Silicon crystalline undulator prototypes: Manufacturing and X-ray characterization

Short-period crystalline undulators have the potential to enable intense and monochromatic sources of hard X and γ radiation. Three crystalline undulators were manufactured and their structural properties were characterized at the ESRF X-ray light source. In particular, a crystalline undulator consists in a periodically bent crystal in which channeled electrons or positrons follow the bending of the crystalline planes, thus generating electromagnetic radiation in analogy with standard magnetic undulators. State-of-the-art magnetic undulators can be built with a period of no less than a few cm. On the other hand, a crystalline undulator could be built with a period down to the sub-mm range. Thus, a crystalline undulator would allow generating harder photons. Since the radiator consists of a small crystal, a crystalline undulator is a valid and low-cost alternative for intense hard radiation production at electron accelerator facilities. The three samples were realized at the INFN laboratory of Ferrara, Italy, through the grooving method, namely a method developed to induce a self-standing and adjustable deformation to a crystal. The samples showed a uniform and sinusoidal curvature, thus proving that the grooving method is suitable for building crystalline undulators.