Kinetic Trapping Parameters in LiF:Mg,Cu,P via 'Prompt' and 'Residual' Isothermal Decay

The isothermal decay of peak 4 in Ben Gurion University-prepared LiF:Mg,Cu,P (SSD-NR) was monitored over an extended range of temperatures from 110°C to 192°C using both the prompt and residual techniques. Three batches of GR-200 material were also measured using either the prompt or the residual technique. The three batches of GR-200 material in both compacted and powdered form yielded essentially identical values of E and s; E = 1.23±0.03 eV and 3×1010 s-1 < s < 9x1011 s-1. The SSD-NR material is prepared in a unique manner which eliminates the high temperature structure at 270°C and results in a substantially narrower peak 4. For this material significantly different results are obtained; E = 1.47±0.03 eV and 2x1013 s-1 < s < 1014 s-1. These results for E and s, obtained by the isothermal decay technique, do not agree with previously reported values of E and s for peak 4 in LiF:Mg,Cu,P determined by 'peak shape' techniques which result in very high and unusual values; E>2 eV and s>1020 s-1. An identical anomaly exists for peak 5 in LiF:Mg,Ti. It appears likely that the trapping structures of peak 4 in LiF:Mg,Cu,P and peak 5 in LiF:Mg,Ti respond differently to isothermal heating than to linear heating.