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Smith, J.C.

Paper Title Page
WE6RFP030 Recent Progress on the Design of a Rotatable Copper Collimator for the LHC Collimation Upgrade 2853
 
  • J.C. Smith, L. Keller, S.A. Lundgren, T.W. Markiewicz
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  
 

Funding: Work supported in part by the U.S. Department of Energy contract DE-AC02-76SF00515


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 sagita 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 scenario where up to 7 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. The current design will be presented.

  
WE6RFP031 Prospects for Integrating a Hollow Electron Lens into the LHC Collimation System 2856
 
  • J.C. Smith
    SLAC, Menlo Park, California
  • R.W. Assmann, V.P. Previtali
    CERN, Geneva
  • V.D. Shiltsev, A. Valishev
    Fermilab, Batavia
  
 

Funding: Work supported in part by the U.S. Department of Energy contract DE-AC02-76SF00515


It has been proposed to use a hollow electron lens with the LHC beam collimation system*. The hollow electron beam would be used as a beam scraper and positioned at a closer σ than the primary collimators to increase the halo particle diffusion rate striking the primaries. In this paper we use multi-turn beam tracking simulations to analyze the effectiveness of such a lens when integrated into the LHC collimation system.


*Shiltsez, V. et al. "LHC Particle Collimation by Hallow Electron Beams," Proceedings EPAC08, MOPC098 (2008)

  
TH5PFP089 Trapped Mode Study for a Rotatable Collimator Design for the LHC Upgrade 3416
 
  • L. Xiao, C.-K. Ng, J.C. Smith
    SLAC, Menlo Park, California
  • F. Caspers
    CERN, Geneva
  
 

Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.


A rotatable collimator is proposed for the LHC phase II collimation upgrade. When the beam crosses the collimator, trapped modes will be excited that result in beam energy loss and collimator power dissipation. Some of the trapped modes can also generate transverse kick on the beam and affect the beam operation. In this paper the parallel eigensolver code Omega3P is used to search for all the trapped modes below 2GHz in the collimator, including longitudinal modes and transverse modes. The loss factors and kick factors of the trapped modes are calculated as function of the jaw positions. The amplitude ratio between transverse and longitudinal trapped mode intensity can be used as a direct measure of the position of the beam. We present simulation results and discuss the results.