Toward higher-intensity positron beams : investigations in moderation efficiency and beam design

This document discusses investigations into positron moderator efficiency specifically through the use of stacks of etched and annealed tungsten meshes. Flash lamp annealing (FLA) has been shown to be particularly effective for annealing tungsten meshes and FLA enhancement of tungsten meshes may represent the optimal geometry and treatment of tungsten for positron moderation. Design and optimization of the intense pulsed positron beam, the Mono-energetic Positron System (MePS) in Germany are discussed, as are the results of its first experiment investigating low-k materials. Additionally, efforts made toward the creation of a stable, high-intensity positron beam at The University of Texas at Austin through development of the Deflection Focusing Positron Gun (DFPG) are discussed. The DFPG uses a unique geometry and a second moderator for brightness enhancement in order to increase the intensity by at least two orders of magnitude over the typical source-based beam.