A table-top X-ray FEL based on the laser wakefield accelerator-undulator system

Laser wakefield acceleration makes it possible to build a compact electron linac. While acceleration is attributed to longitudinal wakefields, transverse wakefields simultaneously generated by a short laser pulse can serve as a plasma undulator with a very short wavelength equal to half of the plasma wavelength. We propose a new FEL concept for X-rays based on a laser pulses delivered from a table-top terawatt laser. The system is composed of the accelerator and undulator stages in a table-top size. A low energy electron beam is accelerated due to laser wakefields in the accelerator stage. A bunched electron beam travelling to the opposite direction of driving laser pulses produces a coherent X-ray radiation in the undulator stage. A practical configuration and its analysis are presented.