REDUCING ENERGY SPREAD OF THE BEAM BY NON-ISOCHRONOUS RECIRCULATION AT THE S-DALINAC

The Superconducting Linear Accelerator S-DALINAC at the University of Darmstadt/ Germany is a recirculating linac with two recirculations. Currently acceleration in the linac is done on crest of the acceleration field using the maximum of the field in every turn. The recirculation of the beam is done isochronous without any longitudinal dispersion. In this recirculation scheme the energy spread of the resulting beam is determined by the stability of the used RF system. In this work we will present a new nonisochronous recirculation scheme, which uses longitudinal dispersion in the recirculations and an acceleration on edge of the accelerating field as it is done in microtrons. We will present beam dynamic calculations which show the usability of this system even in a linac with only two recirculations and first measurements of longitudinal dispersion using rf monitors.