Radioluminescence (RL) probe dosimetry using Al2O3:C for precise calibration of beta sources applied in luminescence dating

The radioluminescence (RL) phenomenon is widely known as prompt luminescence or fluorescence of synthetic materials, like Al2O3 and LiF as well as of natural dosimeter materials, like feldspar and quartz, during interaction with ionising radiation, especially electron rays. Almost all of these materials show increasing RL flux with increasing absorbed beta dose. Only potassium rich feldspars (microcline and orthoclase) show a RL emission at 1.45 eV of decreasing intensity with rising delivered dose. For a number of reasons, this RL emission is suitable for dating purposes. Accuracy and reproducibility of the RL dating method are much more advantageous compared to TL and OSL methods. Carbon doped Al2O3 (TLD 500) shows a much more higher RL intensity than, e.g., feldspar and the stability of the stored electrons as well as the linearity of RL yield versus primary electron energy, qualifies this dosimeter material to be a useful tool in source calibration, using radioluminescence. However, the accuracy of a luminescence dating method depends largely on the calibration of the used irradiation sources. To prevent calibration uncertainties due to the use of natural dosimeters with a high scattering of luminescence yield, a new method is suggested. This method bases on probe dosimetry using a very small amount of Al2O3:C as probe and, consequently, the material that should be calibrated (e.g. feldspar). The amount of Al2O3:C may disturb the electron fluence within the material to be calibrated only insignificantly. The sample mix is irradiated by an exactly known Gamma or Beta radiation source and the absorbed dose is treated as absorbed dose in the appropriated material. In contrast to conventional calibration methods, the suggested performance uses the dose dependent RL signal of Al2O3:C at 3.00 eV. This shows a good reproducibility, even with a tiny amount of the applied synthetic probe material. (author)