WP12: Vacuum & Beam Screen

WP12: Vacuum & Beam Screen

WP12 is in charge of producing several sets of new equipment and vacuum layouts in full compliance with the HL-LHC beam parameters to guarantee a stable vacuum, to satisfy the vacuum life time and to reduce the beam induced background in the LHC Experiments to acceptable levels. It contributes also to the design and production of vacuum system by other WPs.

The main task of WP12 is to produce a new, perforated beam screen which optimises the beam aperture and provides enough shielding to adsorb at 60-80 K the collision debris produced at the interaction point in order to protect the superconducting magnets. To comply with machine requirements in terms of beam physics, vacuum and machine protection the new beam screen is designed with tungsten shielding, octagonal aperture and amorphous carbon coating. The insulation vacuum system of the new cryostats will follow the LHC standards.

The positions of mechanical supports, pumps, gauges, sector valves, vacuum modules etc. ensure that layouts along the long straight sections are optimised in view of the new machine configuration and in full compliance with the ALARA approach, including the functionalities for the Full Remote Alignment System. All room temperature vacuum and experimental chambers need to be bakeable and NEG coated to provide pumping speed and minimise the secondary electron yield (SEY), thus mitigating electron cloud effects.

The upgrade of the triplet-forward region of CMS and ATLAS experiments to cope with the increasing radiation dose is also under the mandate of WP12, requiring a newly designed vacuum instrumentation system which can be remotely controlled and connected/disconnected in full compliance with the ALARA approach.

Finally, the new HL-LHC beams and the increased luminosities at ALICE and LHCb impose a new limitation on the triplet/D1 assemblies originating from increased electron cloud driven heat load on the beam screens. In-situ amorphous carbon coating of the inner surface of these beam screens will have to be applied to hamper the electron multipacting and thereby strongly reduce the electron cloud induced heat load.