A Radiation Detector Constructed with GSO Scintillator and Plastic Optical Fiber Combination for Remote Dosimetry of Gamma-Ray Fields

A fiber-optic dosimeter model is constructed with a small piece of Gd₂SiO₅ (GSO) scintillator optically attached to a low attenuating plastic optical fiber. The lights generated in the scintillator are transmitted through the fiber and read by a current-type photomultiplier tube (PMT). The dosimeter model was tested with two ⁶⁰Co standard sources of 1.85 and 37 MBq by measuring the PMT current as a function of the source-to-detector distance. It was then tested in a ⁶⁰Co irradiation chamber with an activity of [approximately]244.2 TBq. MCNPX simulations were performed for the source and dosimeter arrangements to calculate the deposited energy in the GSO scintillator. When tested with standard ⁶⁰Co sources of 1.85 and 37 MBq, the dosimeter model did not produce satisfactory results. However, better results were obtained with the higher-activity source. In the test in a ⁶⁰Co irradiation chamber of 244.2 TBq, the measured data well coincide with the MCNPX simulation results. In a direct comparison with a Farmer-type ion chamber, it is found the dosimeter readings can be simply converted to the air kerma doses by proper calibration.