Hollow Electron Beam Collimator: R&D Status Report
  Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams. 
G. Stancari, A. Drozhdin, G. Kuznetsov, V. Shiltsev, A. Valishev, A.   Kabantsev (Fermilab), L. Vorobiev (UC, San Diego)
physics.acc-ph