Marissa Walker, Josh Smith, Alex Macedo, Oli Patane We looked at recent data to see if we could measure new violin mode frequencies. We used the DRMI 3f lock stretch mentioned in this alog . We made long (~10mHz frequency resolution) spectra of H1:LSC-DARM_IN1_DQ (Figure 1) and many ALS channels, but the violin modes were not clearly visible in any of them. We also measured spectra during a longer time from Aug 3rd (1217291534.25 to 1217297671.19) when there was ALS DIFF data but not DRMI, but again no violin modes were visible. So it seems, if we’ve chosen channels wisely, that the sensitivity is not yet sufficient to spot the new violin modes. We will continue to look at data as we get longer times and better sensitivity.
@DetChar -- thanks for the quick turn-around! Have you tried ALS COMM channels while Craig was measuring the COMM noise performance (see LHO aLOG 43214)? You can gather the time and channel to use from his DTT screenshot, and it looks like he used 10 averages for a 0.01 Hz bin-width data, so that should mean you can at least get 5 mHz resolution with 5 averages... Also, have you tried the looking through AS WFS?
Thanks for the suggestion, Jeff! I talked with Craig to get the time and channels, and made a higher resolution spectrum of the COMM noise from the same time, but still don't see the violin modes. https://ldvw.ligo.caltech.edu/ldvw/view?act=getImg&imgId=194662
Sheila and I saw violin modes in DARM starting at around 04/08/2018 6:10:00 UTC today.