NON-INTERCEPTING EMITTANCE MEASUREMENTS BY MEANS OFudOPTICAL DIFFRACTION RADIATION INTERFERENCE FOR HIGHudBRIGHTNESS ELECTRON BEAM

摘要

Conventional intercepting transverse electron beam diagnostics,ude.g. based on Optical Transition Radiationud(OTR), cannot tolerate high power beams without significantudmechanical damages of the diagnostics device. OpticaludDiffraction Radiation (ODR) is an excellent candidateudfor the measurements of the transverse phase space parametersudin a non-interceptingway. One of themain limitationsudof this method is the low signal to noise ratio, mainly dueudto the unavoidable synchrotron radiation background. Thisudproblem can be overcome by using ODRI (Optical DiffractionudRadiation Interference). In this case the beam goesudthrough two slits opened in metallic foils, placed at a distanceudshorter than the radiation formation zone. Due toudthe shielding effect of the first screen a nearly backgroundfreeudODR interference pattern can be measured allowingudthe determination of the beam size and the angular divergence.udHere we report the preliminary result of the firstudmeasurements of the beam emittance using ODRI carriedudout at FLASH (DESY, Germany). Our result demonstrateudthe unique potential of this technique.