Summary notes of the LCU meeting on 09/07/2013

Present: RA, FB, HB, OD, SF, MHF, MG, JJ, AL, ASL, KK, EM, BR, GR, MS, RT, RV ZF

Report from meetings

• SLM and general information -> MG
  Massimo reported about non-conformities, which became apparent in LS1 and which should be analyzed by us: RF-fingers right of IP5 in the Q1-Q2 region, and a faulty MQT. We should also follow up on actual triplet strength limits and requirements at 6.4 - 6.5 TeV and see if we could to without pre-squeeze in IR2/8.
• MAD-X status
  Ghislain said he is in the progress to review the MAD-X documentation, which is now based on LaTeX and that he expects to have a proper latex version later in summer. Helmut said that he committed the makethin code for the recently proposed upgrade as discussed on the 19/04, including dipedge generation with documentation written in LaTeX . For the moment, the dipedge generation for bends is not yet on by default, for backward compatibility during the current tracking campaign. Later it will be on by default.
• LHCC, LBS -> HB
  Helmut reported about discussions on forward detectors (roman pots, movable pipes) and their possible use in standard physics. He already gave a short summary in the last LMC meeting on this subject.  The last LBS meeting had presentations on background observations at high beta* and a comparison of 25 and 50ns, see indico.

Thick quadrupole tracking module in MAD-X -> AL

Andrea Latina reported on the development of a thick quadrupole tracking module in MAD-X. Sympletic transformations for thick quadrupole tracking are known and thick quadruple tracking already existed in MAD-8. He presented the expressions that he uses and checked the off-momentum behaviour. The presentation triggered a discussion on the merits and consistency of the variable choices and equations. This should be further followed up and clarified between our optics and tacking experts, with the aim to arrive at a set of generally accepted reference equations.

IP Aperture LS2-LS3 -> FB (slides)

Frederic presented recent work done for the HL-LHC in the framework of the work package 8 on collider-experiments interface in close collaboration with several other work packages (optics, machine protection, collimation…).

One key point studied is the implications of the increase of the TAS aperture from currently 34 mm to about 60 mm planned for the HL-LHC in terms of experimental conditions (protection, background..), combined with a reduction of the central beam pipe radius.
He showed examples of tracking with the current and future aperture, see the slides. The central beam pipes will be more exposed to beam losses and in particular off-momentum particles. He started detailed simulations using SIXTRACK with a simulation of crab cavity failures, performed together with Bruce Rendon. 

Missing MQTs and including dipole b2 errors in the design model -> ASL (slides)

Andy Langner analyzed the effect of including b2 errors in the baseline model as proposed in the last meeting and into consequences of a missing MQT. The inclusion of our best knowledge of b2 errors in the model will result in reduced corrections and better convergence and precision of our measurement/corrections procedures. 

Correction tables may be required at intermediate energies. This will be followed up by Massimo and Ezio.

Andy also looked at the consequences of the recently observed non-conformity, a possible faulty MQT 18.l1. The option of removing this single magnet from the circuit of four magnets does not seem ideal. Therefore, unless the non-conformity can be fixed, it will be better to not use this circuit.

Stephane asked to also check the effects for the ATS optics.

Issue with RSS circuit -> RT, YL (slides)

Rogelio reported about studies on the requirements for skew sextupoles which he did together with Yngve, required mainly for the corrections of the a3 component of the main dipoles. A very good agreement between the model and measurements was observed. The corrections required are quite small, for 7 TeV, a maximum of 14.5% of the available strength is expected, and that 20% appears to be a safe upper limit. Stephane also asked to verify this for the ATS optics.

AOB 

None

Last update: 12-July-2013

MG & HB

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