sheila.dwyer@LIGO.ORG - posted 14:44, Monday 15 April 2024 - last comment - 10:12, Friday 19 April 2024(77182)
signals to consider for damping triple bounce modes
Jeff K, Sheila D
We are interested in which signals we can use to try to damp triple bounce and roll modes, since these are probably responsible for some of the peaks in our forest of peaks around 25-35Hz (77109 and 76505). Jeff is preparing to implement a damping path on the HSTSs so that we can try to damp these.
We looked at signals (in addition to DARM) that we may want as options for damping.
- 27.42 Hz - REFL A 9I PIT
- 27.5 Hz -nothing other than DARM
- 27.6 Hz - REFL A 45I yaw (plus several LSC signals, PRCL, SRCL, REFL45 I, POP9Q)
- 27.72 Hz nothing but DARM
- 28.2 Hz PRCL, LSC REFL45 I, ASC REFL A 9I pit, ASC REFL A 45 I yaw
Dtt template is at /ligo/home/sheila.dwyer/SUS/HSTS_damping_signals_checks.xml
Images attached to this report
Comments related to this report
"Yes and..."
Here're some plots that demonstrate the coupling between these modes and ISC channels
- at higher resolution,
- separated into ASC and LSC signals, and
- with the individual optics called out as per their ID in LHO:49643
In addition to the region that Sheila focuses on, 27 Hz and 28.5 Hz to isolate the highest vertical modes of the recycling cavity HSTS and HLTSs,
I also show the 40-42 Hz region to show the highest roll modes of the recycling cavity HSTSs.
(Note, I looked around ~45 Hz for the highest HLTS vertical modes, but they did not appear in DARM, nor any of these other sensors.)
This should help us pick the error signals, and/or how much damping we should expect to get, if we don't want to use DARM_CTRL as our error signal (due to concerns about parasitic loops, or needed to account for it inn the DARM calibration, etc.).
Images attached to this comment
Apologies. In my haste to produce the plots, I didn't read all the elements in the table of SUS resonances reported in LHO:49643, and incorrectly assumed that the table was sorted by frequency, picking off the first listed suspension that was close. Thus, in the first two attachments, - 2024-04-15_HXTS_HighestVModes_Labeled_DARM_and_ASC_Signals.png and - 2024-04-15_HXTS_HighestVModes_Labeled_DARM_and_LSC_Signals.png I claim that the mode at ~27.42 +/- 0.01 Hz is SRM in these spectra (id'ed at 27.45 Hz in LHO:49643), but PR2 and MC3 are closer possibilities (id'ed at 27.41 and 27.42 Hz in LHO:49643). To definitively assign these modes to suspensions, we'll likely have to do some driven tests at high frequency resolution.