2nd ILC Acc. Workshop

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BCD ILC Cryomodule from Type III

• Take TTF Type III as reference conceptual design
• Introduce layout modifications required to fit
  ILC requirements
• Quadrupole/BPM package at the center (symmetry
  and stability)
• Review pipe sizes/positions according to gradient
  and cryo-distribution
• Consider/include movers (warm) at the center post
  for x,y quadrupole beam based alignment
• Consider/include movers on the cryomodule
  supports to optimize the module centering
  according to HOM data
• Review suspension system (post, etc.) for
  stability and transport
• Review all the subcomponent design for production
  cost and MTBF
• Materials, welds, subcomponent engineering, LMI
  blankets, feed-through, diagnostics and cables,
  etc.
• Module assembly issues
• Reduce the waste space between cavities for real
  estate gradient
• Flange interconnection, tuners, etc.
• Define all the QC and QA steps required to assure
  MTBF

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ACD Alternative for Quadrupole

• Independent Cryomodule for the Quad proposed by
  SLAC
• Pros
• To be analyzed wrt the upgrade of TTF 3 with
  movers
• Cons
• More expensive Valves, independent He supply and
  return, etc.
• Consistent impact on real estate gradient because
  of vacuum valves and unavoidable bellows 2 x 350
  mm at least i.e. 0.5 km/linac ( 25 M/linac)

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Q20 of Cavities per Cryomodules

• From 8 to 12 is acceptable without major design
  changes
• Cryomodule does not have strong reasons to prefer
  one specific number
• Vacuum vessel and HeGRP thickness can be adjusted
  to improve momentum of inertia in a longer
  module Constant deformation
• Cost impact on the linac was studied with
  industry for TDR and the result was that the
  effect should be in within the error bar because
  of pros and cons
• Module assembling slightly less expensive but
  handling and transport is more
• Module reference milling machining more expensive
• Decision drivers
• RF Distribution Cavities/Klystron and wave-guide
  distribution scheme
• Modest impact on real estate gradient and tunnel
  length
• The impact of each module interconnection is at
  present 380 mm and cannot be decreased
  substantially because it includes vacuum valves,
  He retourn connection and 70 K HOM absorber
• At 30 MV/m gradient the impact on linac length
  is
• 55 m (10) or 136 m (8)

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Q31 Linac Cavity Spacing

• As short as possible!
• Electromagnetic constraint for 70 mm beam pipe
  ca. 180 mm
• TTF 3 Spacing 3?/2 i.e. gt 340 mm !
• TESLA TDR Spacing 283 mm
• There is a lot of margin for improvement
• Each cm saved as an impact of 85 m on the length
  of each linac
• BCD should be based on 250 mm gt 750 m/linac
  saved
• ABD could be the work for 180 mm gt 1,3 km /linac
  saved

TTF Cavity Interconnection 340 mm between irises