BEPC II positron source

BEPC II - an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e(+)e(-) collider. The fundamental requirements for its injector linac are the beam energy or 1.89GeV for on-energy injection and a 40mA positron beam current at the. linac end with a low beam emittance of 1.6 mu m and a low energy spread of +/- 0.5% so as to guarantee a higher injection rate (>= 50mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, we will increase the electron gun current front 4A to 10A by using a new electron gun system and increase the primary electron energy from 120MeV to 240MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac front the electron gun to the positron source has been installed into the tunnel. In what follows, we will emphasize the positron source design, manufacture and tests.