The influence of the magnetron frequency, the servo settings and the gantry angle on the flatness and the dose calibration of a linear accelerator

Abstract

For the Philips SL75/5, we have noticed that the performance of the beam (e.g. the hump) varies with the settings of the magnetron frequency and the gantry angle. This study investigated these changes and the optimum magnetron frequency setting was determined. The relation between the relative absorbed dose measured by the accelerator and the relative absorbed dose measured for different amounts of the hump in the centre of the beam was found. Results from a model and from measured values were compared. The beam was studied for different gantry angles and for different adjustments of the beam servo systems. The profiles obtained showed some variations, but were reduced when optimal ajustments of the servos were performed.