Investigation of the energy response of thermoluminescence dosimeter used for measurement of individual dose-equivalent

One of the challenges of individual dosimetry in Iran is the absence of standard radiation fields with different energies for calibration. For dosimetry in the photon fields, only the standard fields of Co-۶۰ and Cs-۱۳۷ sources, located in the (SSDL) can be utilized. This study aims to determine energy response of a personal thermoluminescence dosimeter (TLD) designed for determining the personal dose-equivalent, Hp(۱۰), in order to investigate whether the calibration curve in the Co-۶۰ gamma field can be utilized for assessing the dose-equivalent in the photon fields with different energies. To do this, first, the TLD dosimeters (an appropriate plastic badge including a TLD-۱۰۰ chip) are irradiated with a few Hp(۱۰) values using the Co-۶۰ source in the Karaj SSDL. The badges are placed on a water phantom (slab), one meter distant from the source. Then, MCNP۴C code is used to calculate the energy response at ۶۶۲ keV and ۱.۲۵ MeV energies. Next, these responses are validated with the experimental data. Finally, the calculation is carried out for several other energies in the range of ۲۰ keV to ۱.۲۵ MeV. Obtained results show that for the energies more than ۴۰۰ keV, The response of the dosimeter is independent of the photon energy, within ۱۰% uncertainty. On the other hand, for the energies smaller than ۴۰۰ keV, a significant dependence on the energy is observed; such that in ۴۰ keV the response is about ۲ times larger than that at ۱.۲۵ MeV. Consequently, a method to reduce this uncertainty is needed.

کلیدواژه ها:

Photon energy ، Response ، TLD ، dose-equivalent