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[en] Positrons, especially slow positron beams, have been expected to be a powerful tool for observation of nature in wide range of research fields from materials science to basic physics, chemistry and biology. At first in this report, methods of slow positron generation are briefly described. The second, research fields and application techniques are reviewed in association with eminent characteristics of positron as a probe of nature. Finally, a direction of positron application is prospected from the viewpoint of combined utilization with other kinds of probes and beams. (author). 71 refs
[en] A reaction microscope that will enable angle-differential positron impact ionisation measurements with atomic and molecular targets, has been recently designed and built to meet the specifications of the Australian Positron Beamline Facility. We present details of this new device, highlighting the modifications to the well-established technique that are required for compatibility with a positron beam, and report on the experimental parameters and detection scheme for the first experiments.
[en] Recent development of the Slow Positron Facility at the Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) is reported. The facility, equipped with a dedicated 55 MeV linac, provides a high-intensity, pulsed slow-positron beam. The beam is produced in a production unit at a high tension of up to 35 kV and guided magnetically through a grounded beam line, and then branched using compact branching units in the experiment hall. An overview, some details of three experiments currently conducted and the outlook of the facility are described.
[en] The positron is the antielectron and annihilates with an electron from the surrounding medium dominantly into two 511 keV γ-rays. The two annihilation γ-rays are modified by the momentum and energy distributions of the electrons in the annihilation site. The annihilation rates are proportional to the electron density in the site. Therefore, the two annihilation γ-rays and the average lifetime of positrons can provide unique informations on a wide variety of problems in condensed matter physics. Slow positrons with narrow energy spread are more useful, compared with white positrons from radioactive isotopes, to the positron annihilation experiment, the low energy positron diffraction, the positron microscope and so on. This review describes the current status and future view on (1) the applications of the positron annihilation to the condensed matter physics, (2) the generation of slow positrons using electron linacs, (3) the positron beam handling system including the pulse stretcher with a Penning trap and (4) the applications of available antiparticles including monoenergetic positrons, muons, pions and antiprotons to the analysis and evaluation of materials, the energy storage and positronium radiations. (author)
[en] The past two years have produced a number of major advances in both theoretical and experimental research on the interaction of positrons with atoms and molecules. This Comment reports on a recent NATO Advanced Research Workshop devoted to this subject. (author)
[en] This note documents a set of expressions used to explore the issue of whether or not it is reasonable to consider a conventional positron source for a Tesla formatted beam. The critical issue is that of energy deposition in the conversion target and the comparison of the induced stress with the ultimate tensile strength of the target material. Since the length of the incident beam pulse is large in comparison to the ratio of beam size to the speed of sound, the concurrent pressure pulse dissipates in a time short compared to the overall pulse duration and one is left with only the semi-static thermal stress. The conclusion of this note is that for tangential target speeds of 100-125 m/s, two positron targets are necessary. For a target speed of 250 m/s, it is possible that a single target can handle to energy deposition. Additional issues that need to be addressed are given at the end. This note is informal in nature
[en] The requirements for, and recent progress toward, the long time confinement of large positron number using a novel micro-trap array will be discussed, with reviews of previously published data highlighted in support of the current proposal. (authors)