• Report from meetings
  • MEB -> MG
  • A SpSSS with a MQ is under-performing and it has probably to be re-measured.
  • There was a confusion in the files reporting the geometry of the D2L107 allocated to slot IP2 left. A swap of V1 with V2 was found. Following this finding, the already allocated dipole turns out to be the best choice taking into account the special loss scenario highlighted by SF.
  • An important failure occurred in the heat exchanger pipes of one of the triplets during the pressure test of sector 7-8. The triplets were isolated and pressure tests continued successfully. This failure is possibly due to a design feature and a destructive test of a spare will be performed to reproduce the problem and find a solution. An issue occurs regarding the access to the already installed triplets which may need to be un-installed. In this respect, alignment optics should be reviewed in view of an engineering run without the triplets.
  • During a power test one dipole in sector 7-8 was found with a short-circuit. SF adds that this seems to be an isolated problem and that it can be repaired in situ.
  • SLM -> MG
  • There are still discussions for the reorganization. The new group structure will be implemented as of 1st of February 2007 and it will be effective for the next MAPS exercise.
• Phase advance scans for IR4 -> RdM, TR (pdf file)
• A problem was observed with the new matching method while used on IR4 (Jacobian for low penalty function). It is still not yet fully understood.
• However, several new features were implemented, such as
  • Use of SVD
  • Printing the rank of the Jacobian for each iteration
  • Control of the minimum singular value.
• Such an approach was used to evaluate the tunability of IR4. Using a linear step method for the target phase advances the accessible region in the space of horizontal and vertical phase advances was computed. This region is smaller than the one originally determined by A. Verdier.
• An algorithm for a random sweep of the phase advances was implemented (quite lengthy process) and a larger accessible region was found. The region is smaller on the high-side of horizontal phase advances, probably due to new aperture constraints. MG suggested to make extra runs by forcing the horizontal phase advance in the high-side.
• Replying to questions by SF and YP, RdM answered that the previous solutions are always used as initial conditions for the next matching run and the phase advance step is of 0.001 radially, with a random distribution of the angle.
• Replying a question by SF, RdM pointed out that dispersion is not matched to 0 at the IP. SF suggested to have as a target in the matching a value of around 30% of the dispersion in the arcs(50cm), which is used for the aperture tolerances.
• It is suggested to plot n1 and the dispersion vs. the horizontal and vertical phase advances to check that the aperture constraints are fulfilled and the dispersion is small enough.
  
• Status of optics database for V6.500 and polarities for V6.501 -> TR (pdf file)
• A new polarity convention for MADX is discussed.
• Previously, the sign information was in the strength file and not in the sequence file.
• The most complicated case is the powering of the triplets where power supplies are both in series and in parallel.
• An issue occurs with MQ and the adjacent MQT, which inherits the polarity from the MQ.
• There is need for feed-back from all interested parties to finalize this.
• SF favors that the strength of the magnets carry the sign as it was done for all the machines the last 10 years. He also proposes to have and additional attribute to contain the polarity information of the element.
• Questioning who is proposing the change, TR replies that it is Markus and the database group.
• MG  suggest that in the discussion, the software team and operations (Mike Lamont) should be included. A dedicated will be organized in January 2007 (Action: TR).
• DFBXs and aperture model in MADX -> TR
• Some improvements have added in TWISS
•  The apertures and tolerances can be listed (functionality added thanks to Hans Grote).
• Kmax and Imax for each element is defined in sequence file (extracted from the official database),  with calib=Kmax/Imax and Kmax as properties of elements. SF questions if Kmax is the 2nd derivative of the field. TR will check this (Action: TR).
• AOB
• Thys found that the official magnet database contained some errors. An ECR is being prepared to update the values.
  • The strength of cold D3 and D4 was not updated with the change of optics versions.
  • The option of running triplets in IR2 and IR8 at 220 T/m and 222 T/m, respectively, will be officially recorded in the ECR. It was highlighted by M. Zerlauth at al. that, due to limitations imposed by the cables, triplets in IR5 could not be ran at values higher than 205 T/m (at 7 TeV).
• A code called WISE was written by P. Hagen (AT-MCS) that gathers the magnetic data as well the geometry ones and produces a MADX input representing the machine as built. It is stable and complete.
• Thys has worked on the magnetic and geometric part and further cross-checks need to be done per magnet.
• For the MBs some features are corrected by SF, but not serious bugs found.
• For the triplets a lot of issues were found (wrong assignments of magnets, wrong direction).
• for the other classes of magnets the cross-check is in progress (Action: MG, YP).

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