Reports until 08:19, Friday 04 December 2015
H1 AOS (DetChar)
joshua.smith@LIGO.ORG - posted 08:19, Friday 04 December 2015 - last comment - 12:09, Saturday 05 December 2015(23950)
Investigating whether low-frequency glitches from Dec 3 are scattering

In 23939 Evan pointed out low frequency glitches. These look very similar to the scattering glitches seen at LLO every day (there likely driven by OM suspension motion). I think these gltiches at LHO are probably related to SRM or PRM optic motion for a few reasons. 

Figures 1 and 2 show the SNR/Freq plots from hveto of Strain and Mich, respectively. These both show a relationship between amplitude and SNR that is what you expect for driven fringes/shelves sticking out farther above the noise, the higher frequency they are driven to. 

Figures 3 and 4 show omega scans of Strain and Mich showing pretty clear arches. The arches are stronger in Mich than in Strain (in terms of SNR). 

Figures 5 and 6 show the fringe frequency prediction based on the velocity of the PRM and SRM optics. The period is about right for both. The results for other optics are shown here. The code is here. And the scattering summary page for this day is here. The dominant velocity looks like about 0.15Hz judged by eye from the timeseries. 

Figure 7 shows that during the glitchy times (green and yellow) the SRM and PRM optics are moving more at about 0.12Hz (probably compatible with the largest velocity frequency above). There's also a pretty strong 0.6Hz resonance in PRM, but this is the same in good and bad times. 

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bas.swinkels@LIGO.ORG - 12:09, Saturday 05 December 2015 (23973)DetChar
I ran EXCAVATor over a 4 hour period when the low-frequency glitches were visible, see the results here. The top 10 channels are all related to SRM, but the absolute value of the derivative (as usual in case of scattered light) of H1:SUS-SRM_M2_WIT_L_DQ wins by a hair and also seems to have a decent use-percentage. Using this channel as a veto, most of the channels related to SRM drop in relevance in the second round. This round is won by H1:ASC-DHARD_P_OUT_DQ with some signals related to ETMX/ITMX close behind.