Emittance measurement by using Duo image pattern of Cherenkov radiation

The emittance of the electron beam is to be measured by using Cherenkov radiation in a novel way. The image patterns of the radiation are formed both in the focal plane and image plane of an achromatic lens with long focus. Both the angular spread and radial distribution of the e-beam are obtained by processing both patterns and in this way the beam RMS emittance is directly resulted. Combining this technology with computerized tomography (CT), the actual particle density distribution in transverse phase space can be determined without any preassumptions. The emittance of the electron beam from the DC-SC photoinjector of Peking University is simulated and a He-Ne laser experiment is presented and discussed in this paper.