ELECTRON CLOUD EFFECTS IN THE CERN SPS AND LHC

Electron cloud effects have been recently observed in the CERN SPS in the presence of LHC type proton beams with 25 ns bunch spacing. Above a threshold intensity of about 4 × 1012 protons in 81 consecutive bunches, correspond-ing to half of the nominal ‘batch ’ intensity to be injected into the LHC, an intense electron bombardment gives rise to a strong perturbation of the transverse feedback pick-up signals and to significant pressure rises. Also the intensity and emittance along the bunch train is affected. We com-pare experimental results with simulations of the electron cloud build-up and discuss possible solutions.