Gou, WP (reprint author), CAS, Inst High Energy Phys, Beijing 100039, Peoples R China.
The positron yield is a very important parameter for positron source, and directly symbolizes the quality of an e(+) accelerator. Now BEPC is planned to be upgraded into BEPC II, many parameters of positron source should be greatly improved to meet the requirements of intense e(+) beam injection. We will optimize each section of the positron source to get the highest yield. EGS4 and PARMELA codes are used for positron source design. We use EGS4 code to simulate the electron-gamma shower of high-energy electrons in a medium, optimize target thickness, and analyze positron distributions in phase space. We discuss the positron yield's dependence on some system parameters. Then we use PARMELA code to track and simulate particle motion in the matching, focusing and accelerating systems,discuss how to choose capture section RF phase. Finally we get a reasonable positron yield at the end of positron source.