Assessment of calibration coefficient ND, W in terms of absorbed dose-to-water of some ionization chambers
1 Secondary Standard Dosimetry Laboratory, Health Physics and Radioactive Waste Management Unit, Institute of Nuclear Science and Technology, Atomic Energy Research Establishment.
2 Planning and Development Division, Bangladesh Atomic Energy Commission, Dhaka.
Research Article
Global Journal of Engineering and Technology Advances, 2020, 05(01), 025-031.
Article DOI: 10.30574/gjeta.2020.5.1.0066
Publication history:
Received on 02 September 2020; revised on 07 October 2020; accepted on 10 October 2020
Abstract:
The absorbed dose-to-water calibration coefficients ND,W of some ionization chambers were determined in terms of the secondary standard chambers in 60Co gamma-ray beam based on the TRS-398 protocol. The reference absorbed dose-to-water Dw were measured using secondary standard ionization chambers of model NE 2781#0537 (0.60 cm3 volume) and NE 2771#1205 (0.69 cm3 volume) which are traceable to the dosimetry laboratory of the International Atomic Energy Agency (IAEA). This study mainly focuses on the comparative assessment of the determined ND,W coefficients of twenty cylindrical ionization chambers from various user groups. The determined ND,W coefficients were compared with the manufacturer provided ND,W coefficients. The observed percentage of deviation between the measured and the manufacturer’s ND,W coefficients among all the chambers were found to be in the range of 0.019% and -2.263% as the least and highest, respectively. The observed percentage of deviations for studied chambers were found within the IAEA’s acceptance limit of 1.5% with an exception for three chambers. This observed discrepancy with the IAEA’s acceptance limit for the three chambers out of the twenty chambers, indicates the calibration necessity before using chambers in routine reference dosimetry. In ND,W measurement, the uncertainty Uc is reported with the coverage factor k=1 that providing a level of confidence of approximately 68%.
Keywords:
Calibration; Absorbed dose-to-water; Dosimetry; Radiotherapy; Karma; Ionization chamber.
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