Summary notes of the LCU meeting on 20/05/2008

Present: IA, MA, RB, HB, RB, RC, MG, PL, AM, JN, TR, FS, RT, SW, SY, FZ

Report from meetings

• ICC -> MG
  The LHC cool down and hardware checkout progress well. The average time for the cool down of a sector is about 6 weeks, rather similar for all sectors.
  Sector 5-6 is fully commissioned to 5.5 TeV and dipole powering is currently pushed further to 7 TeV. This will also improve our knowledge of how many training quenches will be needed to commission all of the LHC for the full design energy.
  One issue, already well known from LEP times, is the high level of humidity in sector 3-4 close to the Jura with danger for corrosion and short circuits.
  The option of doing temporarily betatron collimation in IR3 rather then IR7 until the issue of possible radiation damage of electronics is minimized will be discussed in the next LCU meeting.
• SLM -> MG
  No meeting; there was the general group meeting.

Powering requirements for the insertion magnets ->  MG (pdf)

MG showed and discussed the slides he prepared for the LTC tomorrow. Recent hardware tests revealed limitations in D3/D4 powering. MG reviewed the history of maximum strength requirements for the magnets through optics versions and possible solutions for the few cases in which limits could be exceeded (data provided by Thys). For the D4 in IR4, the DCCT limit is 6000 A and the power convertor limit 8000 A. Nominal powering (computed with measured transfer function) is beyond the capabilities of the DCCT. Replacing the DCCT with another one rated 7000 A is an easy intervention, provided an ECR is prepared to document this request. A detailed verification of the hardware limits in the D4 circuits will have to be carried out by MPP. In any case, for the 2008 run at 5 TeV, no hardware change is required.

The triplets in IR2/8 require higher powering than nominal due to the many injection constraints. The optimal value of the gradient is 222 T/m (currently for IR8 and proposed by Thys also in IR2 to improve and aperture bottleneck in Q6). The transition from the higher-than-nominal setting could be made from the end of injection up to about 6.5 TeV: this will be done at constant beta* and would avoid any issue of powering limit. In any case, for the 2008 run at 5 TeV no hardware changes are required and the change of optics could be done on the flat top. MDs could be dedicated to mastering the change of optics during the ramp.

AOB
MG reported about LHC instruments commissioning. There was a first meeting with the commissioners about organisation and responsibilities in mini-teams. This will be followed this Thursday by a larger meeting covering all instruments. An instruments hardware commissioning web-page was set up.  Several of us have been assigned to take responsibility for instruments commissioning.

Last update: 23-May-08

MG & HB

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