LHC%20Closed%20Orbit%20For%20Beam%202

1
LHC Closed Orbit For Beam 2
J. Wenninger December 2008
2
Closed Orbit
Sector by sector dp/p offsets

• RMS 1.6 mm H, 1.3 mm V with little effort !!!
• Vertical bare orbit converged well.
• Need to be careful when correcting orbits with
  large initial rms convergence issues to the
  non-linearities
• gtgt send in steps (20 of full correction).
• LHC fRF,cap,LHC 400'788'963 Hz
• LHC Theoretical fRF,nom-LHC 400'788734 Hz
• Average energy offset of CO -0.094 -9.4
  units.

3
Horizontal Orbit 12th Sept 08

• Corrector RMS 10 mrad with MICADO

4
Vertical Orbit 12th Sept 08

• Corrector RMS 8.6 mrad with MICADO

5
Bare Orbits

• Bare orbits after linear unfolding of all
  corrector kicks.
• Similar quality H V 12 mm rms H, 11 mm rms in
  V peaks 30 mm

6
Alignment

• The bare orbit rms is related to the misalignment
  through an optics sensitivity factor k
• RMSorbit k RMSalignment

R. Steinhagen, S. Redaelli, J. Wenninger,
CERN-AB-2005-087
An estimate for the rms alignment error is
therefore given by rms orbit/30 0.36 (V) to
0.4 (H) mm
7
Ultimate Correction - H

• Corrected orbit with SVD 240 eigenvalues (
  limit)
• H rms value dominated by dp/p offset, rms 0.52 mm
  without dp/p contribution.
• No excessive kick (but some larger kicks around
  IR6 and IR8).
• Typical max. kick _at_ 7 TeV is 80 mrad.

8
Ultimate Correction - V

• Corrected orbit with SVD 240 eigenvalues (
  limit).
• V rms value down to 0.35 mm (rejecting some more
  or less obvious outliers).
• Max offset of good (green) BPMs is -1 mm !
• The corrector settings reflect the systematic V
  offsets in S23, S34 and S45.
• No excessive kick (but some larger kicks around
  IR2).
• Typical max. kick _at_ 7 TeV is 80 mrad.

9
Conclusions

• The BPM system performance was great (at least
  for this stage).
• Orbit corrections worked well and converged
  optics reasonable.
• Bare orbits indicate good alignment of 0.35 to
  0.4 mm.
• We have to understand the funny vertical offsets
  in sectors 23, 34, and 45. Can be partly, but
  apparently not fully, explained by BPM offsets.
• We can potentially achieve a very good orbit rms
  (ltlt 1 mm) in both planes with reasonable kick
  strengths could can 1-2 sigma of aperture at
  450 GeV !