OPTICAL DIFFRACTION RADIATION INTERFERENCE AS A NON-INTERCEPTING EMITTANCE MEASUREMENT FOR HIGH

Conventional intercepting transverse electron beam di-agnostics, as the one based on Optical Transition Radiation (OTR), cannot tolerate high power beams without signifi-cant mechanical damages of the diagnostics device. Opti-cal 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 Inter-ference). In this case the beam goes through slits opened in two metallic foils placed at a distance shorter than the radi-ation 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 re-sult of the first measurements of the beam emittance using ODRI carried out at FLASH (DESY). Our result demon-strates 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