Summary notes of the LCU meeting on 28/07/2009

Present:  MA, OEB, CB, SF, MG, WH, EL, YL, AR, FS, DW, SW, FZ, C. Bat, H. Maury Cuna

Report from meetings

• SLM and general information -> MG
  MG informed that there has been a request from the VIP and protocol office that the staff fills the out-of-office message. WH and FZ asks whether it is needed to do so in case the staff is regularly reading mails even when not at CERN. MG replies that it does not seem needed, but will ask OB for a confirmation
  MG reported about a discussion on the as-built sequence with the layout database people. The current as-designed sequence reflects the situation of installed hardware on September 2008. Hence, it cannot be considered as a real as-designed sequence (e.g. some of the collimators are missing). the database people highlighted that in additional to electrical non-conformities there are also geometrical non-conformities (e.g., longitudinal shift of the SSS to cope with the PIMM issues, longitudinal position of the triplets). In case these non-conformities are included in the layout database for the as-built machine, then special care should be taken to avoid double accounting of these effects (e.g., the SU database should be adapted to this choice). MG comments that no decision was taken for this point and asked for feedback.
  LMC -> FZ
  FZ reviewed the highlights of the LMC meetings since last LCU meeting:
  - The value of the RRR is a crucial parameter for the definition of the critical resistance of the splices. The measured value is much smaller than the one normally assumed in computations: the measured value will become the nominal one for all computations.
  - Hardware commissioning of sector 2-3 progressed well (before the He leaks in the DFB) with the completion of the phase 1 and starting of phase 2 powering activities.
  - For safety reasons a staged opening of the safety valves is under consideration.
  - The nQPS was successfully tested.
  - The warm up of sector 4-5 was decided to re-measure the splice resistance at 300 K after the 80 K measurements.
  - He leaks appeared in sector 8-1 and 2-3. They are in a flexible hose in the DFBs. It turned out that the flexible hose is operated at non-nominal conditions. A detailed analysis showed that similar conditions occurs also in other sectors. In one case, signs of degradation were observed and the hose will be replaced.
  - The beam commissioning will start by mid-November and there will be no run other the Christmas break.

Final update on CMS solenoid stray field -> YS (slides)

YS briefly presented the programming work required to introduce the thin solenoid and the fringe field (derived by FZ) in MAD-X to SixTrack convertor, and SixTrack code, proper. As a follow-up of the last presentation, YS reported about the coupling effect at injection on modeling of the measured CMS solenoid stray field. Even at injection the linear coupling is negligible. The dynamic aperture computed with four additional solenoids on each side of IP5 does not show any sign of degradation.  SF comments that, as the field quality of the triplet can be critical at the level of a fraction of a unit, i.e. a fraction of a Gauss, the conclusion that the field is linear (see previous presentation) should be verified carefully. FZ comments that the modeling of the solenoid and the surrounds might not be accurate at this level. YS will have a more detailed look at the numerical data of the magnetic field.

Update on e-cloud simulations for LHC and its upgrade -> Humberto Maury Cuna (slides)

FZ introduces once more Humberto who was already with us. Humberto will work for a PhD thesis under the supervision of FZ at CERN and with a grant from EUCARD and his local institution. The current work focuses on the computation of the heat load induced by e-cloud in the LHC including some upgrade scenarios. LPA with flat bunches (with and without satellite bunches for LHCb) with a scan on the bunch intensity. A scan of the bunch spacing is also considered, including also a Gaussian longitudinal profile case.
For the LPA case, the heat load increases monotonically with bunch intensity without satellite bunches. It increases as well with increasing secondary emission yield (SEY). In the case with satellite bunches, the heat load features a minimum vs. bunch intensity. Of course, such a minimum moves with the value of the SEY.
A monotonic decrease of the heat load with bunch spacing is observed for various bunch intensities.
The Gaussian bunch case seems to provide higher heat load than the flat one.
Future studies include the analysis of pressure rise and experiments (PS and SPS).

AOB

FS announces that the latest release of MAD-X is now available.

MG announces that the LCU meeting of August 11 is cancelled and the next one will be on August 25.

Last update: 29-July-09

MG & HB

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