Summary notes of the LCU meeting on 19/05/2009

Present: MA, RA, OB, AE, WH, BH, JJ, EL, YL, JN, FR, FS, YS, SW, DW, FZ

Report from meetings

• SLM -> MG (slides)
  MG reminds us that Olav Berrig is now in charge of the LHC optics "database" helped by TR on a voluntary basis.
  MG also reminds us about the course on "habilitation electrique", which is required for access to the tunnel and which can be followed on the web.
  There was a request for volunteers to help with the patrols in the tunnel. These patrols are expected to start on the 20th of June.
  We have been asked to provide feedback on the strategy for CERN publications and the categories needed like departmental and project reports. JJ suggested to keep it simple and to minimize the number of different reports and notes.
  We got results from a simulation of the CMS stray field from S. Russenschuck and B. Auchmann. The data is available as two-dimensional mesh as a function of s and r. YS will follow up with FS on the implementation of solenoids in SIXTRACK.
  There has also been follow up on the y-chamber for ALICE. J. Uythoven and R. Appleby will prepare a note to report about the outcome of the study. Such a note should be used to support the final decision concerning modification of the chamber (if required).
  MG showed slides and discussed non-conformities that have been observed in the LHC. In particular, there have been observations of rf-fingers which stick by up to 2 mm into the aperture. It is believed that they were not due to the warm up but already there from the installation.
• LPC -> HB (slides)
  HB reported from the first LPC meeting this year, see the slides. Of particular relevance to us was the last presentation in that meeting given by Massimiliano Ferro-Luzzi on "Run scenario and plans to increase intensity and luminosity in 2009-2010". The presentation includes a table with LHC running parameters. As follow up it is planned to update the EDMS document on run parameters. In the following discussion we agreed that it is important to commission the LHC step by step and to avoid to change several crucial parameters at the same time. The beta*=3 m given with crossing angle is conservative as justified for luminosity expectations.
  The aim for the first year of LHC operation is also to learn about possible limitations and to try to operate with crossing angle down to beta*=1 m.

Recent optics studies for improving aperture at injection in IR2/8  -> MA (slides)

MA performed optics studies for IR2/IR8 at injection. Two approaches have been presented:
- The crossing scheme was optimized: an angle was introduced in the parallel separation, thus reducing the peak in the bump shape. Furthermore, the IP is shifted transversally (as already proposed by SF for IP1/5 in collision and JJ and TR for IP2/8 at injection). The overall gain is about 0.4-0.5 sigma for n1.
- the increase in beta* (from 10 m to 11 m) for IP2 and IP8 provides an additional gain of about 0.5 sigma in aperture. This implies a few per cent changes in betas and phases as relevant for injection with consequences for the transfer lines which remain to be checked by TE/ABT (the feedback is awaited by end of June).

RA said that a lot of work is required to follow up on optics changes with simulations for collimation and that he would prefer that we freeze the LHC optics. MG replies that the new optic settings will be stored in an appropriate directory of the optics database to avoid perturbing the on-going studies. He also comments that it should be possible to find a quick way of assessing the impact of small changes, which go in the positive direction (as they increase the aperture).

AOB

None

Last update: 19-May-09

MG & HB

Back to LCU Minutes