Optimizing the moderator geometry and thickness for a reactor-based slow positron source

•10 μm thick tungsten foils maximize the yield of thermal positrons.•A tradeoff exists between total thermal positron yield and extraction efficiency.•Narrow moderator grids are more efficient at higher extraction potentials.•Reflection survival probability significantly affects extraction efficienc...

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Bibliographic Details
Published in:Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2021-06, Vol.497, p.39-46
Main Authors: Alsulami, Raed, Albarqi, Mubarak, Jaradat, Safwan, Usman, Shoaib, Graham, Joseph
Format: Article
Language:English
Subjects:
Nuclear reactor
Positron moderator
Slow positrons
Tungsten
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Summary:•10 μm thick tungsten foils maximize the yield of thermal positrons.•A tradeoff exists between total thermal positron yield and extraction efficiency.•Narrow moderator grids are more efficient at higher extraction potentials.•Reflection survival probability significantly affects extraction efficiency. Monte Carlo radiation transport simulations were used to calculate the slow positron yields from tungsten foil positron moderators at a reactor-based slow positron source. The slow positron generation rates were coupled to a simple electrostatic extraction model to estimate the yield of extractable slow positrons from the source. These calculations were used to optimize the foil thicknesses, length, pitch, and extraction voltages.
ISSN:0168-583X
1872-9584
DOI:10.1016/j.nimb.2021.04.005