Collimation with hollow electron beams: a proposed design for the LHC upgrade

Collimation with hollow electron beams is a technique for halo removal in high-power hadron beams. The concept was tested experimentally at the Fermilab Tevatron collider using a hollow electron gun installed in one of the Tevatron electron lenses. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, we are investigating the applicability of this technique to the Large Hadron Collider and a conceptual design is being developed. We review some of the main topics related to this study: motivation; halo removal processes; development of hollow electron guns; effects on the proton beam core; and integration in the LHC machine.