X-ray monochromator with an energy resolution of 8×10−9 at 14.41 keV

An ultrahigh-resolution x-ray crystal monochromator providing a 120 μeV bandwidth at 14.41 keV is presented. The design, which uses four independent silicon crystals and has an output beam parallel to the incident beam, may be generalized to arbitrary energies. Fluxes of 1.3×106 photons/s (1.0×107 photons/s) in bandwidths of 120±15 μeV (140±15 μeV) were measured. The performance of the monochromator, including the preservation of coherence through it, was verified by measurement of a 9.6±2.0% enhancement in the coincidence rate (i.e., γ(2)−1=0.096±0.020) in an intensity correlation experiment.