Date of Award

3-21-2013

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Larry W. Burggraf, PhD.

Abstract

Previous endeavors in positron annihilation spectroscopy (PAS) at AFIT have resulted in the design and characterization of a second-generation three-dimensional positron annihilation momentum spectroscopy system (3DPAMSS) which combines two-dimensional angular correlation of annihilation radiation (2D ACAR) and coincident Doppler broadening of annihilation radiation (CDBAR) in order to measure electron momentum distributions in samples and thus characterize material defects. The focus of this particular research is to nondestructively measure negative defects in the crystal lattice of copper-doped, silver-doped, and undoped lithium tetraborate by 3DPAMSS spectroscopy using a Na-22 source and two high-purity germanium (HPGe) position-resolvable strip detectors. Lithium tetraborate is a candidate material for novel neutron detectors and characterizing its crystal structure is necessary to fully understand its properties. Several angular deviation and differential energy features are noted, which are translated to potential electron momentum distribution features and crystal defect characteristics.

AFIT Designator

AFIT-ENP-13-M-09

DTIC Accession Number

ADA584589

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Nuclear Commons

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