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

Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Presented at North American Particle Accelerator Conference (NA PAC 2013): North American Particle Accelerator Conference. Pasadena, CA, USA, 29 Sep - 4 Oct 2013.
Country of Publication:
United States

Citation Formats

Stancari, G. Collimation with hollow electron beams: a proposed design for the LHC upgrade.. United States: N. p., 2013. Web.
Stancari, G. Collimation with hollow electron beams: a proposed design for the LHC upgrade.. United States.
Stancari, G. 2013. "Collimation with hollow electron beams: a proposed design for the LHC upgrade.". United States. doi:.
title = {Collimation with hollow electron beams: a proposed design for the LHC upgrade.},
author = {Stancari, G.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2013,
month = 9

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  • Electron lenses built and installed in the Tevatron have proven themselves as safe and very reliable instruments which can be effectively used in hadron collider operation for a number of applications, including compensation of beam-beam effects [1], a DC beam removal from abort gaps [2], and as a versatile diagnostic tool. In this article, we--following the original proposal [3,4]--consider in more detail a possibility of using electron lenses with hollow electron beam for ion and proton collimation in LHC and the Tevatron.
  • 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 instabilitiesmore » of the overlapping proton and electron beams.« less
  • Recent experimental studies at the Fermilab Tevatron collider have shown that magnetically confined hollow electron beams can act as a new kind of collimator for high-intensity beams in storage rings. In a hollow electron beam collimator, electrons enclose the circulating beam. Their electric charge kicks halo particles transversely. If their distribution is axially symmetric, the beam core is unaffected. This device is complementary to conventional two-stage collimation systems: the electron beam can be placed arbitrarily close to the circulating beam; and particle removal is smooth, so that the device is a diffusion enhancer rather than a hard aperture limitation. Themore » concept was tested in the Tevatron collider using a hollow electron gun installed in one of the existing electron lenses. We describe some of the technical aspects of hollow-beam scraping and the results of recent measurements.« less
  • This thesis work was carried out in the framework of the U.S. LHC Accelerator Research Program (USLARP), a collaboration between the European Organization for Nuclear Research (CERN) and the U.S. Department of Energy. The first half of the work was completed at Fermilab (USA), the location of the Tevatron, a proton-antiproton collider and the second largest particle collider in the world. The second half was completed at CERN (Switzerland), the location of the largest proton collider in the world (Large Hadron Collider (LHC)). This thesis characterizes a Hollow Electron Beam (HEB) for possible usage at the LHC to enhance itsmore » collimation through Hollow Electron Beam Lenses (HEBLs). Collimation is a long established principle in high energy particle accelerators. Hollow Electron Beam Collimation (HEBC) aims to enhance current collimation systems by controlling diffusion of primary halo particles into the limiting aperture. It works on the principle of a transverse radial electric field that kicks the primary halo particles outwards upon each pass in a multi-pass system. The transverse field is produced by a HEB that is coaxially aligned with the accelerator beam, producing a negligible electric field in the center and a strong transverse electric field at amplitudes higher than the inner radius of the electron beam. Ideally, halo particles are affected without perturbation of the beam core. One of the main advantages of this system is to decrease the dependence on instantaneous loss spikes and beam jitter. A solid experimental basis of HEBC was accumulated at the Tevatron. The application of this technique at the LHC is now under investigation. The aim of this thesis is to present a preliminary report to support a future optimal conceptual design report. It characterizes the available hardware in order to facilitate the design of a Hollow Electron Gun (HEG) for the LHC, characterizes the effect on beam diffusion by determining the transverse electric fields of the electron beam and initiates 3D simulations in order to determine the effect of the HEBL on the beam core. Experiments were conducted in the Tevatron Electron Lens Test Stand (TELTS) at Fermi National Accelerator Lab (Fermilab) (USA) in the lower Linear Accelerator (LINAC) gallery.« less
  • The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z Phase II collimators. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. Design issues include: (1) Collimator jaw deflection due to heating and sagitta must be small when operated in the steady state condition, (2) Collimator jaws must withstand transitory periods of high beam impaction with no permanent damage, (3) Jaws must recover from accident scenariomore » where up to 8 full intensity beam pulses impact on the jaw surface and (4) The beam impedance contribution due to the collimators must be small to minimize coherent beam instabilities. This paper reports on recent updates to the design and testing.« less