Proton irradiation of (LiF)-Li-7 : Mg,Ti thermoluminescent detectors: influence of dopant concentration on dose response and let dependence of TL efficiency

Loncol, Th. Denis, J.M. Vynckier, Stefaan [UCL] Scalliet, Pierre [UCL] Bilski, P. Budzanowski, M. Waligorski, M.P.R. Olko, P. et al.[show all]

Variation of Ti and Mg concentration is known to modify substantially the dosimetric characteristics of the standard LiF:Mg,Ti detector commonly used in radiotherapy. Preliminary studies conducted by the Institute of Nuclear Physics at Krakow suggested that the Ti concentration could be optimised with respect to low supralinearity and high TL efficiency in heavy particle beams. These results led to further investigation of new TL detectors appropriate to proton therapy. In particular, the influence of both Mg and Ti dopant concentrations on TL response in proton beams was studied.(LiF)-Li-7:Mg,Ti pellets (diameter 4.5 mm, thickness 0.5 mm) doped with 30 different combinations of Ti and Mg (five Ti concentrations: 4, 13, 39, 130, 260 ppm; six Mg concentrations: 30, 60, 120, 240, 480, 960 ppm) were irradiated in a 65 MeV proton beam at two different positions in a Perspex phantom corresponding to different depths in the Bragg curve. From the analysis of dose response and TL efficiency and its dependence on LET, recommendations on optimal dopant concentration are drawn for the clinical use of the dosemeter in proton therapy.