Performance of a 6 MeV Varian linear accelerator.

Abstract The performance of a Varian 6 MeV Linear Accelerator in which the electron beam is bent through 90 deg. is reported. Initially the machine was unacceptable for treatment purposes mainly because of variations in the asymmetry of the X-ray beam. The steps taken to correct the causes of asymmetry are described together with the improved behaviour of the machine. It is emphasised that care must be taken in the initial positioning of the beam flattener, in adjusting the symmetry servo amplifier and in the daily checking of magnetron frequency and beam energy. Measured central axis depth dose data are available for a range of square field sizes from 4 × 4 cm to 25 × 25 cm to a depth of 30 cm for 100 cm S.S.D. and similar data for 92·5 and 85 cm S.S.D. are available from the authors.