Abstract
The Beijing Electron-Positron Collider (BEPC) will be upgraded to BEPCII, and the luminosity will be about 100 times higher. We developed a three-dimensional strong-strong PIC code to study the beam-beam effects in BEPCII. The transportation through the arc is the same as that in Hirata's weak-strong code. The beam-beam force is computed directly by solving the Poisson equation using the Fourier analysis and cyclic reduction method, and the boundary potential is computed by circular convolution. The finite bunch length effect is included by longitudinal slices. An interpolation scheme is used to reduce the required slice number in simulations. The standard message passing interface is used to parallelize the code. The computing time increases linearly with (n+1), where n is the slice number. The calculated luminosity of BEPCII at the design working point is similar to 50% of the design value. The best area in the tune space is near (0.505,0.57) according to the survey, where the luminosity is similar to 80% of the design.
Highlights
The Beijing Electron-Positron Collider (BEPC) was constructed for both high energy physics and synchrotron radiation (SR) researches
Following the success of the KEK B factory (KEKB), the crossing scheme was adopted in BEPCII, where two beams collide with a horizontal crossing angle of 2 11 mrad
The beam-beam force experienced by the particle is computed with following steps: (a) it is drifted to the longitudinal position s and triangularshaped cloud (TSC) weights on nine nearest points are calculated; (b) the potentials on twenty-five nearest points are calculated by interpolation; (c) the transverse field strength on nine nearest points is calculated by six-point difference scheme; (d) the field experienced by the particle is calculated by using the weighted summation of the fields at nine nearest points with the TSC weight
Summary
The Beijing Electron-Positron Collider (BEPC) was constructed for both high energy physics and synchrotron radiation (SR) researches. BEPCII is an upgrade scheme from BEPC. The beam-beam interaction is one of the most important limiting factors to determine the luminosity of storage ring colliders. The weak-strong simulation, which is not self-consistent, has been employed in order to simulate the effect in a reasonable computing time. The two-dimensional simulation without finite bunch length effect can be done using a personal computer in a reasonable time, while a supercomputer is still necessary in the three-dimensional strong-strong simulation. The strong-strong codes have a reliable predictive capability of realistic beam-beam interaction and the simulation results show a good quantitative agreement with the experimental observations [8].
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