Effect of dopants on TL characteristics of LiF:Mg,Cu,P detectors
Abstract LiF:Mg,Cu,P detectors produced at the Institute of Nuclear Physics in Krakow have shown very good dosimetric characteristics. Understanding of the effect of the concentration and type of dopants is important in the characterization of TL materials. The aim of work was to investigate the influence of the type and concentration of the dopants on the photon energy response of these detectors by irradiations “in air” and on the ISO water phantom in the range of mean photon energies between 33 and 164 keV. The influence of dopants on the glow curves, sensitivity and reproducibility was also examined. Results showed that measured energy dependence values are lower compared to the theoretical values both “in air” and on phantom. The type and concentration of the dopants influence the shape of the glow curves and sensitivity while for energy dependence is more important the presence of certain activators, namely copper.
Influence of concentration of magnesium on the dose response and LET-dependence of TL efficiency in LiF:Mg,Cu,P (MCP-N) detectors
Abstract The highly-sensitive LiF:Mg,Cu,P phosphor, unlike the supralinear LiF:Mg,Ti, exhibits a linear–sublinear dose response after high doses of photon radiation. Also, LiF:Mg,Cu,P shows a much stronger decrease of relative efficiency with increasing ionisation density, especially for heavy charged-particle irradiation. The magnesium dopant most likely governs the trap structure in both phosphors. Dose-response and LET-dependence were therefore studied in LiF:Mg,Cu,P with different concentrations of Mg. Samples of LiF:Mg,Cu,P detectors with eight different values of magnesium concentration C Mg ranging from 0.05 to 0.8 mol%, were produced in which the concentration of P and Cu was fixed at 1.25 and 0.05 mol%, respectively. Detectors were irradiated with 5.3 MeV alpha-particles and 137 Cs gamma-rays and relative efficiency evaluated for all groups of samples. Relative efficiency η αγ appears to decrease with increasing magnesium content: from η αγ ≈0.13 at C Mg =0.05 mol% to η αγ ≈0.06 at C Mg =0.20 mol%, and is less dependent on C Mg at higher concentration of Mg. In the study of LiF:Mg,Cu,P response after 137 Cs photon doses (1–1000 Gy) in samples with C Mg =0.1 and 0.2 mol%, typical sublinear response was observed, the sublinearity of 0.1 mol% detectors commencing at higher doses. In contrast, in the least Mg-doped sample (0.05 mol%) strong supralinearity in the dose response was found, resulting from the growth of a new peak at about 200°C which at 1000 Gy and at 500 Gy dominates the TL glow-curve over the usual main peak at 240°C.
The light conversion efficiency of TLD-700 for alpha particles relative to cobalt-60 gamma radiation.
7LiF:Mg, Ti in the form of hot pressed chips were used in experiments on the light conversion efficiency (n) of TLD-700 for alpha -particles relative to 60Co gamma -rays. Glow curves are shown. Peak heights and glow curve areas were recorded. eta was found in general to increase with alpha -particle energy.