SU‐E‐T‐592: OSL Response of Al2O3:C Detectors Exposed to Therapeutic Proton Beams

Abstract

Purpose:To characterize the response of Al2O3:C optically stimulated luminescence (OSL) detectors (OSLDs) exposed to therapeutic proton beams of differing beam quality.Methods:We prepared Al2O3:C OSLDs from the same material as commercially available nanoDot dosimeters (Landauer, Inc). We irradiated the OSLDs in modulated proton beams of varying quality, as defined by the residual range. An absorbed dose to water of 0.2 Gy was delivered to all OSLDs with the residual range values varying from 0.5 to 23.5 cm (average LET in water from ∼0.5 to 2.5 keV/µm). To investigate the beam quality dependence of different emission bands within the OSL spectrum, we performed OSLD readouts using both continuous‐wave stimulation (CW‐OSL) and pulsed stimulation (P‐OSL) with two sets of optical filters (Hoya U‐340 and Kopp 5113). For all readout modes, the relative absorbed dose sensitivity (<i>Srel</i>) for each beam quality was calculated using OSLDs irradiated in a 6 MV photon beam as a reference.Results:We found that the relative absorbed dose sensitivity was highly dependent on both readout mode and integration time of the OSL signal. For CW‐OSL signals containing only the blue emission band, <i>Srel</i> was between 0.85 and 0.94 for 1 s readouts and between 0.82 and 0.93 for 10 s readouts. Similarly, for P‐OSL readouts containing only the blue emission band <i>Srel</i> ranged from 0.86 to 0.91, and 0.82 to 0.93 for 1 s and 10 s readouts, respectively. For OSLD signals containing only the UV emission band, <i>Srel</i> ranged from 1.00 to 1.46, and 0.97 to 1.30 for P‐OSL readouts of 1 s and 10 s, respectively.Conclusion:For measurements of absorbed dose using Al2O3:C OSLDs in therapeutic proton beams, dependence on beam quality was smallest for readout protocols that selected the blue emission band with small integration times.DA Granville received financial support from the Natural Sciences and Engineering Research Council of Canada