Progress in 2D-OSL-dosimetry with beryllium oxide

Abstract

Abstract The 2D-OSL system, previously described by Jahn et al. (2010) , was enhanced. Two methods of stimulation and OSL-detection were evaluated. Using single fiber stimulation the blue stimulation light of a LED was inserted into a fiber. With the help of a focuser a spot of 0.5 mm diameter on the detector was stimulated. OSL reading was performed by a photosensor module from the opposite detector side. With the help of a 2D axial system BeO area detectors (Thermalox 995 – 52 mm × 52 mm × 1 mm) were positioned between the stimulation element and the photosensor module. A line-by-line scanning gave information about the dose distribution in the detector. Evaluated spatial resolution is approx. 1 mm. Due to more intensive stimulation by the focusing of LED light the evaluation time could be decreased to 10 min for an area of 52 × 52 mm 2 which is suitable for scientific applications. For medical applications the speed has to be increased. Therefore a prototype, the multifiber array was tested. It offers the ability to evaluate a line of 4 mm by the use of 8 fibers for stimulation and 8 fibers for OSL-detection with a pitch of 0.5 mm. So the line could be measured without any detector movement. Spatial resolution is better than using single fiber stimulation, measurement time for an area detector could be decreased by a factor 5. The use of multifiber arrays with more than 8 fibers offers fast detector scanning, so appliance in medicine would be possible. The dosimetric properties of the BeO area detectors were consistent with the smaller detectors (Thermalox 995 – 4.7 mm × 4.7 mm × 0.5 mm) examined by Sommer et al., (2007) . So, with both methods, 2D-radiation fields could be monitored. One example, the imaging of several absorbers, is shown.