Detecting electron beam energy shifts with a commercially available energymonitor

Routine electron beam quality assurance requires an accurate, yet practical , method of energy characterization. Subtle shifts in beam energy may be pr oduced by the linac bending magnet assembly, and the sensitivity of a comme rcially available electron beam energy-monitoring device for monitoring the se small energy drifts has been evaluated. The device shows an 11% change i n signal for a 2 mm change in the I-50 energy parameter for low energy elec tron beams (in the vicinity of 6 MeV) and a 2.5% change in signal for a 2 m m change in the I-50 energy parameter for high energy electron beams (in th e vicinity of 22 MeV). Thus the device is capable of detecting small energy shifts resulting from bending magnet drift for all clinically relevant ele ctron beams. (C) 2000 American Association of Physicists in Medicine. [S009 4-2405(00)01807-1].