Monte carlo modelling of 90sr/90yand 85kr beta fields for hp(3) measurements

In support of research aimed at developing a thermoluminescence dosemeter capable of accurately measuring ionising radiation doses to the lens of the eye, Monte Carlo modelling of a standard beta exposure set-up has been performed. It was found that electrons with an energy distribution corresponding to the beta emission spectrum from 85Kr deposit negligible doses at a depth of 3 mm in tissue, but doses from 90Sr/90Yare significant; free in air and fluence-to-Hp(3,u8) and -Hp(0.07,u8) conversion coefficient data were found for this field for exposures at 08, 308 and 608 angles of incidence, and the response characteristics of the new eye dosemeter were evaluated. It was shown that the results were not affected greatly by the shape of the calibration phantom. However, it was demonstrated that the presence of intermediating air and beam flattening filters hardens the energy distribution of the field at the point of test, relative to a raw 90Sr/90Y source, and this impacts dose depositions.