evan.goetz@LIGO.ORG - posted 11:34, Friday 06 March 2020 - last comment - 12:37, Friday 06 March 2020(55473)
Concerning uptick in 1 Hz comb in recent data starting Feb. 26
Since there has been recent activity adjusting EX electronics to try mitigating some of the narrow lines and combs, I've been trying to check in periodically with the comb tracking page (see H1 summary page "DetChar: Combs" tab). While adjustment work and investigations are still ongoing, I noticed a concerning uptick in the 1 Hz comb prevalence. Attached is a plot from the comb tracking page that shows an uptick starting February 26. I'm concerned there was some adjustments that have increased some coupling, but I can't point to an exact culprit. Fil's aLOG 55291 from Feb. 25 said there was a change in the 24V supply for the safety chassis. Could this have caused something to change or added anything?
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Taking a look at the spectra, I suspect this may actually be an uptick in a 16 Hz comb, which shows up on the 1 Hz tracker plot. A brief look through the magnetometer data for today indicates that the 16 Hz comb is present in a lot of EX magnetometers, and there are hints of it in CS magnetometers as well. I haven't seen evidence of it at EY. Again, I've only done a quick check by eye of one of the magnetometer channels (H1:PEM-EX_MAG_VEA_FLOOR_Y_DQ), but the comb does seem to appear (weakly) on the 25th and strongly on the 26th.