Application of radiation physics in the design of the Harshaw 8828 beta–gamma TLD badge

A thermoluminescent dosimeter (TLD) badge has been developed to measure beta and gamma doses for routine personal dosimetry. The badge uses a card with four elements of LiF:Mg,Ti enriched in 7Li and sandwiched between layers of Teflon™. The Element 1 filter is 1000mgcm-2 of low-Z material, the Element 2 filter is 464mgcm-2 of tin plus 536mgcm-2 of low-Z material, the Element 3 filter is a 5–7mgcm-2 Mylar window, and the Element 4 filter is 64mgcm-2 of low-Z material. The filters for Elements 2 and 4 were optimized by testing and by application of radiation physics principles and calculation. Elements 1 and 2 are used to measure the response to photons, and from these results, HpHp(10), HpHp(0.07) for photons, and the photon contribution to the signals for Elements 3 and 4 are obtained. The photon contribution to the signals from Elements 3 and 4 is subtracted from their total signals to obtain two signals due to betas. These are used to derive a corrected value for HpHp(0.07) for betas. The badge has been in use since early 1999, and provides accurate results in a nuclear power station environment.