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Cooling and warm-up of the VELO under neon atmosphere

Cooling and warm-up of the VELO under neon atmosphere. conditions results (Jan 28  30) implications. Warm cool tests with the backup cooler to investigate the possibility to operate the VELO and PU-detectors, while LHCb beam pipe and VELO are under a neon atmosphere of ≈860 mbar.

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Cooling and warm-up of the VELO under neon atmosphere

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  1. Cooling and warm-up of the VELO under neon atmosphere • conditions • results (Jan 28  30) • implications VELO Nikhef

  2. Warm cool tests with the backup cooler to investigate the possibility to operate the VELO and PU-detectors, while LHCb beam pipe and VELO are under a neon atmosphere of ≈860 mbar. How do AP (=pbeam) and DP (=pbeam - pdet) behave ??? Recently temperature variations in the pit have generated variations in DP of the order of 3 mbar in 5 hours. Baseline: Vacuum PLC and active neon gas injection system (GIS) guarantee that DP stays within range, i.e. (-5,+2) mbar. However, present GIS is not designed for continuous operation. Data taken on January 30, 2008 VELO Nikhef

  3. Cooldown to 10 oC T [oC] Baseplate heating ON DP [mbar] DDP=4 mbar BPH OFF DDP=3 mbar BPH ON VELO Nikhef

  4. Warmup from 10 oC T [oC] DP [mbar] VELO Nikhef

  5. Via movement of the detector halves it is possible to manipulate DP: • @AP=860 mbar 1 mm/half corresponds to a DDP of 0.6 mbar. • However, to do this some hardware interlocks have to be temporarily • overruled. • Possible procedure: • move detectors such that DP=-3 mbar (safety margin of 2 mbar to • the lower limit of -5 mbar) • cool to 10 oC with baseplate heating ON • DP will become ≈0 mbar (safety margin of 2 mbar to the upper • limit of +2 mbar) • Without an active neon gas injection system cooling of the VELO • to 10 oC implies: • modify certain hardware interlocks • quasi-constant surveillance of DP • if needed, bypass some interlocks and adjust detector position to • bring DP back in range, i.e. (-5,+2) mbar. VELO Nikhef

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