Supralinear response of LiF:Mg,Ti (TLD-100) after exposure to 100 keV average energy X-rays

The response of LiF:Mg,Ti (TLD-100) induced by 100 keV average energy X-rays has been investigated for air kerma values between 10 mGy and 1000 Gy. Measurements were performed in air, using the NIST M200 beam (200 kV operating voltage). The air kerma at the dosimeter surface was measured with a free-air chamber, with combined uncertainty between 0.06% and 0.08% in air kerma rate. A careful protocol was followed to deconvolute glow curves into individual peaks. Results indicate stronger supralinearity (maxima higher than 10) for high-temperature (6a–9) than for low-temperature (4–5) peaks. Comparing with the response induced by 60Co gamma rays, the region where the TL response is linear extends to higher doses for 100 keV X-rays than for gammas. The maximum dose response functions are much smaller for 100 keV X-rays than for 60Co (for instance, 40 vs. 232 for peak 8). The dose response function measured in this work was used as a reference radiation for Modified Track Structure Theory, MTST, calculations aimed at describing relative TL efficiency for a variety of intermediate energy ions. The ions secondary electron spectra are better matched to this reference radiation than to 8 keV or 1.25 MeV, previously used as references. The use of 100 keV X-rays has not improved the agreement between calculations and the ion-efficiency data.