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| Study on the calibration method of absorbed dose to water using pinpoint ionization chamber |
| HE Zhijian, YUAN Jilong, XUE Xian, CHENG Jinsheng |
| Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088 China |
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Abstract Objective To establish a calibration method of the absorbed dose to water using pinpoint ionization chamber at the radiation quality of 60CO gamma rays. Methods Reference dosimeter (FC65-G Farmer ionization chamber with DOSE 1 electrometer) was calibrated by the China Institute of Metrology for obtaining the absorbed dose calibration factor to water. 60Co gamma rays and the IAEA TRS-398 measuring procedure were used to measure the absorbed dose at depth of 10 cm water with the reference dosimeter. Alternative method, the water absorbed dose measurement and calibration of two pinpoint ionization chamber dosimeters were carried out. Replacing the 60Co gamma radiation field, the reference dosimeter and two pinpoint ionization chamber dosimeters were used to verify the dose. Results The measured results of absorbed dose to water at depth of 10 cm water at reference conditions were 0.249 9 Gy for reference dosimeter, 0.248 0 Gy and 0.250 0 Gy for two pinpoint ionization chambers,respectively. The relative deviations of the measurement were within ±0.8% between the reference dosimeter and two pinpoint ionization chamber dosimeters. The measurement uncertainty of the pinpoint ionization chamber was 2.8% (k=2). Conclusion The pinpoint ionization chamber can be used to measure the absorbed dose to water of small field.
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Received: 04 September 2018
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