Graphite ionization chamber as an ionometric standard of absorbed dose to water for Co-60 radiation

In the paper GUM-Dw3 graphite-walled cylindrical cavity ionization chamber (of design and volume typical for the chambers for radiation therapy dosimetry) was presented as a realization of an ionometric standard for absorbed dose to water. A state-of-the-art uncertainty budget and results of comparison to GUMs standards has been presented. Good agreement of absorbed dose to water with reference standard, with relative deviation of 0.28%, and standard uncertainty (k=2) of 0.48% indicates good quality of the GUM-Dw3 as a primary standard. This paper describes the step-by-step procedure to calculate a perturbation factor, that is a crucial issue for ionometric measurement of absorbed dose to water. Capabilities of FLUKA code for this factor determination have been also investigated.