RF Modeling Plans for the European Spallation Source

The European Spallation Source (ESS) will be the world’s most powerful next generation neutron source. It consists of a linear accelerator, target, and instruments f or neutron experiments. The linac is designed to accelerate protons to a final energy of 2.5 GeV, with a design beam power of 5 MW, for collision with a target used to produce a high neutron flux. Several stages of RF acceleration are required, each using a different technology. The high beam current and power require a high degree of control of the accelerating RF, and the specification that no more than 1 W/m of losses will be experienced means that the excitation and decay of the higher order modes must be very well understood. Experiences at other high power machines also imply that an understanding of the generation and subsequent trajectories of any field-emitted electrons should be understood. Thermal detuning of the HOM couplers due to multipacting is a serious concern here. This paper will outline the RF modeling plans - including the construction of mathematical models, simulations of HOMs, and multipacting - during the current Accelerator Design Update phase, and will discuss several important issues for ESS.