LHC Injectors Upgrade Project: Outlook of the Modifications to the Super Proton Synchrotron (SPS) Vacuum System and Impact on the Operation of the Carbon-Coated Vacuum Chambers

Aiming at doubling the beam intensity and reducing the beam emittance, significant modifications of the LHC and its injector chain will take place during Long Shutdown 2 (LS2), starting from 2019. The LIU project (LHC Injector Upgrade), in the specific, touches Linac4, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS) as well as the heavy ion chain. During LS2, important changes will take place mainly in the Long Straight Sections of the SPS to host a newly conceived dumping system, upgraded RF cavities and upgraded extraction channels. Additionally, the vacuum chambers of the main bending and focusing magnets as well as vacuum drifts will be coated with amorphous carbon in order to reduce the dynamic pressure effects induced by multipacting. The modifications to the different vacuum sectors will be described in details as well as the impact on operation of amorphous carbon coated sectors that have been already deposited.Aiming at doubling the beam intensity and reducing the beam emittance [1], significant modifications of the LHC injector chain will take place during Long Shutdown 2 (LS2), starting from 2019. The LIU project (LHC Injector Upgrade) [2], in the specific, touches Linac4, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS). During LS2, im- portant changes will take place mainly in the Long Straight Sections of the SPS to host a newly conceived dumping system, upgrade RF cavities and the extraction transfer lines. Additionally, the vacuum chambers of some main bending and focusing magnets, as well as vacuum drifts, will be coated with amorphous carbon coating (aC) in or- der to minimise the induced beam instabilities due to elec- tron multipacting[3]. The guidelines followed to conceive and design the new vacuum sectors will be described here- after and a first glance at the impact on the operation of aC coated chambers will be given