Initial studies of a 2-colour FEL amplifier using one monoenergetic electron
beam are presented. The interaction is modelled using the unaveraged, broadband
FEL code Puffin. A series of undulator modules are tuned to generate two
resonant frequencies along the FEL interaction and a self-consistent 2-colour
FEL interaction at widely spaced non-harmonic wavelengths at 1nm and 2.4nm is
demonstrated.Comment: Submitted to The 35th International Free-Electron Laser Conference,
Manhattan, New York (2013