Spiral FFAG lattice design tools. Application to 6-D tracking in a proton-therapy class lattice

Methods have been developed, based on ray-tracing, for 3-D modelling of magnetic fields and particle motion in spiral scaling FFAG accelerators. They allow efficient simulation of particle motion in the presence of the strong field non-linearities found in FFAG magnets, and of overlapping fields in configurations of neighbouring magnets. This provides a useful tool for spiral FFAG lattice design and optimization, and for 6-D tracking studies. As illustration, the approach is applied to the design of a 180 MeV medical class proton FFAG now being studied under the RACCAM hadron-therapy project.