Summary notes of the LCU meeting on 8/03/2011

Present: CA, RB, HB, RC, RDM, MG, YL, TM, RM, MS, RT, GV, RS

Report from meetings

• SLM and general information -> MG
  The SLM discussed the medium term planning and follow up of Chamonix'11. As now generally known, the LHC will run in 2012 followed by an 18 month shutdown.
  The work in this section will be more focused towards the HL-LHC upgrade.
  The last LMC had a report by Dominique Missiaen on the recent IR alignment. The alignment of the triplets in pint 5 was particularly difficult. During the last step of the foreseen adjustment, as large movement was observed and required investigations. This seems to be due to the additional mechanical constraints due to the repairing action taken to mitigate the impact of the incident occurred in the past.
  Work is in progress and followed up in the framework of the LEB on the reduction of the experimental beam-pipes, which has now already been requested for the first long shutdown in 2013. The reduction from 58 mm (ID) to 45 mm (OD) diameter should be ok for the normal optics but may limit the high-beta TOTEM/ATLAS-ALFA performance.
  BH joined the team of LHC coordinators. LHC MDs will be coordinated by RA and FZ. A web page was set up, the link is here.
  LHCb is now also interested to participate in the medium energy run early this year. MG was asked by the LPC co-ordinator to evaluate the VELO aperture for the medium energy run.
• LBS -> HB
  The last LBS-meeting had a discussion of the plans and requirements for 2011. One priority is beam-gas simulation studies. For more details, see the LBS presentations and minutes on indico. HB said that he recently discussed with the technical coordinators of ATLAS and CMS about the possibility to join the LBS activities into the planned machine detector interface activity for the HL-LHC.

Continuous Beta-Beat Measurement at the LHC - Status and Prospects for 2011 -> R. Steinhagen (slides)
In Ralph Steinhagen reported from work by him and Marek Gasior on a the possibility of a continuous beta-beat measurement, see the slides. He uses the very sensitive Base Band Tune (BBQ) detector which can detect sub-micrometer oscillations with very low noise. RS recalled and compared the sensitive of several methods to measure beta functions. He also reported from first results on a continuous beta-beat measurement using specially equipped BPMs in IR7. The beams were excited with oscillations of less than one micrometer amplitude which do not cause any significant emittance blow-up.
Ralph asked if we are interested in a continuous monitoring. We are clearly generally interested, for example to observe the b2 decay following the squeeze. In particular, given that the changes to be implemented in an upgraded BPM system are minor (cost-wise) with respect of the upgrade itself, we consider that this option should become the default for any BPM system improvement.

RT said this would be very useful if it could be set up as a generally available tool. He proposes also to have a joint measurement session of continuous beta-beating when the static beta-beating is measured and corrected.

Recent beta-beating measurements -> GV (slides)
The beta-beat has been measured in the LHC set up with beam this year, down to a beta* of 1.5 metre.

It was corrected from initially 40-50% down to the 10% level. Correction were done using many individually powered quadrupoles. It was decided not to correct globally the machine at top energy, but to perform it only at the end of the squeeze.
This method was also applied to measure and correct coupling. The correction required for IP5 decreased, which is attributed to an improved triplet alignment with the readuction of quadrupole roll angles.
Beta* values were measured. K-modulation will be used to further increase the measurement accuracy.

AOB

None

Last update: 9-March-2011

MG & HB

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