Phase plates for x-ray optics

In x-ray spectroscopies, it is essential to have a full control of the polarization of the incident photons and x-ray phase plates have become in these recent years a key optical element of a beam line. The principle of x-ray phase plates which originates in the dynamical propagation of x-rays at Bragg diffraction is viewed and the different setups which have been experimented are presented. We will concentrate on the very convenient setup which uses the forward-diffracted beam outside the Bragg diffraction peak and diamond crystals. Applications to the production of circularly polarized x-ray beams, polarimetry measurements and x-ray magnetic linear dichroism are then described.