Design and Characterization of a Three-Dimensional Positron Annihilation Spectroscopy System Using a Low-Energy Positron Beam

Previous forays by AFIT into positron research have resulted in the development of a new positron annihilation spectroscopy PAS technique and the procurement of a low-energy positron beam system. The primary purpose of this research was to design and build a state-of-the-art PAS laboratory at AFIT capable to address a myriad of DoD solid-state and surface physics questions. The main objectives were to acquire and assemble utilities to operate a positron beam, assemble and con gure an ultra-high vacuum UHV system for samples, design and build an interface with a magnetic eld to propagate positrons onto samples, and create a new version of the three-dimensional positron annihilation spectroscopy system 3DPASS. The 3DPASS, which measures coincidence Doppler broadening of annihilation radiation CDBAR and two-dimensional angular correlation of annihilation radiation 2D-ACAR, was characterized using a Cu-22Na positron annihilation source made as part of this project. Integration of the 3DPASS with low-energy positron beam will allow for energy-dependent, nondestructive characterization of materials using PAS.