Summary notes of the LCU meeting on 02/06/2009

Present: MA, OB, CB, HB, AE, SF, MG, WH, BH, JJ. EL, YL, JN, FR, AR, FS, YS, SW, DW, FZ

Report from meetings

• SLM -> MG (slides)
  The "habilitation electrique" mentioned also in previous meetings also requires a practical exercise, which should be better defined. For those who still have to do this the recommendation is to put this on hold until this has been clarified.
  A general ABP group meeting is planned for the 2nd of July - likely later in the morning. It will have a more general part and very short presentations by the section leaders.
  We will have a student advisor in ABP to help with general and administrative matters for all technical, PhD and summer students. BH has been asked to do this.
  There has been a follow up and clarification on the subject of the beam1/beam2 current swap at MQTL7.R3 observed in the LHC with beam and affecting the optics via a large beta-beating.
  Brennan Goddard and Malika Meddahi have been asked to check the consequences for injection of the changes proposed by MA to improve aperture in the LHC at injection in IR2/8, as shown in our last meeting. Files for the new IR2/8 option have been made available in an extra subdirectory for tests.
  There has been a discussion on the details of the aperture of the LHC at the experiments in the LEB, chaired by Raymond Veness. While this "experiments beam pipe" working group aims at upgrades with smaller beam-pipes, it has also become clear, that our aperture model for the current experimental beam pipes should be improved and that there is some concerning about the aperture for the CMS vacuum pipe (high-beta optics). MG will follow up on this.
  FS said that IT will help with BOINC. One issue to follow up is the linux upgrade to SLC5. Working on the GRID is also considered.
  MG showed the measured horizontal misalignment in LSS4 before and after alignment. Few points are still significantly off-axis and further follow up required.
• LHC Beam commissioning WG -> HB (slides)
  HB showed the slides he prepared for todays LHC beam commissioning WG on "Putting the beams into collision" with comments from the last LHC background study group meeting. The procedures and documents for collisions in beam commissioning STAGE A remain valid. Some details of STAGE B like the exact values for the crossing angles for the various proposed beta* values (1, 2, 3 m) at 5 TeV should be agreed and documented (follow up organized by MG). HB also said that extra button pickups have been installed close to Q1 in IR1&5 as requested by the high beta* experiments ALFA and TOTEM. They could also be useful to measure with improved precisions the residual beam separation in early LHC operation with few bunches and no crossing angle. FS asked that any new pickups and other new equipment should always be defined in the MAD-X sequences. The choice of the element class name for new equipment in MAD-X sequences is not obvious and requires follow up.
  MG asked WH about the quantitative criterion to be used to define the crossing angle and the parallel separation bump for the special configurations to be used in the physics conditions for the next run. WH replies that the separation at the parasitic encounters with a crossing angle should nowhere drop below 10 sigma and the parallel separation should aim at 12 - 14 sigma. This is better than nominal and should be safe.

Optics design studies for a LINAC/ERL-based LHeC -> AE (slides)

FZ shortly introduced the work. After having already been with us as a summer student, AE started in February to work at CERN on the linac option of the LHeC supervised by FZ.
He started first to work out the main parameters using Mathematica, then used PLACET and more recently MAD-X as described in the presentation. A geometry with a racetrack and 2 recirculation's is believed to be most effective. The optics will have to work for a large energy range and it is not easy to calculate and optimize chromatic corrections with the available tools. FZ said that Georg Hoffstaetter suggested to lower the injection energy to get the highest energy recovering efficiency. There were doubts on MAD-X with synchrotron radiation and it was suggested to check with MAD8, SIXTRACK or possible PTC and on the proof of principle of ERLs relevant for this application. After the meeting FS confirmed that radiation effects are indeed implemented in MAD-X (thintrack module) as well as in PTC (ptc_track module).

AOB

None

Last update: 03-June-09

MG & HB

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