Date of Award

3-21-2013

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Robert Hengehold, PhD.

Abstract

The Department of Defense is interested in lithium tetraborate (Li2B4O7) crystals for their possible use as a solid state neutron detection material. With large concentrations of 6Li and 10B, it has a high neutron capture cross section. Furthermore, the crystal fluoresces in the presence of ionizing radiation, making it an attractive candidate for a scintillating detection device. However, there is a lack of fundamental knowledge about the material characteristics, particularly with regard to its fluorescent spectrum. Cathodoluminescence measurements were conducted on undoped and doped samples of lithium tetraborate in order to characterize the nature of its fluorescent spectra under different environmental conditions. Measurements were made using a vacuum ultraviolet cathodoluminescence system specifically designed to detect high energy photons emitted in wide band gap materials. The cathodoluminescent spectra from 10 K to room temperature was characterized for six different lithium tetraborate crystals: three undoped crystals and one each doped with silver, copper, and manganese. Thermoluminescence measurements were conducted using a Harshaw Model 3500 Manual TLD Reader. After electron irradiation from the cathodoluminescence experiment, the samples were heated from 50 °C to 250 °C at a heating rate of 1 °C per second. The thermoluminescence measurements provided insight into the carrier trapping ability of the crystals after electron irradiation.

AFIT Designator

AFIT-ENP-13-M-13

DTIC Accession Number

ADA584348

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