Highly Sensitive Extrinsic X-Ray Polymer Optical Fiber Sensors Based on Fiber Tip Modification

An extrinsic X-ray fiber sensor with improved sensitivity is presented. The developed device is based on an inorganic scintillator (terbium-doped gadolinium oxysulfide) attached to a polymer fiber tip. Sensitivity improvement has been accomplished by modifying the fiber tip in two ways: by thermomechanical tapering and by chemical etching. Thus, the useful surface in contact with the scintillator increases, and so the fluorescence light gathering capability. All the fabricated devices have been tested under X-ray irradiation from a Linac at a dose rate of 300 monitor units/min, with a readout every 100 ms. The obtained results shown a signal improvement of up to 43 times when compared with previous reported proposals using inorganic scintillators and polymer fibers. Moreover, the recorded signal under the same measurement conditions can be further improved if the inorganic scintillator is used in powder format instead into an epoxy matrix.