Beamstrahlung on the Septum Blade

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Beamstrahlung on the Septum Blade

• 01.04.2003
• ECFA/DESY Workshop
• Amsterdam

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The Extraction Line Problem
Incoming Beam
Beamstrahlung
Outgoing Beam
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Beamstrahlung Distributions
N. Walker (Prague)
Realistic Beam
Effect of 10 s offset
Expectation Power on septum blade can reach
several kW
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Questions

• Formation of a working group to revisit the
  design of the extraction line. First Meeting on
  December 3rd 2002 identified the following
  questions
• Septum magnet design
• Failure modes
• What power can the thin blade cope with ?
• Reliability of electro-static separators
• IR is a highly charged environment
• Power loss from the charged particle extraction
  ?
• Is a (small or large) crossing angle a solution
  ?
• 800 GeV upgrade
• How much energy is really deposited in the septum
  blade ?

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Disclaimer
All I am going to present is right out of the
press and is therefore to be considered VERY
PRELIMINARY
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Simulating the Extraction Line

• Part of the extraction line included in BRAHMS
• Shadow
• Distance from IP 45m
• 2m long
• 5mm thick
• 7mm vertical distance from nominal beam (156
  µrad)
• Copper
• Septum Blade
• Distance from IP 47m
• 16m long
• 5mm thick
• 7mm vertical distance from nominal beam
• Copper

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Realistic Beams

• Simulation of the complete machine done by Glen
  White.
• Using
• LINAC PLACET (D. Schulte)
• BDS MERLIN (N. Walker)
• Beam-beam GUINEA-PIG (D. Schulte)
• Takes into account
• Simulation of feedback loop
• Orbit injection errors into LINAC
• Wakefield effects in LINAC
• Vibration of quads in BDS
• Energy spread of e- due to undulator
• Resolutions of BPMs
• Jitter on kicker signals
• Beams and backgrounds are available through
  database at
• hepwww.ph.qmul.ac.uk/lcdata

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Nominal Beam

• Total average Beamstrahlung power 360 kW
• Integrated power in septum blade area 60 W

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Realistic Beam

• Feedback system brings beams into stable
  collisions after 100 BX
• Total average Beamstrahlung power 500 kW (TDR
  360 kW !)
• Integrated power in septum blade area 35 kW

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Colliding with the Septum
5 GeV Photon
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Nominal Beam

• Shadow
• Average deposited power 40 W
• Septum blade
• Average deposited power
• 0.3 W

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Realistic Beam

• Shadow
• Average deposited power 15 kW
• Septum blade
• Average deposited power
• 80 W

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Conclusion

• Under realistic beam conditions, 30-40 kW of
  Beamstrahlung are emitted under vertical angles
  larger than 0.155 mrad.
• Roughly half of the emitted energy is deposited
  in the septum shadow.
• Septum blade receives on average 80W.
• Information from Efremov 15 kW has to be cooled
  away from septum blade due to normal operation.
• Septum will probably undergo no mechanical
  damage.
• 40 kW of Beamstrahlung will irradiate the septum
  environment.
• To be done
• Check backgrounds for the detector.
• Backscattering
• Pairs, neutrons with realistic beam
• Check charged particle extraction losses.