Date of Award

Spring 2004

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor

Seitz, Martin A.

Second Advisor

Fournelle, Raymond A.

Third Advisor

Hirthe, Richard W.


Cadmium Tungstate crystals are widely used as single crystal detector arrays for Computer Tomography (CT) scanners in medical diagnostics and explosive detection systems for inspection of luggage and air cargo. Cadmium Tungstate (CdW04) is a colorless oxide crystal which is grown at 1240°C by Czochraslki techniques. The light output is 30% of the relative output of Csl: Tl, but is adequate for CT scanners at current throughput and its afterglow are the lowest among the materials used in these detectors. Recent developments in the growth techniques of CdW04 have reduced the radiation damage susceptibility but have failed to improve its light output. These include the minimization of impurity defects and reduction of Cd vacancy defects by replacement of the CdO evaporated during high temperature growth. Extensive doping of the crystal to improve properties such as radiation damage and light output has not been accomplished, most likely due to difficulties in uniformly doping the single crystals. The research outlined here, investigates a target scintillator which has the attributes of CdW04 with improved light output greater than 50% relative to Csl: Tl crystal's Relative Light Output and investigates crystal doping processes to improve radiation resistance while maintaining the favorable afterglow characteristics of CdW04. The increased light output will dramatically reduce the X-ray dose levels required to performed medical diagnostic procedures and will allow for deeper penetration, improved imaging of concealed packages and shielded objects and improved system throughput of diagnostic procedures and security inspections of concealed explosives.



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