X-ray induced Sm3+ to Sm2+ conversion in fluorophosphate and fluoroaluminate glasses for the monitoring of high-doses in microbeam radiation therapy

Fluorophosphate and fluoroalutninate glasses doped with trivalent samarium were evaluated as sensors of x-ray radiation for microbeam radiation therapy at the Canadian Light Source using the conversion of trivalent Sm3+ to the divalent form Sm2+. Both types of glasses show similar conversion rates and may be used as a linear sensor up to similar to 150 Gy and as a nonlinear sensor up to similar to 2400 Gy, where saturation is reached. Experiments with a multi-slit collimator show high spatial resolution of the conversion pattern; the pattern was acquired by a confocal fluorescence microscopy technique. The effects of previous x-ray exposure may be erased by annealing at temperatures exceeding the glass transition temperature T-g while annealing at T-A < T-g enhances the Sm conversion. This enhancement is explained by a thermally stimulated relaxation of host glass ionic matrix surrounding x-ray induced Sm2+ ions. In addition, some of the Sm3+-doped glasses were codoped with Eu2+-ions but the results show that there is no marked improvement in the conversion efficiency by the introduction of Eu2+. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754564]