Features of EPR dosimetry with CaSO4:Dy phosphor

The electron paramagnetic resonance(EPR) technique was used to study the paramagnetic centers induced by ionizing radiation in thermoluminescent CaSO4:Dy. Two different radiation induced centers, detectable in the (1–107) Gy dose range and attributed to (SO3)− and Ca–vacancy center, (VCa)2−, respectively, can be used for dosimetry purpose. The (VCa)2− center is detectable only upon sample annealing at temperatures higher than about 180 °C. A reliable dose assessment can be performed in the (1–107) Gy dose range and likely over 107 Gy. The sensitivity decreases with thermal cycles, while the yield of both centers increases with accumulated dose (pumping effect), at a greater extent for (VCa)2− center. (VCa)2− center is stable with time, while (SO3)− center shows a dose-dependent fading. Among the applications that can be imaged for this dosimeter, very high dose assessment capability is of particular importance.