Correction factors for Fricke dosimetry in high-energy electron beams

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Abstract
The paper presents Fricke-to-water dose conversion and wall correction factors for Fricke ferrous sulphate dosimetry in high-energy electron beams. The dose conversion factor has been calculated as the ratio of the mean dose in water to the mean dose in the Fricke solution with a water-walled vessel and the wall correction factor accounts for the change in the Fricke dose due to the presence of the non-water wall material. The EGS4 (electron gamma shower version 4) Monte Carlo code system has been employed in the work together with the application of a correlated sampling variance reduction technique. The results show that for a Fricke dosimeter of 1.534 cm diameter and 5.5 cm length the dose conversion factor is nearly constant at 1.004 (within 0.1%) for electron energies of 11-25 MeV if the dosimeter is placed at the depth of maximum dose but can vary by a few per cent if the dosimeter is placed on the descending portion of the depth-dose curve.