). Measures obtained on three crew members in-flight exhibited thresholds greater, by a factor of 1.5-4.3, than those obtained pre-flight. Post-flight, two crew members had significantly elevated X and Y axis thresholds whereas the other two crew members had lowered thresholds in X, Y and Z axes. In general, thresholds had returned to pr…