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Chemical Dosimetry

Chemical dosimeters are best qualified for the measurement of high, kGy-range, doses, utilising the chemical reactions induced by ionising radiation within the medium. The radiolysis of water develops radicals which irreversibly oxidate the metal ions of the solution. FRICKE-Dosimetry uses ferrous sulphate where Fe2+ is translated to Fe3+. The mechanism of this dosimeter lies in the proportionality between the applied energy dose and the concentration of produced Fe3+.

Frickeschema
Extinction of irradiated Fe-solution
compared with the original solution


To determine the dose, the concentration of Fe3+ must be quantified. For this, the optical density E (extinction) of the original and the irradiated dosimeter solutions are measured with a spectral photometer and compared. Iron(III)ions show an absorption maximum at 304 nm. The absolute value of the extinction around this wavelength is directly proportional to the absorbed dose.

Dose characteristic of the Fe-Cu-Dosimeters: Measured
dose DFe-Cu against applied dose DQ


FRICKE-Dosimetry is applicable in the dose range between 5 Gy and 0.4 kGy. For higher doses, the system goes into saturation. With a modification of the solution it is possible to shift this measuring range to higher doses. I.e., the raise of the Fe2+-concentration effects that the saturation starts not until 1.5 kGy. The addition of Cu2+ (ferrous sulphate-copper sulphate-dosimeter) enables the measurement of doses of at least 25 kGy.

For questions and remarks concerning this web page please send email to: PD Dr. J. Henniger
Last Update: 04. 12. 2014
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