Experimental measurements confirm decreased supralinearity in the thermoluminescence of beta/gamma irradiated LiF:Mg,Ti (TLD-100) following 3.6 eV and 5 eV optical excitation

Abstract

Photon excitation at selected energies following beta/gamma irradiation is found to significantly reduce the supralinearity of the thermoluminescence dose response of composite peak 5 in LiF:Mg,Ti (TLD-100). Following a dose of 100 Gy, photon excitation at an energy of 5 eV and fluence of 1.3 × 1018 ph cm−2 reduces the normalized TL efficiency from 2.8 to 1.9 and at 400 Gy from 3.5 to 2.7. Excitation by photons of energy 3.65 eV (1019 ph cm−2) reduces the normalized efficiency of glow peak 5a (a low temperature satellite of peak 5) at 100 Gy from 2.9 to a value of 0.95 thereby resulting in a linear dose response. The high values of dose of 100 Gy and 400 Gy well beyond the normal dose range of clinical radiation therapy were chosen for demonstrative purposes in order to evaluate the likelihood of success of the proposed technique. Additional experiments are underway to determine the photon levels of fluence, which will result in a linear dose response for both glow peaks 5, and 5a in the range of doses 1-30 Gy of interest to radiotherapy and intraoperative electron therapy.