GSI, Darmstadt
The head-tail instability represents a potential intensity limitation for bunched beams in the synchrotrons of the FAIR project. Parametrical studies with numerical simulations over very long time scales are necessary in order to understand the effect of direct space charge, nonlinear synchrotron oscillations and image charges, which are all important in FAIR synchrotrons. Existing analytic approaches either neglect space charge or describe simplified models, which require a numerical or experimental validation. For our simulation studies we use two different computer codes, HEADTAIL and PATRIC. In this work we verify models for wake-field kicks and space-charge effect using the analytic solution for head-tail mode frequencies and growth rates from the barrier airbag model.
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.
