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

摘要

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 (60)Co 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.