Electron Cloud Effects

Secondary electron emission in combination with the elecromagnetic fields generated by a bunched beam can lead to the formation of electron clouds in the beam chambers of particle accelerators. The interaction of the circulating beam with the e-cloud can lead to transverse instabilities, beam losses, transverse emittance degradation. Moreover, the electrons impacting on the chamber's walls induce other unwanted effects like energy deposition (particularly critical for superconducting machines) and vacuum degradation. This contribution summarizes the mechanisms leading to the formation of the e-cloud, the effects that it can have on the performance of an accelerator, the methods employed to study the phenomenon and different techniques that have been developed to reduce or suppress its formation.