Search results for "Lung"
showing 10 items of 2389 documents
Strong effect of the electron spin on bremsstrahlung observed in the relativistic regime
2015
We have studied bremsstrahlung produced by polarized 2.1 MeV electrons colliding with a thin gold target. We have observed a strong correlation between the orientation of the electron spin and the angle of x-ray linear polarization at the x-ray high energy tip region. This indicates a dominance of the spin-orbit interaction in bremsstrahlung.
Theg-factor of highly charged ions
2015
Highly charged ions provide a unique opportunity to test our understanding of atomic properties under extreme conditions: The electric field strength seen by an electron bound to a nucleus at the distance of the Bohr radius ranges from 1010 V/cm in hydrogen to1016 V/cm in hydrogenlike uranium. The theory of quantum electrodynamics (QED) allows for calculation e.g. of binding energies, transition probabilities or magnetic moments. While at low fields QED is tested to very high precision, new, hypothetical nonlinear effects like photon- photon interaction or a violation of Lorentz symmetry may occur in strong fields which then would lead to an extension of the Standard Model. The ultra-high p…
Vector polarimetry at MaMi – Measurements of tensor correlation coefficients in e−bremsstrahlungs processes
2011
Electron/photon tensor-correlation coefficients may allow to design a polarimeter that can measure all components of beam polarization simultaneously—a so-called vector polarimeter. Besides its purpose as a beam diagnostic device this vector polarimeter would also allow to test theoretical predictions for the electron-photon polarization correlations at energies between 1 MeV and 3.5 MeV. As a first step we have set up a measurement of the helicity transfer to the photon as a function of energy which is based on the Compton absorption method.
Cu charge radii reveal a weak sub-shell effect at N=40
2016
Collinear laser spectroscopy on Cu58-75 isotopes was performed at the CERN-ISOLDE radioactive ion beam facility. In this paper we report on the isotope shifts obtained from these measurements. State-of-the-art atomic physics calculations have been undertaken in order to determine the changes in mean-square charge radii δ(r2)A,A′ from the observed isotope shifts. A local minimum is observed in these radii differences at N=40, providing evidence for a weak N=40 sub-shell effect. However, comparison of δ(r2)A,A′ with a droplet model prediction including static deformation deduced from the spectroscopic quadrupole moments, points to the persistence of correlations at N=40.
Does the plasma composition affect the long term evolution of relativistic jets?
2001
We study the influence of the matter content of extragalactic jets on their morphology, dynamics and emission properties. For this purpose we consider jets of extremely different compositions including pure leptonic and baryonic plasmas. Our work is based on two-dimensional relativistic hydrodynamic simulations of the long-term evolution of powerful extragalactic jets propagating into a homogeneous environment. The equation of state used in the simulations accounts for an arbitrary mixture of electrons, protons and electron-positron pairs. Using the hydrodynamic models we have also computed synthetic radio maps and the thermal Bremsstrahlung X-ray emission from their cavities. Although ther…
Nucleation kinetics in deionized charged colloidal model systems: A quantitative study by means of classical nucleation theory
2007
We have studied the nucleation kinetics of charged colloidal model systems under salt free conditions crystallizing in bcc structure covering a wide range of particle number densities $18\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}{\mathrm{m}}^{\ensuremath{-}3}\ensuremath{\le}n\ensuremath{\le}66.3\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}{\mathrm{m}}^{\ensuremath{-}3}$. We employed direct video-microscopic observation of individual nucleation events to obtain time resolved nucleation rate densities. Polarization microscopy and static light scattering on the resulting solids in combination with Avrami theory is used to determine the steady state nucleation rate at high unde…
Towards an Improved Measurement of the Proton Magnetic Moment
2017
The BASE collaboration performed the most precise measurement of the proton magnetic moment. By applying the so-called double Penning-trap method with a single proton a fractional precision of 3.3 parts-per-billion was reached. This article describes the primary limitations of the last measurement and discusses improvements to reach the sub-parts-per-billion level.
Plasma Electron Kinetics and Distribution Functions in Laser Fields
2010
A concise review of the properties of electron distribution functions in a fully ionized plasma in the presence of a high-frequency laser field is presented. In detail is discussed the physical origin of most of the reported results in the case of strong fields. The presence of a laser field, through the inverse bremsstrahlung absorption, alters dynamically the roles of and the interplay between electron-ion and electron-electron collisions shaping the distribution function. Special attention is paid to the role of e-e collisions in the process of laser-plasma interaction.
Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision
2017
Precise knowledge of the fundamental properties of the proton is essential for our understanding of atomic structure as well as for precise tests of fundamental symmetries. We report on a direct high-precision measurement of the magnetic moment μp of the proton in units of the nuclear magneton μN. The result, μp = 2.79284734462 (±0.00000000082) μN, has a fractional precision of 0.3 parts per billion, improves the previous best measurement by a factor of 11, and is consistent with the currently accepted value. This was achieved with the use of an optimized double–Penning trap technique. Provided a similar measurement of the antiproton magnetic moment can be performed, this result will enable…
High-precision measurement of the atomic mass of the electron
2014
A very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus, combined with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics, gives a new value of the atomic mass of the electron that is more precise than the currently accepted one by a factor of 13. The atomic mass of the electron is a key parameter for fundamental physics. A precise determination is a challenge because the mass is so low. Sven Sturm and colleagues report on a new determination of the electron's mass in atomic units. The authors measured the magnetic moment of a single electron bound to a reference ion (a bare nucleus of carbon-12). The results were …