Cooling and warm-up of the VELO
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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

  • conditions

  • results (Jan 28  30)

  • implications

VELO Nikhef


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


Cooldown to 10 oC

T

[oC]

Baseplate heating ON

DP

[mbar]

DDP=4 mbar

BPH OFF

DDP=3 mbar

BPH ON

VELO Nikhef


Warmup from 10 oC

T

[oC]

DP

[mbar]

VELO Nikhef


  • 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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