Mitigation of coherent beam instabilities (MCBI) for CERN LIU and HL-LHC


  • G. Rumolo



The high-luminosity upgrade of the Large Hadron Collider (HL-LHC) will meet its future yearly integrated luminosity target by means of performance improving upgrades of the LHC itself as well as by receiving significantly higher beam current and brightness from its injectors. The implications of the pushed beam parameters are twofold. On one side, all the accelerators of the LHC injection chain will have to be upgraded to produce the desired beam parameters. For this purpose, the LHC Injectors Upgrade (LIU) program has been established to implement all the needed modifications for meeting the required beam specifications. These upgrades will target the mitigation of coherent beam instabilities and space charge in the injectors, which will allow lifting their existing intensity and brightness limitations to the desired extent. On the other side, the LHC will have to be able to accept the new beam parameters and exploit them at best to produce the integrated luminosity target. This will mainly require control of impedance driven instabilities, beam-beam effects and electron cloud in the LHC itself. In this paper, we will focus on proton beams by describing the identified performance limitations of the LHC and its injectors, as well as the actions envisioned to overcome them.