| Popis: |
The objective of the present work was to develop and validate a computational model of the Beta Secondary Standard type 2 (BSS2) system, with sources, filters and the PTW 23392 extrapolation chamber using MCNPx code. Simulations were performed to calculate the absorbed dose rate to tissue at null depth and 0.07 mm for the 85Kr, 90Sr/90Y and 147Pm beta radiation sources. The response curve was calculated by computing the energy deposited, at different depths, to the sensitive volume of the chamber. The deviations in the absorbed dose rate obtained using the MCNPx code compared to the calibration certificate data were found to be up to 2 %. Deviations up to 10 % were observed for the transmission factor calculated for all three beta sources. This work describes in detail the main parameters and common issues seeing when modelling an extrapolation chamber and three different beta standard sources. |
