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A new positron source with high flux and excellent electron-optical properties

✍ Scribed by Manfred Fink; Hermann Wellenstein; Scott V. Nguyen


Publisher
Elsevier Science
Year
2007
Tongue
English
Weight
445 KB
Volume
261
Category
Article
ISSN
0168-583X

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✦ Synopsis


Positron annihilation spectroscopy is a well established research tool to study the surface and bulk electron distributions of solids and liquids. These are extracted from the energy and angular distributions of the two 511 keV X-rays, produced during the annihilation of a thermal positron and an electron from the sample. Positron investigations and monitoring, however are currently not used in an industrial environment due to the lack of a sufficiently intense positron sources to record distribution functions with good statistics within minutes. Most positron spectrometers have radioactive sources which produce only modest intensities (10 6 e + /s). An improvement by at least a factor of 100 is needed to become viable for on-line positron metrology. We propose to combine several technologies to generate a positron beam with good electron-optical properties, such as a small divergence angle and small beam diameter and a flux of 10 8 e + /s or more. Positrons from a 10 Ci beta source will be moderated with a stack of 12 layers of tungsten meshes. The thermalized positrons will be accelerated into a deflection focusing analyzer (DFA) which focuses the positrons into a small (1-2 mm 2 ) area of a second moderator. A rare gas solid will be used to thermalize the positrons once more. The moderating area forms the small emitter source for a accelerating gun that generate a beam of mono-energetic positrons of any desired energy.


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