Is Kapton * Really That Simple?

Age momentum correlation experiments in kapton has revealed the existence of two positron states corresponding to the trapping of positrons on the partially negatively charged O and/or N sites in the polymer chain. A young age broadening of the annihilation line shape is also observed and is attributed to the annihilation in flight of the positrons

AEGIS at CERN: Measuring Antihydrogen Fall

The main goal of the AEGIS experiment at the CERN Antiproton Decelerator is the test of fundamental laws such as the Weak Equivalence Principle (WEP) and CPT symmetry. In the first phase of AEGIS, a beam of antihydrogen will be formed whose fall in the gravitational field is measured in a Moire' deflectometer; this will constitute the first test of the WEP with antimatter.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 201

Proposed antimatter gravity measurement with an antihydrogen beam

The principle of the equivalence of gravitational and inertial mass is one of the cornerstones of general relativity. Considerable efforts have been made and are still being made to verify its validity. A quantum-mechanical formulation of gravity allows for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction of matter and of antimatter should be identical, this assertion has never been tested experimentally. With the production of large amounts of cold antihydrogen at the CERN Antiproton Decelerator, such a test with neutral antimatter atoms has now become feasible. For this purpose, we have proposed to set up the AEGIS experiment at CERN/AD, whose primary goal will be the direct measurement of the Earth's gravitational acceleration on antihydrogen with a classical Moiré deflectometer. © 2007 Elsevier B.V. All rights reserved

Using a Bent Tube as an Energy Filter for a Positron Beam. Simulations on Determining the Optimum Angle of the Bend

One way to perform lifetime measurements at a DC positron beam is to pass positrons through a pulsing device. The compressed e⁺ bunches are accelerated to a desired energy for depth profiling of the studied sample. A fraction of the e⁺ that are backscattered from the sample surface can travel back through the uniform magnetic field that is generated along the central axis of the beam transport lines and reach the accelerator. The backscattered e⁺ that reach the accelerator can be re-accelerated towards the sample and re-implant in it with a delay from the initial implanted e⁺ bunch. These e⁺ that are re-implanted into the sample with a delay cause distortions in the lifetime spectra. A setup which uses a bent tube to act as an energy filter to reduce the effect of the backscattered e⁺ is studied by simulations. The simulations are performed in order to find the optimum geometry for minimum distortions

Using a Bent Tube as an Energy Filter for a Positron Beam. Simulations on Determining the Optimum Angle of the Bend

One way to perform lifetime measurements at a DC positron beam is to pass positrons through a pulsing device. The compressed e⁺ bunches are accelerated to a desired energy for depth profiling of the studied sample. A fraction of the e⁺ that are backscattered from the sample surface can travel back through the uniform magnetic field that is generated along the central axis of the beam transport lines and reach the accelerator. The backscattered e⁺ that reach the accelerator can be re-accelerated towards the sample and re-implant in it with a delay from the initial implanted e⁺ bunch. These e⁺ that are re-implanted into the sample with a delay cause distortions in the lifetime spectra. A setup which uses a bent tube to act as an energy filter to reduce the effect of the backscattered e⁺ is studied by simulations. The simulations are performed in order to find the optimum geometry for minimum distortions

Effect of Annealing on Free-Volume Properties of Poly(ethylene Terephthalate) Studied by Positron Annihilation

The effect of annealing on free-volume properties of poly( ethylene terephthalate) was studied using a set of samples annealed for two hours in air at eight temperatures between 80ºC and 220ºC. The fractional free-volume in the samples was estimated from ortho-positronium lifetime and its relative intensity. The variations of fractional free-volume and of the macroscopic specific volume with annealing temperature were compared. The variation of the pore volume probability density functions with the annealing temperature was found. The interdependence between S- and W-parameters was also discussed

Pore closure in spark plasma sintered alumina studied by variable energy positrons

The porosity type in spark plasma sintered alumina was studied by variable energy positron beam technique. The gamma ray energy spectra of interest in the region of the annihilation peak were analyzed by means of Compton-to-peak ratio and deconvolution into Gaussians of the Doppler broadened annihilation peak. The contributions of the two narrow Gaussians (centered and red-shifted) revealed difference in the porosity type according to the heating rate. The samples sintered at low heating rate showed open porosity. Closed porosity appeared at 1050 °C as a result of formation of isolated pores. For the samples sintered at high heating rate, closed porosity was found to be significant even at comparatively low sintering temperatures which was explained by a blocking effect at the sample free surface