Positron Source Update Summary from Beijing Positron Source Meeting

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Positron Source UpdateSummary from Beijing
Positron Source Meeting

• I. Bailey
• 28th February 2007
• Liverpool LC Meeting

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Overview of Activity

• Reference Design Report
• Target Hall
• Target Systems
• AMD (not in this summary)
• Undulator (not in this summary)
• Laser Compton (not in this summary)
• Polarisation and accelerator physics
• (http//hirune.kek.jp/mk/ilc/positron/IHEP/)

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Current Design
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Target Hall and Radiation Issues
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Alternative Target Hall Layout

• Micro target hall
• 1 target station
• Surface reprocessing
• 8 of full target-hall size (100m2)

V. Bharadwaj, 17th October 2006
New baseline.
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Target Geometry Drawn in SimpleGEO
Drive shaft(includes water channel)
Target wheel (includes water channel)
5 cell rf cavity.
L. Fernandez-Hernando,DL, 25/01/2007
e.g. s/c OMD

• A few glitches found in exporting geometries
  between SimpleGEO and FLUKA.
• Should be able to begin simulations in a few
  weeks.

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Target Removal/Replacement Showing Storage Cell
M. Woodward, 24th Jan 2007
Beam Pipe
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Estimated Target Changeover Times
M. Woodward, 24th Jan 2007
28 Hours Removal
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Estimated Target Changeover Times
25 Hours Replacement
M. Woodward, 24th Jan 2007
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Target Systems
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Stage 1 Prototype Target Wheel
Sectional view

• 1m diameter wheel with simplified structure
  compared to current baseline target wheel.
• Optional cantilever drive shaft (deflection
  measurements)
• Consistent with water-cooling (to be confirmed by
  LLNL)
• Uses Rigaku ferrofluidic feedthrough and is
  consistent with Deublin water union.
• Motor being sized for rotation up to 2000rpm.

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Stage 1 Prototype Target Wheel and Test Magnet
Sectional view
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Rotating disk experiment
Electra model of copper disk
Variable magnet gap
Permament magnet NdFeB properties defined from
optimiser fit
Conductor initial model copper 1.68e-8Om
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Rotating disk experiment
Eddy currents A/mm2 _at_2000rpm
Unit vectors
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Final model results for all gap spacing's
Rotating disk experiment
Models use 0.75 times conductivity of high cond
copper
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Final model results for all gap spacing's
Rotating disk experiment
Models use 0.75 times conductivity of high cond
copper
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ILC wheel model
Eddys _at_ 2000rpm
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ILC wheel model
Power required to drive wheel _at_ different
rotational speeds Integrate power dissipation in
wheel volume directly in model I2r Model-torque
calculated use this to calc power provided by
braking force Should be equivalent
The large power required to drive the wheel may
pose a problem in the design.
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Polarisation and Accelerator Physics
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Advantage e Polarization

• No doubts 60 e polarization are needed
• What about 30 for the beginning?

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Peff

• Increase of effective polarization

For comparison old LC studies (60,40)? Peff
0.8
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Transverse polarization

• does NOT work with e- polarization only
• sensitivity to new physics (CP violation,
  graviton)

Rizzo
MH1.5 TeV, E500 GeV, L500 fb-1
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Physics goal
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Summary Conclusion

• 30 is benefit for physics
• we could have a polarized machine from the
  beginning!
• Allows test of operation with both beams
  polarized
• ? should be used for physics otherwise it has
  to be destroyed
• (see also slides from L. Malysheva / I.
  Bailey)
• Utilization of low e polarization needs
• - Positron polarization measurement
• - Spin rotation
• frequency? Desired train-by-train
• proposed scheme exists spin rotators
  before (LTR) and
• after the DR (RTL) are needed
  (see SLAC-TN-05-045,
• 
  EUROTeV-Report-2005-024-1)
• other solutions for helicity
  reversal?
• no reversal is worse than no
  polarization!
• Further design simulation work has to be done
  and should include the 30 option
  (depolarisation, polarimeter, spin-flip-frquency
  etc.)

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WP2.3 Recent Progress
Beam-Beam Simulations.

• Obtained first results from applying SLICKTRACK
  to the main linac lattice.
• Implemented first higher-order corrections into
  CAIN beam-beam simulation (see panel on right)
  including final state polarisation.
• Completed theoretical study of approximation used
  for anomalous magnetic moment in T-BMT equation
  implemented in CAIN. This approximation has been
  shown to be valid!
• Compared SLICKTRACK and BMAD simulations for beam
  delivery systems.
• Begun first steps towards long term goal of
  including non-linear transfer maps into
  SLICKTRACK software package.
• Expanding group of collaborators.

Polarised cross-sections for incoherent
Breit-Wheeler pair production added to CAIN
Tony Hartin
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WP2.3 - Remaining Milestones and Future Plans

• The motivation for a complete cradle to grave
  spin tracking simulation has grown as the high
  energy physics community has increasingly
  identified the importance of polarised beams as a
  means to offset any reduction in ILC luminosity.
• This work has been identified as high priority by
  the Global RD board.
• We have simulated most of the machine but not yet
  in a fully integrated fashion.
• We need
• Further development of SLICKTRACK for full
  non-linear spin motion study of BDS and study of
  main linac.
• Further development of positron source simulation
  including effects such as beam jitter and the
  investigation of spin flip techniques.
• Theoretical work on beam-beam interactions.
• A continued rolling study of the whole machine to
  allow optimum use of polarisation as a tool for
  the ILC.