Build-up curves of scanned high energy electron beams from the Sagittaire linear accelerator

A study of the build-up curves using an extrapolation chamber for 7, 10, 13, 16, and 19 MeV electron beams, from a Sagittaire linear accelerator, is presented. The effect of the ionization chamber bias polarity, field size, collimation and surface obliquity on the shape of the relative ionization curve was investigated. No clinically significant change is observed except the displacement of the maximum ionization point was observed for the oblique incidence of the beam.