  The performance of the energy degrader in terms of beam properties directly
impacts the design and cost of cyclotron-based proton therapy centers. The aim
of this study is to evaluate the performances of different existing and novel
degrader materials. The quantitative estimate is based on detailed GEANT4
simulations that analyze the beam-matter interaction and provide a
determination of the beam emittance increase and transmission. Comparisons
between existing (aluminum, graphite, beryllium) and novel (boron carbide and
diamond) degrader materials are provided and evaluated against semi-analytical
models of multiple Coulomb scattering. The results showing a potential in
emittance reduction for novel materials are presented and discussed in detail.
