DEPENDENCE OF LIF-MG,CU,P (MCP-N) GLOW CURVE STRUCTURE ON DOPANT COMPOSITION AND THERMAL-TREATMENT

In a systematic investigation of the effect of dopant composition on d osimetric characteristics of thermoluminescent LiF:Mg,Cu,P phosphor, 1 30 samples were prepared with different concentrations of all activato rs over the following ranges: Mg (0-1.0 mol%), Cu (0-0.5 mol%) and P ( 0-5.0 mol%). From each material a group of sintered detectors was prod uced. Parameters describing the shape of the glow curve were analysed after standard annealing at 240 degrees C and after annealing at tempe ratures up to 400 degrees C. It appears that the amplitude of the main dosimetric peak 4 depends on the concentration of Cu and Mg, showing a distinct maximum for certain concentrations of these dopants. Intens ities of high temperature peaks tend to rise with increasing Mg and de creasing Cu concentration. The dependence of the amplitude of peak 4 o n P concentration is a step function, rising by an order of magnitude as the amount of P exceeds a threshold value of 0.15 mol%. It appears that copper does not participate in the formation of traps nor of lumi nescent centres and plays an indirect role, that of inhibiting the gro wth of high-temperature peaks. Increase of annealing temperatures up t o 270 degrees C results in a decrease of the signal from high temperat ure peaks and in an increase of the main peak intensity (for most comb inations of dopant composition). At annealing temperatures above 270 d egrees C intensities of all peaks decrease. This thermal susceptibilit y of LiF:Mg,Cu,P appears to be associated with the instability of Mg-r elated defects.