Fiber optic microprobes with rare-earth-based phosphor tips for proton beam characterization

摘要

We investigated the feasibility of using fiber optics probes with rare-earth-based phosphor tips for proton beam radiation dosimetry. We designed and fabricated a fiber probe with submillimeter resolution based on TbF_3 phosphors and evaluated its performance for measurement of proton beams including profiles and range. The fiber optic probe, embedded in tissue-mimicking plastics, was irradiated with a clinical proton beam and the luminescence spectroscopy was performed by a CCD-coupled spectrograph to analyze the emission spectra of the fiber tip. By using a linear fitting algorithm we extracted the contribution of the ionoluminescence signal to obtain the percentage depth dose in phantoms and compared that with measurements performed with a standard ion chamber. We observed a quenching effect in the spread out Bragg peak region, manifested as an under-responding of the signal due to the high linear energy transfer of the beam. However, the beam profiles measurements were not affected by the quenching effect indicating that the fiber probes can be used for high-resolution measurements of proton beams profile.