Ultra-intense laser interactions with solid foils are studied as a means to produce relativistic positron plasmas, which has been proposed as a potential laboratory for understanding positron-electron plasma aspects of gamma-ray bursts [1]. Initial experiments with high energy Nd:glass lasers have revealed a strong dependence of the positron yield, and energy distribution, on the thin-foil targ...

Positron thermalization in Si and GaAs has been studied both by experiments and simulations. The decrease in the positron mean energy due to the interactions with longitudinal-acoustic phonons was calculated down to 4 K by solving numerically the Boltzmann equation for the positron momentum distribution. We find that the differences in the strength of the positron-phonon coupling can result in ...

Recently INTEGRAL/SPI has observed a strong and extended emission resulting from electron-positron annihilation in the Galactic center region, consistent with the Galactic bulge geometry. The positron production rate, estimated to more than 10 per second, is very high and raises a challenging question about the nature of the Galactic positron source. Commonly considered astrophysical positron i...

BACKGROUND Revascularization of patients with ischemic heart disease and poor left ventricular function for surgical procedures is expensive and carries considerable risks, but may improve survival for patients with hibernating myocardium. Positron emission tomography can detect hibernating myocardium, and may be cost-effective if used to select patients for operation. METHODS An economic mod...

The full exploitation of the physics potential of an International Linear Collider (ILC) requires the development of a polarized positron beam. New concepts of polarized positron sources are based on the development of circularly polarized photon sources. The polarized photons create electron-positron pairs in a thin target and transfer their polarization state to the outgoing leptons. To achie...

In the TESLA linear collider, two interaction regions are foreseen, one for ee collisions at zero crossing-angle, and the other one for ee , e e or collisions at about 40 mrad crossing angle. Beam switchyards must therefore be designed after the electron and positron(or electron) linacs to switch the electron and positron (or electron) beams and serve the two interaction regions. On the electro...

Abstract First-principles approaches based on density functional theory (DFT) for calculating positron states and annihilation characteristics in condensed matter are presented. The treatment of electron-positron correlation effects is shown to play a crucial role when calculating affinities and annihilation rates. A generalized gradient approximation (GGA) takes the strong inhomogeneities of t...

Positron range is one of the main physical effects limiting the spatial resolution of positron emission tomography (PET) images. If positrons travel inside a magnetic field, for instance inside a nuclear magnetic resonance (MR) tomograph, the mean range will be smaller but still significant. In this investigation we examined a method to correct for the positron range effect in iterative image r...

We present total, elastic, and inelastic cross sections for positron and electron scattering from tetrahydrofuran (THF) in the energy range between 1 and 5000 eV. Total cross sections (TCS), positronium formation cross sections, the summed inelastic integral cross sections (ICS) for electronic excitations and direct ionization, as well as elastic differential cross sections (DCS) at selected in...

We report a positron annihilation study using state-of-the-art experimental and theoretical methods in n-type semi-insulating β-Ga2O3. utilize the recently discovered unusually strong Doppler broadening signal anisotropy of β-Ga2O3 orientation-dependent measurements, complemented by temperature-dependent lifetime experiments first principles calculations positron–electron signals. find that spl...