The electron cloud in vacuum pipes of accelerators of positively charged
particle beams causes a beam energy loss which could be estimated from the
synchronous phase. Measurements done with beams of 75 ns, 50 ns, and 25 ns
bunch spacing in the LHC for some fills in 2010 and 2011 show that the average
energy loss depends on the total beam intensity in the ring. Later measurements
during the scrubbing run with 50 ns beams show the reduction of the electron
cloud due to scrubbing. Finally, measurements of the individual bunch phase
give us information about the electron cloud build-up inside the batch and from
batch to batch.Comment: Presented at ECLOUD'12: Joint INFN-CERN-EuCARD-AccNet Workshop on
Electron-Cloud Effects, La Biodola, Isola d'Elba, Italy, 5-9 June 201