Positron Yield Optimization by Adjusting the Components Offset and Orientation

The SuperKEKB’s design luminosity is 40 times greater than that of KEKB. In order to achieve this goal, we need to keep the injectionelectronbeam emittancesmall andlet the primary electron beam generates high positron yield. The design is challengebut fulfilled after introducinga pulse-topulse switching system for electron and positron injection. During the operation, the injection electron beam is on axis to preserve emittance and the primary electron beam will be steered to strike on the offset target to generate positrons. The flux concentrator as a part of the matching device in capture section plays an important role in yield improvement. It is offset due to the constrain of small aperture. As a result of the straight cut-in slit section the FC has an unsymmetric field distribution, so that the orientation could lead to a positron yield variation. In this paper, we will discuss this issue and find out the ideal trajectory for the positron beam.