Two harmonic undulators and harmonic generation in high gain free electron lasers

摘要

We consider an undulator scheme to enhance harmonic generation in high gain free electron lasers. The configuration we consider consists of an undulator providing an on axis field oscillating in both transverse directions, with relatively integer multiple spatial periods. We discuss the spectral properties of the radiation emitted by relativistic electrons crossing this undulator and derive the equations describing the free electron laser evolution. We show that a device, exploiting such an undulator configuration, is a fairly useful tool to obtain simultaneous laser power at different harmonics. The analysis of the system evolution is achieved with two different simulation codes.