SU-E-T-106: Experimental Characterization of Al2O3:C Optically Stimulated Luminescence Detector (OSLD) Exposed to 6 MV X-Ray Beams

Abstract

Purposes: To characterize the response of Al2O3:C optically stimulated luminescencedetectors (OSLDs) to 6 MV x‐ray beams and to determine the optimal bleaching method that would allow the re‐use of the OSLDs. Methods: OSLDs were exposed to a 6 MV x‐ray linac beam in the dose range from 50 mGy–10 Gy. Readouts were performed with a commercial OSLD reader (microStarTM, Landauer Inc.). For 50 mGy and 100 mGy doses, OSLDs were readout using the reader's low‐dose mode, which provides higher stimulation power compared to the high‐dose mode. All other readouts were performed using the high‐dose mode. The OSLD response to dose, bleaching time and repeated readouts (depletion) were determined. Bleaching of the OSL signal was performed using a 250 W halogen lamp with two Methods: (a) direct exposure to light; and (b) exposure using a long‐pass optical filter to block wavelengths shorter than 495 nm. Results: The OSLD dose‐response was linear for the investigated dose range. After 100 readouts, the OSL signal was depleted by (24.5 ± 0.7) % and (3.16 ± 0.07) % with a depletion rate of (0.251 ± 0.002) and (0.023 ± 0.002) %/readout for low‐ and high‐dose modes, respectively. After a 5 min bleaching time, (85.1 ± 1.4) and (70.5 ± 2.0) % reductions in the OSL signal for all doses was attained using methods (a) and (b), respectively. After a 100 min bleaching time, (99.5 ± 0.2) % reduction was attained. Conclusions: We observed linearity of the OSLD's dose response for the investigated dose range. A 100 min bleaching time was sufficient to bleach 99.5 % of the OSL signal for both bleaching methods. The depletion rate using the low‐dose mode is 11 times higher than using the high‐dose mode. for the high‐dose mode of the reader, the depletion rate is independent on dose.