Loss monitoring for undulator protection at SwissFEL

At the x-ray free-electron laser SwissFEL, at the Paul Scherrer Institute, Switzerland, beam loss monitors are used to determine loss positions along the linear accelerator and protect critical elements such as the undulator magnets from excess radiation. These monitors are integrated into the machine protection system (MPS) allowing beam losses to be limited by dynamically reducing the repetition rate. This paper focuses on the types of loss monitors installed at SwissFEL and their function in protecting the machine.