LIGO Document E1400310-v2

aLIGO Availability Estimate

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Document type:
E - Engineering documents
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17 Nov 2014, 16:54
This is a revised analysis of the availability (up-time) of the aLIGO system.
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Notes and Changes:
section 5.5:
- added verbal justification for longer weekly maintenance period than for i/eLIGO
- added verbal justification for some allocation for facility maintenance hit

section 6.1:
- revised the availability numerical estimate
- added an estimate of dual coincidence up-time based on scheduled simultaneous maintenance periods
- revised the plots and table

section 6.2:
- added more detail of L1 and H1 power interruption data
- noted lower power interruption rate more recently at LLO
- noted decision to drop consideration of a UPS system for now
- revised the hardware failure table; in particular the DAQ failure rate (derived from the Sparing Analysis was unrealistically high)
- added a facility maintenance event to the table
- added explanatory text on how the failures requiring prompt attention are treated differently than deferred repairs (which occur during maintenance event periods)
- Added note that repair of non-trivial hardware failures can only occur (more or less) immediately if they occur during normal work hours. If a non-trivial hardware failure occurs during the owl shift or a weekend, it will necessarily take considerably longer to repair, since it will require expert science or engineering staff to make the repair/replacement. This has not yet been factored into the analysis. This will increase somewhat the 3.48% estimate for repair time for failures requiring prompt attention.

section 6.9: added notes on Facility failure/repair considerations

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