During the current run of an electron-positron collider DAFNE special electrodes for electron cloud suppression have been inserted in all dipole and wiggler magnets of the positron ring. In this paper we discuss the impact of these electrodes on beam
dynamics and overall collider performance. In particular we report results of measurements such as e-cloud instabilities growth rate, transverse beam size variation, tune shifts along the bunch train etc. with the electrodes switched on and off that clearly indicate the effectiveness of the electrodes for e-cloud suppression.
In DA{Phi}NE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed,
with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of approx 600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using both a commercial spectrum analyzer and the diagnostics capabilities of the DA{Phi}NE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DA{Phi}NE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.
The Phi-factory DAFNE was upgraded in the second half of 2007 in order to implement a recently proposed scheme of crab waist collisions aimed at substantial luminosity increase. Commissioning of the modified collider started in November 2007. In this
paper we briefly describe the crab waist collision concept and discuss in detail the DAFNE hardware upgrade and obtained experimental results.
Since several years the DAFNE Team has been discussing ideas and performing experimental activities aimed at the collider luminosity increase. In this paper we briefly describe the proposed ideas and discuss results of the most relevant beam dynamics
experimental studies that have been carried at DAFNE. We also introduce the concept of crab waist collisions that is the base of the undergoing DAFNE upgrade.
Numerical simulations have shown that the recently proposed crab waist scheme of beam-beam collisions can substantially boost the luminosity of existing and future electron-positron colliders. In this paper we describe the crab waist concept and disc
uss potential advantages that such a scheme can provide. We also present the results of beam-beam simulations for the two currently proposed projects based on the crab waist scheme: the DAFNE upgrade and the Super B-factory project.
