Effects of cooling and heating rate on trapping parameters in LiF:Mg, Ti crystals

The effects of the cooling rate alpha and heating rate beta on trapping parameters and thermoluminescent (TL) glow peak intensities in LiF:Mg, Ti(TLD-100) crystals have been studied by glow curve fitting from room temperature to 500 K. It is found that under the investigated circumstances (1 K min -1 < alpha < 5000 K min -1 , 0.12 K s -1 < beta <20 K s -1 , dose approximately= 40 mGy) all measured glow curves can be fitted very well according to the Randall-Wilkins model (1.6%>FOM>0.2%). Glow peak intensities (peak area) for peaks 2,3,4 and 5 increase with both increasing cooling rate and heating rate in accordance with earlier investigations. However, the activation energies for most peaks vary strikingly with both cooling rate and heating rate: for peak 2 from 1.12 to 1.38 eV, for peak 3 from 1.06 to 1.43 eV, for peak 4 from 1.55 to 1.87 eV and for peak 5 from 1.73 to 2.08 eV. A qualitative explanation has been given in terms of clustering and precipitation of the defects responsible for TL during the annealing and readout stage.