[Constancy check of the radiation output of Linac: comparison with diodes and ionization chamber]

For routine QA measurements of the radiation output of a linear accelerator, an ionization chamber is usually used, the type of which may depend on the radiation quality. In this study, a comparison of the standard ionization chamber and the central diodes of an array, was performed both used simultaneously for the constancy check of the radiation output. It was investigated to which degree the two detectors deviate from each other over a long period of time for different radiation qualities. The aim of the study was to show whether the radiation output can be checked using the diode array, which is usually used for measuring beam profiles, by averaging the values of the central diodes within a reasonable accuracy. The results showed a maximum deviation of the two detectors of 0.9-2.2%, whereas the mean deviation is 0.4-0.8%, both depending on the radiation quality.