Investigation of efficiency of thermoluminescence detectors for particle therapy beams

Dosimetric properties of thermoluminescence detectors produced at the Institute of Nuclear Physics were investigated with respect to their possible application in the dosimetry of proton radiotherapy beams. Relative TL efficiency, eta, was investigated with 5.3 MeV alpha particles for (i) CaF2:Tm (TLD-300 from Harshaw); (ii) LiF:Mg,Ti (MTS-N) sintered pellets with Ti content ranging from 4.3 to 130 ppm; (iii) LiF:Mg,Cu,P sintered pellets (MCP-N); (iv) thin layer DA-2 (CaSO4:Dy), and CaF2:Tm plated on 0.1 mm aluminium foil. The highest values of eta were found for LiF:Mg,Ti pellets with increased Ti content and TLD-300. The dose-response of all detectors was studied for 0.05, 0.5 and 5 Gy of Cs-137 gamma rays. LiF:Mg,Ti with increased Ti concentration and CaF,:Tm detectors were found to be linear in this dose range, while DA-2 and standard MTS-N detectors are supralinear and MCP-N is sublinear. MTS-N detectors were used to measure the dose-depth distribution in water for a 200 MeV proton beam, and showed good agreement with the readings of an ionisation chamber.