Summary notes of the LCU meeting on 08/10/2007

Present: IA, MA, CB. RB, HB, RC, RdM, SF, MG, WH, JJ, PL, MM, TP, TR, FR, FS, TW  +  M. Bai from BNL  and  Yiton Yan from SLAC

Follow up of Actions

• Issue with the closed orbit corrector at Q5.L8 -> WH (pdf file)
  WH presented a follow up on the question if and how we could live during commissioning with a missing orbit corrector in Q5.L8 (Beam 1, only). This orbit corrector is used to generate the crossing scheme (50% of its strength).
  The missing corrector reduces our flexibility margin to either transverse IP displacement (1 mm) or closed orbit correction at Q5.L8 (about 1 mm).
  WH found an alternative, using a modified crossing scheme including the corrector in Q7, which should work sufficiently well for the commissioning for beta* from 10 to 1 m.
  The possibility of using instead of the faulty cold corrector a warm corrector magnet (MCBCW) will be discussed with K H. Mess.
• Interleaved or non-interleaved injection -> SF
  SF will report to the LHCCWG on the 9 October on this topic.
  So far it appears that there is no strong argument for or against interleaved injections into the LHC. WH comments the observations made at LEP (impossibility of filling one beam once the other was already circulating) should not apply to the LHC. During the ppbar operations the beam-beam separation was much smaller than in the LHC and no problem was found.
  It, however, considered important to perform numerical simulations on the impact of beam-beam at injection.

Report from meetings

• ICC -> MG
  The leak in sector 4-5 on the DFBA is fixed and the cool down can continue.
  A new SSS was installed last week in sector 8-1.
  A leak in sector 5-6 was found and is being studied.
  Sector 3-4 will soon be pressure tested. It is expected that the work on remaining interconnects will all be completed this month.
  Aperture tests using a small ping-pong ball-like structure with a 40 MHz emitter in sector 7-8 were successful.
  Concerning the issue with the PIMs, it was decided to shift longitudinally the arc SSS clockwise up to Q11 by 2 mm. The new positions should be included in our MADX sequences and become the new standard values.
  Lyn Evans stated that helium supply is not an issue.
  Survey found some incorrect tilts. This will be corrected mechanically or electronically taken into account on BPMs.
• SLM -> MG
  F. Bordy will replace J.-P. Delahaye as deputy department head and J.-P. Matheys will be appointed leader of the AB/ADM group, both effective from 1st of January 2008.
  Concerning requests for fellows and students in our group, one fellow each will be requested for collimation, coupled bunch instabilities and beam-beam studies. The budget for students should allow to hire one further PhD and technical student, possibly as backup for the fellow requests.

Preliminary results and future plans for SPS MDs for the on-line model -> IA (pdf file)

IA reported about first results from recent MD studies concerning the on-line model. The BPM data was not always reliable, but still allowed to test orbit knobs and corrections on a technical level. Knob creation and correction software and multi-turn orbit acquisition were successfully tested. The upcoming TI2 tests will be used to further test the on-line model.
A detailed analysis of the measurements will be presented in a forthcoming meeting.

The new V6.501 optics -> TR (pdf file)
TR recalled that the aim of the rematch of insertions in optics V6.501 is to recover aperture in the insertions. Insertions for V6.500 were still constraint to the design report phase advances fixed five years ago. He showed a table with minimal apertures in the insertions in both V6.501 and V6.500. The cleaning insertions were left as in V6.500. IR1/5 aperture were already adequate in V6.500. The rematch of the other insertions (2, 5, 7, 8) allowed to regain a bit of aperture. The validity of the new phase advances in IR2, 8 remains to be confirmed for the collision optics. 

Linear knobs generation in MADX -> RdM (pdf file)
RdM presented methods to create linear knobs with USE_MACRO in MAD-X. He illustrated cases for the tune adjustment. The extra code could soon be incorporated with CVS in the standard MAD-X repository. JJ said that knobs generation existed also in MAD8 and is possible with the help of Mathematica.

Scraping in the SPS for LHC injection -> P. A. Letnes  (pdf file)
PL described his current work as technical student in our group. He wrote and tested a high level controls java application for the SPS scrapers. The code can be considered now to be in a "beta" stage, meaning that it is sufficiently tested and stable such that it could be used in standard operations by Joerg Wenninger et al. He also described further plans and asked for feedback and suggestions on the subject of simulations for the scraper. It appears that tracking studies, which would allow determining how much energy is lost were and how fast, would be very useful. Further suggestions and help, in particular on the simulation of the SPS aperture are welcome.

AOB
The next meeting will not be in two weeks, but likely the Friday or Monday after.

Last update: 17-October-07

MG & HB

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