Characteristics of a Ce-Doped silica fiber irradiated by 74 MeV protons

A Ce-doped silica fiber, part of the UniBEaM25 charged-particle beam profiler system from D-Pace, was tested for use in proton therapy dosimetry with a 74 MeV proton beam at the Proton Therapy Facility at TRIUMF, Canada. Repeatability, dose response, dose rate response, and measurements of the horizontal, vertical and axial beam profiles for a raw Bragg peak as well as a spread-out Bragg peak were investigated. For the given irradiation conditions, the fiber's light output was reproducible with percent standard deviation of 1.15%, and has a linear response to irradiated dose length, accumulated dose, and total dose rate with R2 > 0.99 for each. A significant quenching of the signal at high energy deposition for protons was observed, with a peak-to-plateau value of 2.79 and a Birk's constant of kB  = 2.34 × 10−2cm/MeV.