Investigations into the Optically Stimulated Luminescence Response of Various Materials.

Abstract

Optically stimulated luminescence (OSL) dosimetry involves the illumination of an irradiated sample of an appropriate material to produce a stimulated emission of light whose intensity is indicative of the radiation dose. This technique is currently used for personnel dosimetry, environmental dosimetry and geologic dating applications. While significant research into the OSL behavior of α-Al2O3:C, quartz and feldspar has been published to date, very little information is available about the OSL properties of many other known thermoluminescent (TL) materials. In addition, a thorough, quantitative analysis of the OSL response of α-Al2O3:C to sunlight has not been published in spite of this material being employed worldwide in numerous dosimetry applications. As such, a series of experiments was conducted on the following substances: α-Al2O3:C, CaF2:Mn, Li2B4O7:Cu, LiF:Mg,Ti, KBr, CaSO4:Tm, CaSO4:Dy, CaSO4:Dy+P, LiF:Mg,Cu,Na,Si and LiF:Mg,Cu,Si. The initial experiments used commercially-available OSL readers to investigate several of the materials, to determine which of these materials exhibited OSL behavior to a degree to warrant further investigation, and to inform the design process of a custom-built OSL reader for later experiments. In addition, the sunlight OSL response of α-Al2O3:C was investigated and documented. Once these initial experiments were completed, a custom OSL reader was constructed that would allow the use of additional excitation wavelengths of stimulation light to query samples. Specifically, OSL signals from each material that showed promise in the initial results, as well as some new materials, were measured in response to seven excitation wavelengths from 625 nm to 455 nm, at twelve time periods post-irradiation from 6 h to 120 d. The magnitude and fading behaviors of the OSL response of each material were then analyzed and results documented. Based on these results, it was determined that a significant OSL response exists for CaSO4:Tm, LiF:Mg,Cu,Na,Si and LiF:Mg,Cu,Si. In addition, it was found that the fading rates of OSL signals over time depends upon the excitation wavelength used to elicit the signals, and that these fading rates and the excitation wavelengths that correspond to them correlate well with the TL behavior of the materials.