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Evolution of the CaF 2 :Tm (TLD-300) glow curve as an indicator of beam quality for low-energy photon beams

2015; IOP Publishing; Volume: 60; Issue: 6 Linguagem: Inglês

10.1088/0031-9155/60/6/2135

1361-6560

Iván Domingo Muñoz, O. Ávila, I. Gamboa‐deBuen, M.E. Brandan,

Radiation Therapy and Dosimetry

We study the high- to low- temperature signal ratio (HLTR) of the CaF2:Tm glow curve as a function of beam quality for low-energy photon beams with effective energy between 15.2 and 33.6 keV, generated with W, Mo and Rh anodes. CaF2:Tm dosemeters (TLD-300) were exposed to x-rays and 60Co gamma-rays. Glow curves were deconvoluted into 7 peaks, using computerized glow curve deconvolution and HLTR was evaluated. Air kerma and dose in water were between 2.1–15.0 mGy and 49.8–373.8 mGy, respectively. All peaks in the glow curve showed a linear response with respect to air kerma and dose in water. HLTR values decreased monotonically between 1.029 ± 0.010 (at 15.2 keV) and 0.821 ± 0.011 (33.6 keV), and no effects due to the use of different anode/filter combinations were observed. The results indicate a relatively high value of HLTR (about 1 for 17 keV effective energy, or 3 keV μm−1 track-average LET) and a measurable dependence on the photon beam quality. Comparison of these photon data with HLTR for ions shows good quantitative agreement. The reported evolution of the CaF2:Tm glow curve could facilitate the estimation of the effective energy of unknown photon fields by this technique.