Summary notes of the LCU meeting on 24/06/2010

Present: HB, RDM, SF, MF, MG, SH, BH, EL, DW, FZ

Report from meetings

• General information -> MG
  Training for electrical awareness is done on the web. People who did this should be automatically receive a warning when it is time to update the training. Still everybody is encouraged to check himself using EDH if he is up-to-date on safety courses, to avoid to loose the access permit.
  There is a department retreat today with a discussion on manpower planning including fellow and LD-IC contract strategy.
  There has been pressure in the last Council week from CERN member states to reduce budgets. New projects are on hold.
  We have a new member, Steffen Hillebrand who will work with RA on Laser/plasma acceleration.
  LHC commissioning is going to operation with nominal bunch intensity and then an increase in the number of bunches. The aim for the summer is to operate with 24 + 24 bunches, beta* = 3.5 meter. Triggered by a request from LHCf, 100 murad crossing angles were introduced for IP1&5.
  The memorandum of understanding for BOINC is being finalized.
• LBS -> HB
  We had the LBS#15 meeting on the 14 June. Information is on indico. A report from the LBS was presented in the LMC#60 on the 16 June.

Recent results for field quality of new magnets for LHC upgrade -> BH (slides)

BH presented simulation results for the recent LHC upgrade optics.
He determined the dynamic aperture (DA) using SIXTRACK for 1.e5 turns.

This was used to derive specifications for the tolerable multipole components for the new D1 magnets and larger aperture triplet quadrupoles.

For the new triplets is it envisaged to have low-order correctors for a2, b3, a3, b4, a4, and b6. Tracking studies were performed to determine the tolerances on remaining multipoles. The impact of non-optimal settings of the corrector coils as well as the impact of feed-down from crossing angle was considered.
The specifications are described in two SLHC publications.
For the D1 is already confirmed that the requested field quality can be achieved with an appropriate magnet design.

One the other hand, discussions to establish the feasibility of the field quality for the new triplet quadrupoles should be launched with experts.
HB asked if there are plans to check the requirements for dynamic aperture in the actual LHC. Indeed it would be important to test the assumption that a factor of two between simulations and reality should be assumed. This is based on HERA experience and should be tested on the LHC. Many points were raised during the ensuing discussion such how to devise a reliable method to measure DA. Also, the current strategy for the beam commissioning does not seem to leave much time for these topics.

Recent results of beam-beam simulations for LHC upgrade -> EL (slides)

EL showed beam-beam simulation studies which complement the single beam DA studies for the LHC upgrade. Turning on beam-beam in simulations typically reduces the DA from 14-16 down to around 7.5 sigma. The beam-beam studies were done simulating 1.e6 turns in the LHC. The simulations were also performed using the latest upgrade error tables and beta* down to 30 cm. A beta* of 40 cm would allow for larger crossing angles and larger DA from beam-beam. These simulations were all done for round beams. For the future it is planned to extend the beam-beam simulation to flatter, elliptic beam cross sections.

Following a number of recent discussions among some of the trackers, MG reminds that SixTrack always lumps thin elements, for example thin multipoles. This is not the case of MAD-X. Hence, a difference in the number of assigned errors between MAD-X and SixTrack might not be a source of concern.

AOB

None

Last update: 03-July-10

MG & HB

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