TLD Responses Backed by Copper, Silver or Gold for 20-40 keV Monoenergetic Photons

Doses in TLDs backed by copper, silver or gold foils were measured using 20, 30 and 40 keV monoenergetic photons from synchrotron radiation. The TLDs used were LiF TLDs of 0.38 mm thickness and Li2B4O7:Cu of 90 μm thickness, and for the backing foils various thicknesses were used. The backscattering dose factor, which was defined as the ratio of the dose in the TLD with backing to that in free air, was found to become larger with decreasing TLD thickness and increasing foil thickness and photon energy. The dose eliminating the electrons from the foils was also measured by inserting a thin Teflon film between the TLDs and the foils. Compared with EGS4 Monte Carlo calculations, it was confirmed that the influence of the electrons became larger with decreasing TLD and foil thickness and increasing photon energy and atomic number of the foils. (author)