Optical diffraction radiation interference as a non-intercepting emittance measurement for high brightness and high repetition rate electron beam

Conventional intercepting transverse electron beam diagnostics, as the one based on Optical Transition Radiation (OTR), cannot tolerate high power beams without signifi- cant mechanical damages of the diagnostics device. Optical Diffraction Radiation (ODR), instead, is an excellent candidate for the measurements of the transverse phase space parameters in a non-intercepting way. One of the main limitations of this method is the low signal to noise ratio, mainly due to the synchrotron radiation background. This problem can be overcome by using ODRI (ODR Interference). In this case the beam goes through slits opened in two metallic foils placed at a distance shorter than the radiation formation zone. Due to the shielding effect of the first screen a nearly background-free ODR interference pattern can be measured allowing the determination of the beam size and the angular divergence. We report here the result of the first measurements of the beam emittance using ODRI carried out at FLASH (DESY). Our result demonstrates the potential of this technique suitable to be used as non-intercepting diagnostic for accelerators operated with high brightness and high repetition rate electron beams.