The Monte Carlo code MCNP-4C2 is used to design a new personal thermoluminescence dosemeter that assesses both Hp (10) and Hp (0.07) in mixed photon/electron fields. The new dosemeter utilizes two 7LiF:Mg,Cu,P elements contained within a Harshaw TLD-700H card, itself inside a polypropylene holder with walls 2 mm thick. Several potential designs of holder are considered; the best incorporates a polytetrafluoroethylene cylinder of diameter 18 mm and thickness 4.3 mm that acts as a filter to provide the correct electron cut-off and an acceptably flat Hp (10) relative response to photons, with an open hole in front of the Hp (0.07) element. Response characteristics for both detectors in this final design are presented for irradiation from a variety of angles of interest, with source energies between 16 and 6174 keV used. Comparison is made between modelled and measured data at normal incidence; the relative responses generally agree well. A new estimate for the relative light conversion efficiency relevant to the 7LiF:Mg,Cu,P is also derived and presented.
- Monte Carlo modelling
- Personal dosemeter