A Proposal for an X-Ray Free-Electron Laser Oscillator with an Energy-Recovery Linac

We show that a free-electron laser oscillator generating x rays with wavelengths of about 1 Å is feasible using ultralow emittance electron beams of a multi-GeV energy-recovery linac, combined with a low-loss crystal cavity. The device will produce x-ray pulses with ${10}^9$ photons at a repetition rate of 1–100 MHz. The pulses are temporarily and transversely coherent, with a rms bandwidth of about 2 meV, and rms pulse length of about 1 ps.

Figure 1

Reflectivity and transmissivity of x rays at normal incidence to the $(00030)$ atomic planes in $\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3$. Crystal temperature $T=30\mathrm{K}$, $E_0=14.326\mathrm{keV}$. The calculations have been performed using dynamical diffraction theory with the crystal data as in [12].

Figure 2

Schemes of x-ray cavities.

Figure 3

Evolution of intracavity peak power for the case corresponding to the first row in Table .