Virgo Logbook

Detector Characterisation (Spectral lines)

fiori, tacca - 10:36 Wednesday 04 September 2019 (46834)

peaks 48.05 and around 42Hz increased amplitude

Hrec peaks at 48.05Hz and the bunch of little peaks around 40-44Hz all increased significanly in amplitude starting from the first lock of yesterday (sept 3) AFTER MAINTENANCE.

This extra noise is visible in spectrogram: Figure 1 and also in the spectrum: Figure 2

It is not certain that this extra noise can explain the 2Mpc we lost yesterday.... to be better checked: Figure 3

From previous investigations, we have clues that these mentioned peaks originate from WE (see Paolo's about 48.05Hz, and this about the 40-44Hz ones)

among the actions list of yesteday there is one that has the "WE" name in it, that is: WE UPS2 repair ... this of course might well be a wrong clue, but worth to check...

Images attached to this report

Comments to this report:

ruggi - 19:31 Friday 06 September 2019 (46854)

48.05 disappeared on Sunday AUG 25 after a mysterious huge event visible in DARM at 8:38:21 UTC (gps 1250757519, fig 1). The event was followed by a slow ring down of the peak (fig 2), and then the peak was no more there (or much lower, fig 3) for several days. Very nice, the spectrum of DARM during the event (fig 4).

At a first fast look, everything seems quiet in SUSP_WE, SWEB and ENV_WEB signals. Some brute force search might help.

Images attached to this comment

swinkels - 16:21 Saturday 07 September 2019 (46858)

A quick omicron scan does not show a corresponding glitch in any channel other than the expected ones.

fiori - 23:01 Monday 21 October 2019 (47306)

As Federico noted in 47179, switching on the faulty UPS of WEB on Sept 3rd caused an increase of ambient magnetic noise nearby WE vacuum chamber, which is larger since then. It is maybe worth noticing that consequently there was an increase of noise in Hrec, coherent with this magnetic field, not only at the 41-43Hz peaks but also around the 48Hz peaks and a bit up to 55Hz, see the attached plot.

Images attached to this comment