Plasma Physics Seminar ( Phys 769)

Dr. Phillip Sprangle, Plasma Physics Division, NRL Laser-Pumped X-ray Free Electron Laser A laser-pumped free-electron laser (FEL) can, in principle, generate coherent, polarized x-rays for applications in research. In a laser-pumped x-ray FEL an intense laser field replaces the magnetic wiggler field of a conventional FEL. Depending on the intensity and quality of both the electron beam and pump laser, the spontaneous incoherent x-rays, generated by Thomson backscattering, can be coherently amplified. In a conventional FEL the generation of x-rays requires electron beam energies in the multi-GeV range. In a laser-pumped x-ray FEL, electron beam energies in the multi-MeV range would be sufficient. To generate coherent x-rays with this mechanism a number of physics and technology issues must be resolved. Foremost among these are the stringent requirements placed on the electron beam quality and brightness as well as the pump laser intensity and energy. The seed radiation for the laser-pumped FEL is the laser induced spontaneous radiation. The evolution of incoherent radiation into coherent radiation as well as the gain lengths associated with the coherent x-rays as a function of electron beam energy spread is analyzed and discussed. These issues, as well as others, necessary to achieve coherent amplified x-rays in a laser-pumped FEL will be addressed. Work supported by NRL and ONR Return to main page