SCINTILLATION CRYSTAL HAVING REDUCED AFTERGLOW AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To reduce or eliminate afterglow by adding a particular afterglow reducing additive of proper concentration into a crystal melt. SOLUTION: Cobalt-doped cadmium tungstate ball seems to have wide range absorption in the wave length range of 540nm to 700nm. The cobalt-doped ball also has lower light output than the undoped ball of the same green material. Reducing the quantity of cobalt in cadmium tungstate leads to reduce the quantity of light absorbed by it and increase its light output. By controlling the cobalt quantity, it is possible to make crystal having light output over 90% of the light output of undoped crystal and afterglow reduced for 5 times or more. The concentration of cobalt in the melt varies between 10 to 50ppm, and however, actual concentration of cobalt in doped crystal was fairly less because of natural trend of crystal lattice to avoid dopants during the growth.