engleski

Dose mapping of the panoramic 60Co gamma-ray source

The panoramic 60Co source of the Ruđer Bošković Institute (RBI) is the only irradiation facility in Croatia suitable for a variety of applications: from medium range doses used in radiobiology and accident dosimetry to high doses used in radiation research and radiation processing. The operator of the facility, Radiation Chemistry and Dosimetry Laboratory enables an open access to a number of users working in diverse fields, from physics to biology, from arts to engineering, both from within and beyond the Institute. This policy enabled Croatian scientists to accomplish some important results using radiation in various fields in the past. The aim of the present work is to describe the irradiation facility, on account of its dosimetric calibration and details of the radiation field within the irradiation chamber. Dose mapping was performed primarily with an ethanol-chlorobenzene (ECB) dosimetry system containing five characteristic concentrations (4, 10, 20, 25 and 40 vol. % of chlorobenzene in 96 vol. % ethanol) [1, 2]. Several different dosimetry methods, including ionization chamber measurements, were used for precise dosimetric calibration of the source, which makes possible the calculation of dose received by samples of various compositions, sizes and shapes [3, 4]. All doses were expressed as “absorbed dose to water”, obtained from doses absorbed in ECB solutions multiplied with appropriate ratios of mass energy absorption coefficients for water and respective ECB formulations (ISO/ASTM, 2017). In this work we are presenting the results of the dosimetric calibration and examining the nature of dose distribution curves of the RBI cylindrical gamma ray panoramic source geometry. Also, we are presenting the results of the “transit dose” determinations (the dose absorbed during the movement of the source to and from its irradiation position). This dose has to be taken into consideration at doses lower than 10 Gy, i.e. mostly for experiments in radiobiology. References [1] D. Ražem et al., Consistency of ethanol- chlorobenzene dosimetry. Proceedings of IAEA Symposium on High-Dose Dosimetry, 1985, Vienna, 143-156. [2] S. Miljanić et al., Appl. Radiat. Isot., 1993, 44, 711-718. [3] Zs. Horváth et al., Radiochim. Acta 1970, 13, 150-152. [4] I. Dvornik, The ethanol-chlorobenzene dosimeter. In Manual on Radiation Dosimetry, (Eds. N.W. Holm and R.J. Berry) Marcel Dekker, New York, 1970, p.345.

gamma-irradiation ; dose mapping ; panoramic source

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