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Showing 1 to 20 of 55 for “"positrons"”.
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Cold trapped positrons and progress to cold antihydrogen
… allowing us to trap equal numbers of either positrons or electrons over a wide range of conditions. Antiprotons are trapped, cooled, and stacked from the new Antiproton Decelerator facility for the first time. Combining positrons and antiprotons, we have demonstrated the first positron …
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Some effects on polymers of low-energy implanted positrons
… materials because a defined penetration depth of positrons can be obtained. This thesis is focused on two issues: 1. The median penetration depth of positrons z1/2(E), related to the positron implantation profile is assumed to be a power-law z1/2(E)= (α/ρ)En. Here ρ is the sample density and the …
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Scattering of High Energy Positrons and Electrons; Large Angle Pair Production by Bremsstrahlung
Made available in DSpace on 2015-05-12T17:12:05Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 0020878.PDF: 8599885 bytes, checksum: fb3323d99f23f186e22cdd360b92e64b (MD5) Previous issue date: 1957
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Higher-order effects in the elastic scattering of electrons and positrons from lead-208 and carbon-12
… scattering cross sections of electrons and positrons from $\sp{12}$C and $\sp{208}$Pb, in an effort to observe and quantify deviations from the predictions of a phase shift calculation of the scattering from a static charge density. Any deviations observed can be attributed to higher-order …
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Contribution aux méthodes de reconstruction d'images appliquées à la tomographie d'émission par positrons par l'exploitation des symétries du système
… théorique maximale en tomographie d’émission par positrons (TEP) sont à nos portes. Pour retirer le maximum d’information de ces appareils, il importe d’utiliser des méthodes de traitement évoluées qui prennent en considération l’ensemble des phénomènes physiques entourant la prise de mesure en …
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Annihilation des positrons dans les métaux de sodium et de potassium, sous l'effet d'une pression hydrostatique: thèse
Des mesures de vie moyenne ont été effectuées sur des échantillons de sodium et de potassium • Ces mêmes échantillons étaient soumis à des pressions hydrostatiques variant de la pression atmosphérique jusqu'à une pression maximum de 55 kilobars. Compte tenu de certaines difficultés techniques dans …
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ATRAP Buffer-Gas Positron Accumulator
… methods require large numbers of antiprotons and positrons (the constituent particles of antihydrogen). This dissertation describes the methods developed to increase the number of positrons available for the ATRAP experiments by a factor of 200. The development of the new positron loading scheme …
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A measurement of the magnetic field systematic correction to the muon anomalous magnetic moment associated with muon phase space in experiment BNL E821
… into a magnetic storage ring and decay into positrons via the parity violating weak interaction. The spin precession rate of the muons in the ring is then determined by measuring energy oscillations of the decay positrons. The rate of oscillation is directly proportional to the magnetic …
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Low Energy Positron Interactions With Biological Molecules
… density distribution which can be used for positrons bound to midsize and larger molecules have been tested for smaller molecules and subsequently applied to investigate the most likely e+e- annihilation sites for positrons interacting with biological molecules containing C, H, O, and N. In …
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Studies in positron and gamma ray production for future facilities
… However, producing a sufficient numbers of positrons is a significant challenge. One of the most difficult problems associated with the production of positrons is designing a production target that will survive in an intense photon beam while rotating at high speeds to spread out the energy …
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On The Origin of Super-Hot Electrons in Intense Laser-Plasma Interactions
… the generation of relativistic electrons and positrons was performed at the Texas Petawatt laser which resulted in the observation of the highest known positron energies ever recorded. The positrons are created by the Bethe-Heitler process where an electron scatters and emits bremsstrahlung …
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Dark Matter Annihilation and the Observed Positron Excess
… experiments, PAMELA and Fermi, show a flux of positrons above the expected background signal; this positron excess may point toward a primary source of positrons that could be explained by dark matter annihilations. Utilizing DarkSUSY to generate supersymmetric models in which the neutralino is …
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Design of a positron beam for the study of the entanglement in three gamma-rays generated by positronium annihilation
… positron with pair production. In fact, the positrons are the most available antiparticle in the universe, the characteristic 511keV annihilation photons have been observed in active galactic nuclei [1], in the sun [2], and even in thunderstorm clouds on Earth [3]. The antiparticles are not …
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Novel designs for undulator based positron sources
… linear colliders require a high ux of positrons. To achieve this a number of new positron source designs have been proposed. One of these is an undulator-based positron source, which is the baseline positron source design for the International Linear Collider. The undulator-based …
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Asymmetric Positron Annihilation in Chiral Tartrate and Tartaric Acid Crystals
… has been used to study the interactions of positrons with chiral tartaric acids and tartrates. Differences in lifetimes of and its intensity I2 were compared between large crystals grown from the D- and L- enantiomers of sodium ammonium tartrate and tartaric acid. A tentative but statistical …
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A transition radiation detector and gas supply system for AMS
… positron spectrum. A 10-6 separation of positrons from the more abundant protons is planned for this signal. A TRD (Transition Radiation Detector) has been designed to achieve these physics goals. Besides the radiator, the TRD is a gaseous detector that needs a gas system providing signal …
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Novel Schemes for the Collimation of Neutral Electron-Positron Beams
… instabilities occur between the electrons and positrons as they interact with the interstellar medium. This causes the electrons and positrons to filament out into separate beam-lets that set up strong magnetic fields between them. What drives the micro-physics behind such phenomena is still a …
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Diagnostics of solar flare energetic particles: neglected hard X-ray processes and neutron astronomy in the inner heliosphere
… show the presence of 100 MeV electrons and positrons in the solar corona, by-products of GeV energy ions. We present results of ICS of solar flare photons taking proper account of radiation field geometry near the solar surface. If observed, such radiation would let us determine the number …
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Modeling the affect of dark matter distributions in the Milky Way on the component of the cosmic rays energy spectrum as incident on Earth
… as the annihilations which convert them into positrons. We then channeled the results into a galaxy propagation software package GALPROP and obtained a positron spectrum on earth. Our results suggest that while no dramatic differences emerge in the spectrum as a result of varying dark matter …
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