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WG3b Damping ring

WG3b Damping ring. K. Ohmi. Beam parameters in the damping ring. Lattice. TESLA, OTW OCS. Fill pattern (500MHz 650MHz). Aperture. Vertical emittance and misalignment. Design e y =20 nm. Resistive wall impedance.

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WG3b Damping ring

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  1. WG3b Damping ring K. Ohmi

  2. Beam parameters in the damping ring

  3. Lattice • TESLA, OTW OCS

  4. Fill pattern (500MHz 650MHz)

  5. Aperture

  6. Vertical emittance and misalignment • Design ey=20 nm

  7. Resistive wall impedance • Resistive wall wake integrated along the ring with considering chamber radius and beta function.

  8. Broad band impedance • Longitudinal • Transverse

  9. Single bunch instability • Longitudinal unstable, bunch lengthing • Transverse stable

  10. Coupled bunch instability • Transverse bunch by bunch feedback system, 15 turn. • Longitudinal, no problem (KEKB type SC cav.).

  11. Intrabeam scattering

  12. Space charge effect • TESLA, no problem (the coupling bump is required). • OCS(6km), no problem • BRU(6km,3.7GeV), serious. • Structure resonances should be avoided. TESLA OCS BRU

  13. Electron cloud effect Table 1. Electron cloud density near beam (m-3) before bunch passage, compared with threshold density for secondary electron yield d2,max=1.2.

  14. Ion cloud effect • Mini gap, • Growth time ~10 turn. • Tune shift.

  15. Kicker • Rise/fall time ~3ns is achieved for a conventional strip-line kicker. • Base line: strip-line, alternative: RF sep. Fourier.

  16. Other technical issues • RF cavity frequency 500MHz, super (base) or normal (alt.) • Wiggler super (base) or normal (alt.) • Magnet normal (base) or permanent (alt.) • Vacuum choice of pipe radius, shape, material, coating. • Instrumentation monitor, feedback

  17. Circumference Alt. Base line

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