ILC beam parameters

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ILC beam parameters

• Rob Appleby
• Manchester group meeting
• 20th November 2006

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Luminosity Aiming for 2x1034
Collider luminosity (cm-2 s-1) isapproximately
given by where nb bunches / trainN
particles per bunchfrep repetition
frequencyA beam cross-section at IPHD
beam-beam enhancement factor For a Gaussian beam
distribution
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Luminosity

• frep nb tends to be low in a linear collider
• Fortunately the beam-beam tune shift limit is
  much looser in a linear collider than a storage
  rings and achieve luminosity with spot size and
  bunch charge
• Small spots mean small emittances and small
  betassx sqrt(bx ex)

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Linear Collider Luminosity

• Convert luminosity expression using beam power
• Pbeam ? Ecms N nb frep ? PAC
• Required to have large beam powers
• Forced into strong focusing when the beams
  collide
• Further constrained by IP beam-beam effects
• Beamstrahlung synchrotron radiation due to
  strong beam fields
• Disruption beam distortion due to strong beam
  fields at the IP
• Hourglass b sz
• For flat beams (Maximise L and
• minimise ?B gives sx gtgt sy)where d? N2/sx2sz

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ILC parameters (500 GeV machine)
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Summary

• The parameter sets are luminosity driven and
  designed to meet the machine goals
• The different sets probe various corners of
  parameter space and are meant to be
  representative of possible machine operating
  scenarios
• The 500 GeV machine parameter are shown here -
  the 1 TeV machine sets can be found in the 2004
  ILC parameters document by Tor Raubenheimer
• What is happening now?
• Move to collapse parameter space to point
• Decouple Low Power set into two parts
• Reduction of linac power (Klystrons / 2)
• Increased focusing of beam at the IP
• The first of these is favored in ILC baseline
  machine, and is attractive as the missing
  klystrons can be added later (i.e. reversible
  machine change). Is likely to happen soon!
  Luminosity?