An in-situ, fiber-optic system for sub-surface, environmental dose measurements using radiophotoluminescence from Ag-doped alkali-phosphate glass

The feasibility of using radiophotoluminescence from Ag-doped alkali-phosphate glass as an in-situ, sub-surface environmental radiation monitor is examined. GD-302M glass from Chiyoda Technol Corporation was attached to the end of a silica optical fiber inside a stainless-steel probe and inserted into soil to a depth of similar to 1 m. Radiophotoluminescence (RPL) from the GD-302M detectors was stimulated along the fiber using a 355 nm pulsed laser and RPL emission was directed along the same fiber and detected by a photomultiplier tube. Restrictions on the average laser power to be used in the experiments were observed due to the creation of an RPL signal for a zero-dose sample, or depletion of the radiation-induced signal from an irradiated sample. Short (1 s), low-frequency (1 kHz) laser stimulation rendered such effects negligible, while providing sufficient sensitivity to enable measurements of environmental doses of similar to 100 mu Gy.