Summary notes of the LCU meeting on 24/09/2007

Present: IA, RB, HB, RdM, UD, SF, MG, JJ, MM, TR, FR, FS, RT, FZ

Report from meetings

• ICC -> MG
  A Helium leak in sector 4-5 was localised in the DFBA on the IP5 side. The origin is a faulty metallic flexible. As a similar problem occurred also on the IP4 side, more close verifications are in progress to see if there is any general issue.
  Concerning the PIMs, problems were only found on quadrupole-dipole interconnects and not between dipoles. The possibility of shifting systematically the arc quadrupoles by up to 2-3 mm has been discussed in this context. According to Thys and Stephane, this should be tolerable for the optics and, in any case, it could be compensated with a re-matching. Of course, in case this option is retained a new LHC sequence should be prepared.
  There will be no TI8 tests with beam this year to avoid interference with the planned Q17.R8 exchange.
  TI2 tests will start soon.
  Pieces of paper were found in flushing tests for sector 8-1.
  A short in Q22.L8 might prevent using the MCD circuit in sector 7-8. A non-conformity concerning a closed orbit corrector in Q5.L8 was found and closed without contacting beam specialists. An LTC follow-up is foreseen in order to make it clear that any non-conformities with possible consequences on beams have to be discussed with AB (in general and ABP for optics) before assuming they can be tolerated.
• SLM -> MG
  The quotas for the conversion of LD to IC contracts (Cat. 2 and Cat. 3 staff) will not depend on the Departments, but were fixed on a CERN-wide basis.

The LHC complex in PTC -> Etienne Forest
Etienne Forest described his work with FS on the use of PTC with application to the LHC. He started to write the Polymorphic Tracking Code in the year 2000 and has been in close contact with our group. PTC uses its own, rather direct implementation of geometry which avoids complications like the bv flag in MAD-X, and allows for a rather straight forward connection of transfer lines and rings.
During this visit the complete model of the two rings together with the two transfer lines was set up. With the technique implemented in PTC it should be easier to define cryostats and introduce misalignments for cryostats.
Furthermore, it is planned to have the option of generating thin lens models taking into account the details of the original thick lens ring, so to overcome some of the design limitation of the makethin command.

Relevance of the LHC 2-Beam PTC description for the on-line model -> FS (pdf file)
FS then described the relevance of the work with Etienne for the LHC.
He recalled some of the historical reasons for the choice of mixing code in C and FORTRAN in MAD-X. PTC can be run as an add-on to MAD-X and extends the functionality of MAD-X.
Converting LHC input for PTC was rather tricky but also provided checks on Beam 1/2 consistency.
PTC has extra features and superior tracking compared to MAD-X. It allows for a fully object oriented description of the LHC. PTC tracking allows for errors, misalignment, and aperture along magnets with offsets. Much of this is already working and FS is confident that it will all be ready for the LHC startup. MG commented that a clear implementation strategy should be proposed in the coming days.

Analysis of tools for MADX on-line model -> IA (pdf file)
IA reported about recent developments and plans for the MAD-X on-line model.
As an example, he showed, how a script can be used to produce an orbit bump and to create a knob for this. He showed the detailed tables for the steps in LHC commissioning and discussed the possible use of the on-line model in these steps.
It was requested to allow for feed back of results from measurements into the model. IA said they are working on a strategy for fitting the optics model to the actual LHC.
Tests of the on-line model on the SPS are scheduled for this week during a dedicated MD period. First results will be reported in the next meeting. MG strongly encourages to pursue the experimental activity using parasitic beam time as well as to take part to the TI2 commissioning.

AOB
SF said he has been in contact with Roger on the subject of interleaved filling schemes for the LHC. So far, there have not been strong arguments for the need of interleaved filling. We are encouraged to think about this and send any comments to Stephane on this subject before the next meeting in two weeks. Even if the discussion is currently mostly focused on proton injection, it would also be useful to see if the same conclusions can be applied to heavy ion injection.

Last update: 24-September-07

MG & HB

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