KEK, Ibaraki
Recent progress of KEKB and nano beam scheme adopted in KEKB upgrade are discussed. For the present KEKB, chromatic x-y coupling, which was the key parameter to improve luminosity, is focussed. Beam-beam simulations with weak-strong and strong-strong models for nano beam scheme are presented. A weak-strong simulation was done in the presencee of the longitudinal micro-wave instability. Finally status of beam simulations in KEK supercomputers is presented.
IHEP Beijing, Beijing
The luminosity of BEPCII (the upgrade project of Beijing electron-positron collider) have reached 3.0× 1032 cm-2s-1@1.89GeV in May 2009. In this papaer we'll compare the beam-beam simulation results with the real machine. In the case the single bunch current is lower than 8mA, the simulation concides well with the real. Some phenomenon related to synchro-betatron resonances during machine tuning and simulation is shown. The tune is close to half integer help us increase luminosity, however the detector background increases at the same time. It is believed that the beam-beam dynamic effect result in the drop of the dynamic aperture. We also study the possible luminosity contribution from the crab waist scheme in BEPCII.
