A RADIATION DETECTOR CONSTRUCTED WITH GSO SCINTILLATOR AND PLASTIC OPTICAL FIBER COMBINATION FOR REMOTE DOSIMETRY OF GAMMA-RAY FIELDS

摘要

A fiber-optic dosimeter model is constructed with a small piece of Gd_2SiO_5 (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 ~(60)Co 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 ~(60)Co irradiation chamber with an activity of ～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 ~(60)Co 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 ~(60)Co 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.