Year
2001
Abstract
Optically Stimulated Luminescence (OSL) technology has been pioneered at the Pacific Northwest National Laboratory (PNNL) for applications in personnel radiation dosimetry and has become highly successful commercially in replacing older technologies such as Thermoluminescence Dosimeters (TLDs) and film. OSL phosphors are used to measure ionizing radiation exposure by illuminating the phosphor with light and measuring the amount of light emitted. The light emitted by the OSL phosphor is directly proportional to the radiation exposure received. By using a twodimensional plate of OSL material and raster scanning a light beam across the OSL plate a radiation pattern or image can be measured. The Arms Control community may find it desirable to use an electronics-free medium to measure certain attributes, such as the extent and symmetry of Pu pits in storage containers. OSL technology, used in the two-dimensional imaging mode, provides a means to measure these attributes with exposure times on the order of an hour. A special OSL reader has been built by PNNL to measure OSL imaging plates with a size of 20 cm by 30 cm. The reader uses 10 light emitting diode clusters with 10 corresponding photomultiplier tubes to measure an OSL imaging plate in less than 5 minutes. The resolution of each of the 10 measurement assemblies is 1 square-centimeter. An collimator assembly employing a Venetian-blind type collimator is used in conjunction with the OSL film to image the Pu pit within the storage container. The output of the OSL reader is a two-dimensional array of intensities that will be used with the appropriate information barriers to measure extent and symmetry. This device also clearly distinguishes the difference between a point source and a distributed source. Details of the OSL technology, OSL reader system, collimator design, and system performance will be presented.