One should pay attention to quite a lot of factors when the emittance of high-current ion beam is measured. The background subtraction and threshold setting,the measuring method of pulsed beam emittance,as well as the error sources in the emittance measurements and its elimination or correction are discussed based on the experience during the R&D of three emittance measurement units for high-current ion beams at Peking University.
To meet the requirements of developing SFRFQ and upgrading the 1 MeV ISR RFQ accelerator,an ECR O^+ ion source and LEBT system have been developed.Using two Einzel Lenses to focus the beam,more than 3mA O^+ beam with the energy of 22keV can be obtained at the end of LEBT.Its normalized root-mean-square emittance is about 0.12πmm·mrad.
