Sheila, Ronaldas

Residual gas noise consists of squeezed film damping noise and residual gas phase noise in arms. Live pressure noise channels are used for both noise sources. In addition, gas composition is taken into account, e.g. we use X contributions (H, H2, 17amu, H2O, N2) for squeezed film damping noise. Relative gas composition are taken from Chandra's RGA scan (thanks for that!). As for phase noise, we assume that gas composition in arms is dominated by H2.

Squeezed film damping noise should be reduced by factor 2.6 for O3 due to changed design for reaction mass, see the top plot of p. 6 in LIGO-T0900582. Thanks to Peter Frischel for the reference.

First plot ('res_gas.jpg') gives total gas noise contribution.

Osem noise now includes live channel data for all osem sensors (4 test masses * 6 sensors) rather than a model. Second plot ('model_vs_channels.jpg') shows a difference of using osem model and live channels, where red steady line represents model and all other lines are channel data.

Third plot ('osem_model_vs_channels.jpg') shows a total osem noise contribution.

Fourth and fifth plots ('RGA_*.pdf') are RGA scans made by Chandra for corner and end-Y stations.

As always, any suggestions for improving noise budget are welcome.