Recirculated Wave Undulators for Compact FELs

Particular schemes of Free Electron Lasers (FELs) are designed to exploit wave undulators. We consider a system employing a recirculated electromagnetic undulator provided by a high-power laser in a resonator cavity. The aim is to establish from calculations a set of realizable parameters for such a device. Indeed, novel generation electron accelerators push forward the limits on the accelerating fields, reducing to the sub-meter scale the length over which the electrons can gain enough energy for lasing in the VUV/X-ray region of the electromagnetic spectrum. On the other hand, these innovative technologies do not solve yet the problem associated with the saturation length and therefore of the undulator length, which can be as long as several tens of meters. The option of a FEL based on a wave undulator might provide a valid solution in this respect.