Electron Cloud Effects at Positron/Electron (e+/e-) Machines and Electron Cloud Diagnostics

Background electrons are ubiquitous in high-intensity particle accelerators. Under certain operating conditions, amplification of the electron cloud can occur. The beam-cloud interaction can seriously degrade the accelerator performance with effects that range from vacuum degradation to collective beam instabilities. Although electron cloud effects (ECEs) were first observed 20 years ago in a proton ring, in recent years, they have been widely observed and intensely studied in e+/erings. This paper will focus on describing electron cloud diagnostics, which have led to an enhanced understanding of ECEs, especially details of beam-induced multipacting and saturation of the cloud. Such experimental results can be used to provide realistic limits on key input parameters for modeling efforts.