Notes from Beam Commissioning meeting Tuesday 16th December

Presentations

Notes

Tune etc

• Ralph notes clear effect of QT hysteresis
• Discussion whether 0.06 observed coupling matches FIDEL prediction - follow up.
• PLL not tested in LHC, however tests successful in SPS.
• Discussion on Ralph's attempt to extract Q' from analysis of injected beam/circulating beam data.
• Orbit stability - commensurate with COD power supply ripple
• Spikes - are a betatron oscillation, larger in vertical plane - multiple sources in 2 & 8 - on the one LHC cycle. Check in 2009 by switching off pulsing transfer line elements with circulating beam.

Quench Analysis

Increased integration times - BLM thresholds to be re-evaluate given new number for quench energy (13 - 16 mJ/cc).

Orbit etc.

• Jorg reckons the spurious dispersion is not due to steering - dispersion free steering appears not to be effective. (A quad off by 5-10%, or a big dipole?)
• LHC bare orbit 10-12 mm in both planes, peaks up 30 mm.. Alignment looks excellent.
• Ultimate rms closed orbit - 0.52 mm H, 0.35 nm V.
• Cause of sagging vertical BPM - not clear. Temperature?
• Momentum - can we handle a floating 2-3 units? Needs to be checked under more controlled conditions.

Optics checks etc

• Orbit effect due to initial large offset in QTLI.11L8.B2 noted
• Other polarity problems noted - to be put right and checked.
• BPM noise floor around 0.2 mm. SUSSIX on individual BPM gives nice tune plots and points out faulty BPMs.
• Coupling analysis confirms 0.06 - which is apparently four times the MAD prediction.
• Yi-Peng: MQTLI.11L8.B2 off by some mm. - a mystery - to be checked.
• Note vertical dispersion at beam 2 injection point (from OD.A78 analysis).

Mike Lamont Jan 09