Search

We report on the realization of an extremely sensitive x-ray polarization microscope, allowing to detect tiniest polarization changes of 1 in 100 billion (10 ^−11 ) with a μ m-size focused beam. The extreme degree of polarization purity places the most stringent requirements on the orientation of the polarizer and analyzer crystals as well as the composition and the form fidelity of the lenses, which must not exhibit any birefringence. The results show that these requirements are currently only met by polymer lenses. Highly sensitive scanning x-ray polarization microscopy thus is established as a new method. It can provide new insights in a wide range of applications ranging from quantum electrodynamics and quantum optics to x-ray spectroscopy, materials research, and laser physics.

Accurate spectroscopy of highly-charged high- Z ions in a storage ring is demonstrated to be feasible by the use of specially adapted crystal optics. The method has been applied for the measurement of the 1 s Lamb shift in hydrogen-like gold (Au ^+78 ) in a storage ring through spectroscopy of the Lyman x-rays. This measurement represents the first result obtained for a high- Z element using high-resolution wavelength-dispersive spectroscopy in the hard x-ray regime, paving the way for sensitivity to higher-order QED effects.