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ILC DR ecloud simulations in arcs M. Pivi (SLAC)

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

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ILC DR ecloud simulations in arcs M. Pivi (SLAC)

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  1. ILC DR ecloud simulations in arcs M. Pivi (SLAC) Aug, 2005

  2. 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

  3. 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/DRConfigurationStudy_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 (?!)

  4. ILC DR Parameters vacuum chamber (new) http://www.desy.de/~awolski/ILCDR/DRConfigurationStudy_files/Task3_files/ILCDRVacuum.pdf Arc chamber Wiggler chamber

  5. ILC DR Parameter Updated “parameters table” file on web, with new vacuum chamber parameters and corrected beam sizes.

  6. 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. Hilleret’s 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%

  7. ILC DR Parameter

  8. TESLA: COMPARE SEY MODELS arc BEND arc BEND SEY MODEL (2) SEY MODEL (1) Using POSINST

  9. OCS DR arc BEND Threshold at SEY~1.2

  10. OTW DR arc BEND peak SEY=1.0 Threshold at SEY<1.0. (Electrons spiral in bend and impinge with a grazing angle increasing the effective SEY).

  11. TESLA DR arc DRIFTs Photoelectrons dominated. POSINST

  12. OCS and OTW arc DRIFTs Clear build-up in OTW

  13. Compare different chamber sizes Smaller vacuum chamber radius beneficial in all configurations.

  14. Compare in DRs ARC BEND arc DRIFT

  15. OTW: density within 10 beam sigma, pinghing effect End bunch passage Density before bunch passage Factor 3-4 pinching

  16. Electron-cloud thresholds in BENDS of different rings.

  17. 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 SEY<1 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 …

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