LIGO Document T040001-v1

Vacuum Hydrocarbon Outgassing Requirements

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Document type:
T - Technical notes
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12 Jan 2004, 00:00
There are two basic reasons to limit the outgassing of materials and assemblies placed into the LIGO vacuum system:
to limit the phase noise associated with scattering from the residual gas species in the long Fabry-Perot arms, and
to limit mirror optical loss (scattering and absorption) due to condensed vacuum gas species.
The phase noise requirement must be satisfied by ensuring that the integrated outgassing from all of the LIGO in-vacuum components is within the pumping capacity of the system to keep the partial pressures of each gas species below requirements. A set of "goal" and "initial LIGO requirement" partial pressures, as a function of atomic mass number (AMU), has been established. In this memorandum, a proposal is made for a set of "advanced LIGO required" partial pressures and an associated budget per subsystem. The required background outgassing rate in the vacuum bake ovens used for residual gas assay (RGA, or mass spectrometry) is also discussed.
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Notes and Changes:
the -v1 memo is the same as -x0
The spreadsheet was slightly updated, quite some time ago.
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