|Student Name:||Maj Douglas A Buchanan|
|Thesis:||EPR AND ENDOR STUDIES OF POINT DEFECTS IN LITHIUM TETRABORATE CRYSTALS|
|Location:||ENP Conference Room (Bldg 640 Rm 217)|
|Date & Time:||11/05/2012 at 1300|
|Abstract:|| Lithium tetraborate (LTB) is a promising material for both radiation dosimetry and neutron detection applications. Research in this dissertation focuses on undoped LTB crystals and LTB crystals doped with copper or silver. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are the primary experimental techniques used in this dissertation to characterize the point defects in the crystals. Thermoluminescence (TL), photoluminescence (PL), photoluminescence excitation (PLE), and optical absorption (OA) are also used. An intrinsic hole trap associated with lithium vacancies is characterized. A "perturbed" hole trap due to Ag2+ ions is characterized in doped crystals using EPR data alone. This method is also successfully applied to a previously studied Ag2+ hole center where both EPR and ENDOR were used for characterization. New x-ray induced centers are identified in copper-doped crystals. These centers are characterized with EPR and their thermal stability explains previously observed TL peaks. Finally, a comprehensive study utilizing EPR, OA, PL, and PLE data provides convincing explanations for the absorption and emission features of silver-doped crystals.