Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Benjamin R. Kowash, PhD.


The timing properties of BCF-12 scintillating plastic fibers arranged in a coherent bundle are investigated. An MCNP transport model is developed analyzing the interaction of neutrons with fiber bundles of varying size. A gradient in energy deposition is seen starting at the 10x10 fiber bundles onward. A 40x40 bundle has 6.7 ± 0.2% intrinsic efficiency for double scatter events. Over 40% of the double scatter events occur with a time separation of 1 ns or greater in the 40x40 bundle. The lowest dark count rate was achieved with the lens cap / aluminum can and collar system with a dark count rate of 15 per second. A bimodal distribution of scintillation pulse decay constants is discovered; these two distributions are statistically different from each other allowing real-time discrimination of dark events from scintillation events using a single PMT. A dual-ended readout technique is used to investigate scintillation pulse shapes. No significant difference is measured between the multiple peaks seen in scintillation pulses of single fibers and fiber bundles. Multiple scatter events were not detected using a 7x3 fiber bundle. Construction of a 40x40 fiber bundle is recommended for future research due to its intrinsic efficiency and measurable double-scatter event probability.

AFIT Designator


DTIC Accession Number