Beam dynamics of the ESS linac

The ESS linac will deliver an unprecedented 5 MW of average beam power when completed. Beyond the 90 MeV normal conducting front-end, the acceleration is performed using superconducting structures up to the design energy of 2 GeV. As the ESS will send the beam to a fixed tungsten target, the emittance is not as important a factor as in injectors. However, the losses have to be studied in detail, including not only the average operational loss required to be of less than 1 W/m, but also the accidental losses, losses due to failure and other potentially damaging losses. The commissioning of the ion source and LEBT starts this year and will continue with the RFQ next year. In this contribution we will discuss the beam dynamics aspects and challenges of the ESS linac.