The beam loading effect in the multicavity linear accelerator and the requirements for the RF control system

This work has been done in the frame of ESS collaboration. The high intensity proton beam with 60 mA average current is supposed to be accelerated in the ESS linac up to 1.3 GeV. The ratio between the beam power and the losses power is changed along the accelerator from 0.6 to 0.7. With such a strong beam loading effect, the amplitude and phase RF field instabilities cause the growth of the effective longitudinal emittance at the exit of the multicavity linear accelerator. It gives rise to the difficulties with the injection of the beam in the ring. We define the requirements to the RF control system, taking this effect into account