Energy control of the IMPELA series of industrial accelerators

Electron accelerator sources of radiation for industrial processes must maintain constant and reproducible irradiation parameters in order to provide satisfactory dose quality assurance. The advanced control system used in AECL's IMPELA series of accelerators ensures this by making it possible to decouple the primary accelerator variables, beam energy and beam current. Beam energy is made independent of current by controlling the field amplitude in the standing-wave structure during a relatively long pulse (50-500 μs) and an energy stability similar to that of dc machines is achieved. Experiments with the calibration linac facility at Chalk River show that the beam energy can be held constant to within ±2% on an absolute basis. This eliminates the requirement for the complex beam analysis after acceleration used on short-pulse linacs. Methods for the measurement of energy at the users site and at the calibration facility are described. (orig.)