Research and analysis

The Health Protection Agency TLD: photon cross-section data

This report (HPA-RPD-049) concerns photon cross section data in absorbed dose calculations for the HPA thermoluminescent dosimeter.

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Air kerma data and the relative response of the new HPA thermoluminescent dosimeter were calculated for Narrow Series X-ray distribution and caesium-137 photon sources using the general purpose Monte Carlo code MCNP5. The results were compared to those obtained using its predecessor, MCNP4c2.

It was found that the results differ at low energies by up to ~10 %. This disparity was mainly ascribed to differences in the default photon interaction data used by the two codes, and derived ultimately from the influence on absorbed dose of the recent updates to the photoelectric effect cross sections.