TL Glow Curve

The pattern of TL glow curves, in both shape and intensity, vary in a characteristic manner, reflecting the higher order structure of the polymer molecules. The TL peak in a glow curve can be attributed to the molecular relaxation of each sample. 

---

In its basic design, the equipment is similar to a 2-D TL glow-curve system as described previously, but with the addition of a modified Twyman-Green, Michelson type, interferometer between the oven and the photomultiplier. As the sample is heated, the TL signal is recorded while the movable mirror of the interferometer is scanning a given optical path difference in a preset number of steps. The interference pattern corresponding to each one-way scan... 

Figure 9.33. TL glow curve obtained on a substance with three different trap depths and populations (90).

A Y source from °Co was used for irradiation of the samples. TL glow curves were recorded with the usual set up of a Nucleonix TL-1009, consisting of a small metal plate heated directly using a temperature programmer, photomultiplier tube (931B), dc amplifier, and millivolt recorder. A 5 mg amount of phosphor in the form of fine powder was heated each time at a rate of 5°C/s. 

The TL glow curves of the LiNaS04 Cu sample exposed to different doses in the range from 0.1 to 16 Gy of Co gamma-rays are shown in Figure 7.6. The samples were exposed to different doses, but there is no change in the glow curve structure or even in the peak position. Reusability and thermal stability of this sample was also studied. 

TL glow curves of LiNaS04 Cu,Mg powder exposed to different amounts of ganuna doses are shown in Figure 7.8. The intensity of the TL peak increases with the increase of the concentration of Mg " and becomes optimum for 0.1 mol% of concentration of Mg. Efforts were made to increase the sensitivity by co-doping with Mg +, which provides charge compensation at Na site and higher concentration of dispersed Cu+ at the Li+ site may be achieved. 

FIGURE 7.6 TL glow curves of crystalline LiNaS04 Cu Q2m% for different doses (heating rate=5°C/s). 

The intensity and structure of the TL glow curve did not change after several cycles of exposures and readout. The present study shows a remarkable result obtained on Mg co-doped LiNaS04 Cu material. This sample is found to provide a highly sensitive material for gamma-rays. This result demonstrates the role of Cu and Mg inside the host of LiNaS04. The density of the electron traps induced by Mg is much more than that of Cu. It is seen that the TL intensity of LiNaS04 Cu,Mg for Mg=0.1 mol% and Cu=0.2 mol% is optimized. 

The determination of trapping parameters from the TL glow curves is an active area of interest and various techniques have been developed for the determination of trapping parameters, namely activation energy (E), order of kinetics (b), and frequency factor (s) (Sharma 2005). Analysis of... 

Figure 7.19 shows the characteristic TL glow curves of LiNaF2 Cu,P powder exposed to 16 Gy of °Co gamma-rays together with the glow curve of standard TLD CaS04 Dy commercially available... 

FIGURE 7.19 TL glow curves of (a) LiNaF2 Cu,Po.2moi% nd (b) TLD CaS04 Dy exposed to 16Gy of gamma-rays of °Co. 

No degradation in the phosphor quality was observed due to storage in laboratory conditions. The total fading of the 143°C peak over this period of storage was around 2.5%. The intensity and structure of the TL glow curve did not change after several cycles of exposures and readout. 

---