andrew.lundgren@LIGO.ORG - posted 15:19, Wednesday 26 July 2023 - last comment - 11:04, Thursday 27 July 2023(71739)
Jitter glitches discovered by GravitySpy volunteers
Marissa, Shania, Tabata, Gaby, Brennan, Andy GravitySpy volunteers noticed a new type of glitch that happened on May 31 and June 1 (GSpy link). Many of these glitches appeared as a high-Q line at 590 Hz, but they also appear as a stack of high-Q lines in the 100 to 600 Hz range, and sometimes only below 300 Hz (plot 1). The cause seems to be physical motion of the PSL periscope (plot 2) in short bursts. The coupling to DARM is through the periscope motion causing beam jitter (plot 3). The MCL/REFL_SERVO loop are also witnesses. Some of the glitches in the periscope are broadband, while others have a few well-defined frequencies (plot 4). There was an increase in the motion of the periscope during this period, seen by BLRMS of the periscope accelerometer (plot 5). The motion was still elevated above the previous level when this period ended. This kind of jitter glitch has occurred again in short bursts in some later days, but not for sustained periods. Scans of selected times are at this link (needs LVK login). Note that this configuration does not include the jitter or periscope accelerometer channels.
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We also see in some of these glitches a loud noise in HAM1 HPI and LVEA floor accelerometer channels. See the attached example omega scans showing one glitch from June 26 showing up in H1:HPI-HAM1_BLND_L4C_Y_IN1_DQ and H1:PEM-CS_ACC_LVEAFLOOR_HAM1_Z_DQ. You can also see other accelerometers showing up in the full omega scans here but those were ones that showed up especially strong in several of the glitch times we examined. These are obvious in the omega scans at the specific glitch times, but this motion can't be clearly seen in the day-long spectrograms in the summary pages.
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