The effect of external regeneration on the performance of CaSO4:Dy discs

The authors have investigated the effect of annealing on the reproducibility of CaSO4: Dy dosimeters. The dosimeters cannot be used without external thermal treatment in high precision therapy level dosimetry while a 600 degrees C-1 h external regeneration resulted in a better reproducibility than a 400 degrees C-1 h treatment (which may be used if the absorbed dose in water does not exceed a few Gy). The background of the dosimeters increased considerably even in a 10 X 1 mGy exposure as a result of irradiation history if no external regeneration was used.