Summary notes of the LCU meeting on 23/10/2009

Present:  MA, HB, OD, MG, WH, BH, JJ, EL, YL, FS, MS, YS, GV, SW, FZ

Report from meetings

• General information -> MG
  The layout database and in consequence the as-designed LHC sequence are not quite up to date with the actual LHC. In particular, some collimators are missing as the as-designed sequence was based on the 2008-09 sequence, which is missing all devices installed during last shutdown. A preliminary working version for tests, optics V6.503a exists, and should be more complete for collimators as required for background studies. This version of the sequence should be used until further notice.
  It is also stressed that the layoutapertures.madx file (containing the vacuum markers) is periodically updated in the optics database, whenever corrections and additions are applied in the layout database. The sample file in the directory provides the up-to-date list of elements whose lengths have to be set to zero to avoid negative length drift. FS will improve error messages in MAD-X to help to localize and fix problems with negative drift length as suggested by TR. 
• LMC->FZ
  FZ reported about three LMC meetings. In spite of many smaller issues, the preparations for the LHC proceed rather well. An injection test into the LHC is planned to start later today and to continue through the weekend. Most sectors will first only be commissioned up to 2kA which will limit the beam energy to just above 1 TeV for this year. The commissioning to 6 kA will be completed early in 2010.
• LBS->HB
  HB reported from the 8th LBS meeting which took place yesterday. The results of the tests with signal exchange with the experiments and luminosity scan tests were reported.
  The status and first preliminary results for background simulations at 3.5 TeV were presented and first plans for background studies with beams in the LHC discussed. The next LBS is scheduled for the 26 November and include a discussion of the knowledge of the IP position and angles as requested by various experiments.

Recent optics studies for IR8 -> EL (slides)

EL presented the status of optics studies related to the squeeze for IP8 down to beta* of 2 m. The squeeze at 7 TeV will be preceded by a pre-squeeze, used to reduce the triplets' strength. The aperture at 7 TeV is sufficient with separation and crossing angle for both spectrometer polarities.

The squeeze at 3.5 TeV will be performed starting directly from the injection optics without pre-squeeze. The aperture only allows for one spectrometer polarity and beta* may be limited to 3 m. Detailed computations should be performed to verify the minimum value of beta* compatible with relaxed collimators' settings (i.e. n1=10.5) with and without external crossing angle. Beta beating during the squeeze remains to be checked. All this will be reported in the next LCU meeting.

Recent optics studies for IR2 -> JJ (slides)

JJ presented a similar study for IP2. The injection optics has extra phase advance constraints and it is hard to find a continuous transition to the physics optics. A new solution for beam1 was found, but may require further smoothing and checks. This will be followed-up at next LCU meeting.

Progress on the PTC standalone model of the LHC -> FS (slides)

Etienne Forest was recently at CERN and worked with FS on PTC. There has been significant progress on optics modeling and in particular on the standalone PTC model for the LHC. The aim is to get a full 3D placement of the two LHC rings including the TI2 and TI8 transfer lines.
Aperture is considered including shifts and data from measurements. The magnetic errors can be assigned to the thick elements.
PTC also offers a toolkit for re-splitting of elements and allow to get Twiss parameters in elements as relevant for synchrotron radiation, beam-beam and space-charge. Examples have been prepared.

Online model applications: coupling correction and aperture studies -> CAP (slides)

Carmen showed applications of the MAD-X online model. These studies and development is carried out in closed collaboration with OP (G. Müller and S. Redaelli)
One application is knobs for the machine coupling correction (largest effect expected from the systematic a2 of the LHC dipoles).
Another application is aperture studies including injection and transfer lines.
The next steps are the inclusion of non-linear magnetic errors to thick elements using the technique presented by FeRo in the past.

AOB

None

Last update: 23-October-09

MG & HB

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