Proposal for an X-Ray Free Electron Laser Oscillator with Intermediate Energy Electron Beam

摘要

Harmonic lasing of low-gain free electron laser oscillators has beenexperimentally demonstrated in the terahertz and infrared regions. Recently,the low-gain oscillator has been reconsidered as a promising candidate for hardx-ray free electron lasers, through the use of high reflectivity, highresolution x-ray crystals. In this letter, it is proposed to utilize acrystal-based cavity resonant at a higher harmonic of the undulator radiation,together with phase shifting, to enable harmonic lasing of the x-ray freeelectron laser oscillator, and hence allow the generation of hard x-rayradiation at a reduced electron beam energy. Results show that fully coherentfree electron laser radiation with megawatt peak power, in the spectral regionof 10-25keV, can be generated with a 3.5GeV electron beam.