camilla.compton@LIGO.ORG - posted 16:08, Friday 17 November 2023 - last comment - 21:20, Friday 17 November 2023(74262)
New MICH FF Filter in Use
Gabriele, Camilla
After the LSC FF measurments taken on 15 Nov 74220, Gabriele refit the MICH FF. It's now being used, was loaded into FM7, saved in sdf and ISC_LOCK.
This reduces the Q of the 17.7Hz feature from ~300 to 90, allowing Louis to reduce the amplitude of KAPPA_TST 74259. We may still think about reducing this 17.7Hz feature more or notching it out of MICH.
MICH comparism plot (pink = new) and Gabriele's DARM-MICH coherence plot (Orange = new) is attached. The new MICH FF is overall better but is a little worse around 30Hz and 60Hz. It's been harder to fit over all frequencies since we swapped to using the ETMY PUM for FF.
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I'm attaching a quick and dirty comparison of DARM zoomed in near the L3 SUS line at 17.6 Hz. The thin red line is DARM from October 9th, before the MICH FF swap on 10/12 (LHO:73420). The grey line is from yesterday, showing the of the filter installed on 10/12. The yellow trace is from earlier today after the new filter was installed. Certainly the current filter seems to be better and the peak it produces is both farther from the 17.6 Hz line and lower in amplitude than the filter that has been installed the last few weeks. Still, I was not able to completely undo the L3 SUS line amplitude changes from LHO:74145 and maintain TF uncertainty < 0.5% (amplitude reduced earlier today in LHO:74259).
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