Depth dose curve and surface dose measurement with a μm thin dosimetric layer
In a former work inorganic phosphor particles NaYF4:Yb3+, Er3+ were found to exhibit a radiation dose dependency of their luminescence decay time upon near-infrared excitation. This material is now presented in the form of an ultra-thin dosimeter to measure depth dose curves. They were derived by electron beam irradiation of 1.6 mm thin dosimeters through a stepped stack of absorber polymer films followed by optical decay time evaluation. The suitability of the phosphor dosimeters for depth curve measurement is proven by good agreement in normalized dose results with film dosimeter (Risø B3 strips) after medium-energy electron-beam irradiation. But the approach qualifies especially for use at low-energies, where original measurement results from as close as 3-4 mm (water equivalent) from the surface are obtained for 80, 140 and 200 keV e-beam irradiations. They align well with results from Monte Carlo simulations. Thus, an approach is proposed for discussion which may allow the experimental evaluation of the first mm of depth dose curves after low-energy electron beam irradiation.