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Nominal PS beam for the future LHC Electron cloud build-up visible on electrostatic pick-ups

OBSERVATIONS OF ELECTRON CLOUD BUILD-UP IN THE CERN PS. R. Cappi, E. Metral, G. Metral, M. Giovannozzi SPS Studies Working Group meeting. Nominal PS beam for the future LHC Electron cloud build-up visible on electrostatic pick-ups Effect of a solenoidal field

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Nominal PS beam for the future LHC Electron cloud build-up visible on electrostatic pick-ups

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  1. OBSERVATIONS OF ELECTRON CLOUD BUILD-UP IN THE CERN PS R. Cappi, E. Metral, G. Metral, M. GiovannozziSPS Studies Working Group meeting • Nominal PS beam for the future LHC • Electron cloud build-up visible on electrostatic pick-ups • Effect of a solenoidal field • Effect of a gap in the bunch train • Simulations by F. Zimmermann • Next studies

  2. Nominal PS beam for the furture LHC (1/6) Magnetic field and double-batch injection

  3. Nominal PS beam for the furture LHC (2/6) Normalised transverse emittances at 1  inj2 - 10ms C1360 inj2 + 5ms C1375 inj1 +10ms C180 ej - 6ms C2389 without bunch rotation ! PSB TT2

  4. Nominal PS beam for the furture LHC (3/6) RF gymnastics • At low energy (1.4 GeV kinetic energy) • 1st injection => 3 bunches (H7) • 2nd injection => 3 bunches (H7) • Triple splitting => 6 × 3 = 18 bunches (H21) • At high energy (26 GeV/c momentum) • 1st double splitting => 18 × 2 = 36 bunches (H42) • 2nd double splitting => 36 × 2 = 72 bunches (H84) with • Bunch rotation => 72 bunches (H84) with =>6 bunches (H7)

  5. Nominal PS beam for the furture LHC (4/6) The 72 bunches at PS ejection

  6. Nominal PS beam for the furture LHC (5/6) Only 1 measurement is still missing => the transverse emittances in TT2 in the presence of bunch rotation Emittance measurements using the Semfils in TT2 without bunch rotation H - plane V - plane

  7. Nominal PS beam for the furture LHC (6/6) Emittance measurements using the Semfils in TT2 with bunch rotation => Electrons are created ... H - plane

  8. Electron cloud build-up visible on electrostatic pick-ups (1/5) Nominal beam seen on the pick-up 208 in TT2 Without solenoid cf. W. Hofle With solenoid ~ 50-100 G

  9. Electron cloud build-up visible on electrostatic pick-ups (2/5) Pick-up 208 in TT2 (with and without solenoid) Pick-up 03 in the PS (in the last turns)

  10. Electron cloud build-up visible on electrostatic pick-ups (3/5) Nominal beam (but with 84 bunches) seen on the pick-up 208 in TT2 Without solenoid With solenoid ~ 50-100 G

  11. Electron cloud build-up visible on electrostatic pick-ups (4/5) Nominal beam (but with 84 bunches) seen on the pick-up 03 in the PS => No coupled-bunch instabilities...

  12. Electron cloud build-up visible on electrostatic pick-ups (5/5) Effect of a gap in the bunch train => Helpful as predicted (cf. Roberto’s pictures) Simulations by F. Zimmermann => It predicts the electron cloud build-up in both the PS and TT2 (cf. Frank’s pictures) Next studies • See if the beam becomes unstable at the end of TT2 (it does not seem to be the case according to recent SPS MDs) • Try to have a clean measurement of the transverse emittances in TT2 using the Semfils=> capture of the e-...

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