Evaluation of aluminum oxide fluorescent and OSL detectors in proton radiotherapy beams

Fluorescent Nuclear Track Detectors (FNTD) and Optically Stimulated Luminescence Detectors (OSLD) were investigated for application in proton therapy dosimetry. FNTDs and OSLDs are made of Al 2O 3:C,Mg single crystals and Al 2O 3:C powder, respectively. The detectors were irradiated in water, behind different thicknesses of plastic slabs and behind wedge shaped plastic absorbers. FNTDs positioned behind different thicknesses of plastic slabs and in water phantom show Bragg curves with a peak to entrance ratio of eight compared to about three from ionization chamber measurements. The over-response of FNTDs is attributed to the non-linear response of the power spectrum integral (PSI) parameter as a function of proton linear energy transfer (LET). The limitations of the wedge absorber experiment due to lateral proton straggling are discussed. Experimental data and image simulations were utilized to obtain LET dependencies for the FNTD power spectrum integral and fluorescence amplitude.