ILC DR ecloud simulations in arcs

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ILC DR ecloud simulations in arcs
M. Pivi (SLAC)
Aug, 2005
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ILC Damping Ring electron cloud studies and
simulations

• At the end of the year 2005, a Damping Ring (DR)
  will be selected amongst the actual 7 different
  damping ring designs. Goal of the DR task force 6
  is to evaluate the electron cloud effect in each
  damping ring circumference range (17km, 6km,
  3km).
• We prioritize simulations starting to focus on
  the three DR designs TESLA 17km, OCS 6km, OTW
  3km. Hopefully we will reach the
  point to simulate the remaining DRs.
• Started benchmarking the electron cloud build-up
  with codes ECLOUD (CERN) and POSINST (SLAC).
• Use common secondary electron yield (SEY)
  model/s. Sensitivity studies.
• Single-bunch instability simulations KEK/CERN

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News

• A. Wolski suggested to use new specifications for
  vacuum camber sizes. This vacuum chamber sizes
  are actually adopted by the rest of task force
  community, and are listed in the paper
• http//www.desy.de/awolski/ILCDR/DRConfiguration
  Study_files/Task3_files/ILCDRVacuum.pdf
• chamber sizes are smaller than previous TESLA
  specifications.
• concern more electron cloud with smaller
  chamber size ? (see simulations below)
• Probably, that is ok for comparative studies
  (?!)

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ILC DR Parameters vacuum chamber (new)
http//www.desy.de/awolski/ILCDR/DRConfigurationS
tudy_files/Task3_files/ILCDRVacuum.pdf
Arc chamber
Wiggler chamber
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ILC DR Parameter
Updated parameters table file on web, with new
vacuum chamber parameters and corrected beam
sizes.
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SEY Models
Secondary Emission Yield Model 1) (variable Emax
and variable e- reflectivity extrapolation
based on LHC Proj.Rep-632, SPS
measurements SR (?!) electron
conditioning) delta_max 1.3 epsilon_max Emax
190 eV (function of delta_max) low-energy
elastic reflectivity of electrons at 1.3
35 delta_max 1.2 epsilon_max Emax 180 eV
(function of delta_max) low-energy elastic
reflectivity of electrons at 1.2 33 delta_max
1.1 epsilon_max Emax 170 eV (function of
delta_max) low-energy elastic reflectivity of
electrons at 1.1 30
Secondary Emission Yield Model 2) (constant Emax
and constant e- reflectivity based on SPS data
and. Hillerets recommendation) delta_max
1.3 epsilon_max Emax 234.75 eV (function of
delta_max) low-energy elastic reflectivity of
electrons at 1.3 50 delta_max 1.2 epsilon_max
Emax 232.38 eV (function of delta_max)
low-energy elastic reflectivity of electrons at
1.2 50 delta_max 1.1 epsilon_max Emax 230 eV
(function of delta_max) low-energy elastic
reflectivity of electrons at 1.1 50
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ILC DR Parameter
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TESLA COMPARE SEY MODELS
arc BEND
arc BEND
SEY MODEL (2)
SEY MODEL (1)
Using POSINST
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OCS DR arc BEND
Threshold at SEY1.2
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OTW DR arc BEND
peak SEY1.0
Threshold at SEYlt1.0. (Electrons spiral in bend
and impinge with a grazing angle increasing the
effective SEY).
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TESLA DR arc DRIFTs
Photoelectrons dominated.
POSINST
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OCS and OTW arc DRIFTs
Clear build-up in OTW
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Compare different chamber sizes
Smaller vacuum chamber radius beneficial in all
configurations.
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Compare in DRs ARC
BEND
arc DRIFT
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OTW density within 10 beam sigma, pinghing effect
End bunch passage
Density before bunch passage
Factor 3-4 pinching
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Electron-cloud thresholds in BENDS of different
rings.
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• SEY MODEL 1 and 2 close results in this
  parameter range.
• TESLA has moderate electron cloud build-up in
  BENDS and is dominated by photoelectrons in arc
  drifts
• OTW has threshold SEYlt1 in bends and clear
  build-up in drifts
• Need ARC quadrupoles and wiggler simulations, to
  compile electron cloud density along all ring.
• Computing short-range wake fields

The deadline is end of October