MRI: Development of a Confocal Instrument for Spatially Resolved Luminescence Measurements in Geologic and Archaeological Dating and Radiation Dosimetry

来自主要研究仪器（MRI）项目的资金将支持俄克拉荷马州立大学用于空间分辨光激发发光（OSL）测年的共聚焦仪器的开发。该仪器将支持沉积学/地层学和考古学研究，这些研究依赖于对不可能采用其他地质年代学技术的天然和人造材料进行定年（例如，对没有有机物进行放射性碳定年的第四纪冰川漂流碎屑、河流阶地砾石、海滩巨石、砂浆进行定年）。光激发发光（OSL）测年可以通过测量样品在实验室辐照过程中发出的发光来确定沉积时间（沉积物最后一次暴露在阳光下的日期）。太阳光通过释放积聚在光敏晶体缺陷处的被困电子而使发光归零。发射光的强度（OSL信号）与自埋藏以来吸收的辐射剂量成正比，从而可以计算自沉积以来的时间。商业上可用的发光读取器和技术仅限于单个矿物颗粒小于几毫米的样品，这使得该方法无法应用于岩石等大块材料，这就排除了许多地质和考古样品。开发的共聚焦光光显微镜将允许全自动化，微米尺度的空间分辨率光光测年超过景深。该仪器将把OSL测年技术的应用范围扩大到大于几毫米的固体样品，从而使该技术能够应用于许多以前无法确定的沉积物，如砾石海滩、辫状河和冲积扇的沉积物。同样的年代测定技术也可用于确定具有重要考古意义的建筑物的建造或破坏日期，而目前只能通过测定周围沉积物的年代来确定。该仪器还将允许进行空间分辨剂量测量，从而提供有关环境辐射剂量率微观变化的信息，从而提高传统OSL定年技术的准确性。该仪器将是世界上第二种共聚焦光学光学仪器，也是美国的第一种。俄克拉何马州立大学的学生将获得一个独特的机会，获得物理学、工程学以及地质学和考古学的跨学科经验。

Funds from this Major Research Instrumentation (MRI) Program grant will support development of a confocal instrument for spatially resolved optically stimulated luminescence (OSL) dating at Oklahoma State University. The instrument will support sedimentological/stratigraphic and archaeological research that relies on dating of natural and man made materials where no other geochronologic technique is possible (e.g., dating of Quaternary glacially rafted debris where no organics are available for radiocarbon dating, fluvial terrace gravels, beach boulders, mortars). Optically stimulated luminescence (OSL) dating allows for establishment of time of deposition (date of the last sunlight exposure of sediments) through the measurement of luminescence emitted from the sample during irradiation in the laboratory. Sunlight zeroes out luminescence by releasing the trapped electrons that accumulate at light sensitive crystal defects. The intensity of the emitted light (the OSL signal) is proportional to the radiation dose absorbed since burial, allowing calculation of time since deposition. Commercially available luminescence readers and techniques are limited to samples with individual mineral grains smaller than a few millimeters, preventing application of the method to bulk materials such as rocks, which excludes many geological and archaeological samples. The developed confocal OSL microscope will allow for fully automated, micron-scale spatial resolution of OSL dating over the depth of field. The instrument would expand the application breadth of OSL dating technique to solid samples larger than a few mm and therefore allow the technique to be applied to many previously undatable deposits such as those from gravel beaches, braided streams, and alluvial fans. The same dating technique may be used for determination of the construction or destruction date of archeologically significant buildings, which presently is only possible by dating the surrounding sediments. The instrument will also allow for spatially-resolved dose measurements that could provide information on microscopic variations in the environmental radiation dose rate and therefore improving the accuracy of the conventional OSL dating technique. The instrument will be the second confocal OSL instrument in the world and the first in the United States. Students at Oklahoma State will be afforded a unique opportunity to gain interdisciplinary experience in physics and engineering as well as geology and archaeology.