Beta Depth Dose Curves at STUK and PTB: measurements and simulations

Abstract

Depth dose curves from beta radiation sources (90Sr/90Y, 85Kr and 147Pm) of STUK and PTB (BSS2) were measured and compared to each other. Significant differences are obvious for 90Sr/90Y and imply different conversion coefficients from the basic quantity absorbed dose rate to tissue at 0.07 mm tissue depth, Ḋ t(0.07), to the operational quantities Ḣ p(0.07) and Ḣ p(3) for normal (0∘) and oblique (45∘ and 60∘) radiation incidence. The resulting STUK specific conversion coefficients were used to update STUK's measurement results in a recent international comparison measurement (EURAMET 1398) — which now agree significantly better with the corresponding reference values of the comparison. For 85Kr and 147Pm no differences at all between STUK's and PTB's sources were observed. Finally, accompanying radiation transport simulations were undertaken to investigate the difference between STUK's and PTB's 90Sr/90Y beta radiation sources — which could be reproduced by the simulations.