Estimation of electron dose delivered by a 0.4 MeV accelerator from bremsstrahlung dose measurements

Determination of a 0.4 MeV electron dose from a bremsstrahlung dose measurement using a converter-detector system is considered. The detector used is a Fricke dosimeter, and the converters are aluminium, copper and lead foils. Optimal converter thickness is ascertained experimentally for each material, namely: Al, 0.13 g/cm2; Cu, 0.06 g/cm2; and Pb, 0.045 g/cm2. The corresponding peak bremsstrahlung doses at 20 Mrad electron dose in water are 376, 460 and 940 rad, respectively. A relation is given enabling prediction of optimal converter thickness and peak bremsstrahlung dose for converter materials within a Z-range of 13 to 82. A linear relation is found between bremsstrahlung dose and electron dose ranging from 2 to 20 Mrad. Finally the effect of converter area on detector response is studied. (author)