Monte Carlo Modelling Of A Tld Device Containing (Lif)-Li-7 : Mg,Cu,P Detectors

The Monte Carlo code MCNP-4C2 is used to design a new personal thermoluminescence dosemeter that assesses both H-p(10) and H-p(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 min thick. Several potential designs of holder are considered; the best incorporates a polytetrafluoroethylene cylinder of diameter 18 min and thickness 4.3 min 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 H-p(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 6174keV 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. (C) 2008 Health Protection Agency. Published by Elsevier Ltd. All rights reserved.