Radiation emission at channeling of electrons in a strained layer Si1-xGexSi1-xGex undulator crystal

Experiments have been performed at the Mainz Microtron MAMI to explore the radiation emission spectra from a crystalline undulator at electron beam energies of 270 and 855 MeV. The epitaxially grown graded composition strained layer Si1-xGexSi1-xGex undulator had 4-period with a period length λu=9.9μm. Spectra taken at the beam energy of 270 MeV at channeling in the undulating (110) planes exhibit a broad excess yield around the theoretically expected photon energies of 0.069 MeV, as compared with a flat silicon reference crystal. Model calculations on the basis of synchrotron-like radiation emission from finite single arc elements, taking into account also coherence effects, suggest that evidence for a weak undulator effect has been observed for the first time for electrons.