Tunable-wavelength production of circularly polarized X-rays with a perfect-crystal quarter-wave plate

Circularly polarized X-rays were produced between 0.14 and 0.16 nm using a perfect-crystal phase retarder in Bragg geometry. Linear polarization of the on-axis synchrotron radiation was converted to circular polarization of the two helicities with degree of circular polarization higher than 0.98.