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Positronium emission and cooling in reflection and transmission from thin meso-structured silica films

Andersen, SL; Cassidy, DB; Chevallier, J; Cooper, BS; Deller, A; Wall, TE; Uggerhøj, UI; (2015) Positronium emission and cooling in reflection and transmission from thin meso-structured silica films. Journal of Physics B: Atomic, Molecular and Optical Physics , 48 (20) 10.1088/0953-4075/48/20/204003. Green open access

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Abstract

Measurements of the positronium (Ps) energy and formation fraction in reflection and transmission from a thin meso-structured silica target have been conducted using single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy. The silica sample is made using glancing angle deposition of vaporized SiO2 on a suspended thin carbon foil. Optical access through the silica sample facilitates measurement of the longitudinal Ps energy, and the Ps energy in the reflection geometry is found to decrease with positron energy as expected, with a minimum achievable Ps energy of 0.203(12) and 0.26(3) eV for the transverse and longitudinal directions, respectively. In the transmission geometry cooling of Ps becomes evident at the minimum positron impact energy required for the positrons to penetrate the carbon foil and enter the meso-structured silica. The minimum energies for this geometry are 0.210(12) and 0.287(14) eV in the transverse and longitudinal directions, respectively, and the minimum achievable Ps energy is found to be limited by the thickness of the structured silica target, since the same energy was found in both geometries.

Type: Article
Title: Positronium emission and cooling in reflection and transmission from thin meso-structured silica films
Open access status: An open access version is available from UCL Discovery
DOI: 10.1088/0953-4075/48/20/204003
Publisher version: http://dx.doi.org/10.1088/0953-4075/48/20/204003
Additional information: © 2015 IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1477474
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