Collimation with hollow electron beams is a technique for halo control inhigh-power hadron beams. It is based on an electron beam (possibly pulsed ormodulated in intensity) guided by strong axial magnetic fields which overlapswith the circulating beam in a short section of the ring. The concept wastested experimentally at the Fermilab Tevatron collider using a hollow electrongun installed in one of the Tevatron electron lenses. Within the US LHCAccelerator Research Program (LARP) and the European FP7 HiLumi LHC DesignStudy, we are proposing a conceptual design for applying this technique to theLarge Hadron Collider at CERN. A prototype hollow electron gun for the LHC wasbuilt and tested. The expected performance of the hollow electron beamcollimator was based on Tevatron experiments and on numerical trackingsimulations. Halo removal rates and enhancements of halo diffusivity wereestimated as a function of beam and lattice parameters. Proton beam corelifetimes and emittance growth rates were checked to ensure that undesiredeffects were suppressed. Hardware specifications were based on the Tevatrondevices and on preliminary engineering integration studies in the LHC machine.Required resources and a possible timeline were also outlined, together with abrief discussion of alternative halo-removal schemes and of other possible usesof electron lenses to improve the performance of the LHC.
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