NON-INTERCEPTING EMITTANCE MEASUREMENTS BY MEANS OF OPTICAL DIFFRACTION RADIATION INTERFERENCE FOR HIGH BRIGHTNESS ELECTRON BEAM

Conventional intercepting transverse electron beam diagnostics, e.g. based on Optical Transition Radiation (OTR), cannot tolerate high power beams without significant mechanical damages of the diagnostics device. Optical Diffraction Radiation (ODR) is an excellent candidate for the measurements of the transverse phase space parameters in a non-interceptingway. One of themain limitations of this method is the low signal to noise ratio, mainly due to the unavoidable synchrotron radiation background. This problem can be overcome by using ODRI (Optical Diffraction Radiation Interference). In this case the beam goes through two slits opened in metallic foils, placed at a distance shorter than the radiation formation zone. Due to the shielding effect of the first screen a nearly backgroundfree ODR interference pattern can be measured allowing the determination of the beam size and the angular divergence. Here we report the preliminary result of the first measurements of the beam emittance using ODRI carried out at FLASH (DESY, Germany). Our result demonstrate the unique potential of this technique.