Virgo Logbook

AdV-AEI Squeezer Integration (external squeezer table)

sorrentino, vardaro - 10:30 Tuesday 11 December 2018 (43978)

Excess of noise when the Faraday SDB1 shutter is open

We investigate the effect of the stray light from the ESQZ bench opening the SDB1 Faraday shutter.

The measurement is performed in two time, yesterday evening between 18:00 and 19:30 UTC and this morning between 6:00 and 7:00 UTC.

The GPS time of the measurement are:

- shutter closesd yesterday: 1228504012 about 30 min of data

- shutter closed today: 1228517955

- shutter open yesterday: 1228501685 we have about 6 min of data

- shutter open today: 122854697

We investigate if some effect of the stray light is visible in Hrec. In the attached first plot

- blue curve: shutter open today

- green curve: shutter open yesterdat

- orange curve: shutter closed yesterday

- red curve: shutter closed today

Comments

- Attachment 2: is a screenshot of the Near Camera of the SQZ bench and shows that the shutter was no well closed

Images attached to this report

Comments to this report:

fiori - 10:56 Tuesday 11 December 2018 (43983)

the structures at 101Hz and 157Hz (and 198Hz) that are higher when the shutter is open seems the famous peaks that we suspect to be modes of SIB1 (at least 101 and 157Hz) and whose coupling to DARM was found to correlate with mistuned FModErr:

zendri - 15:30 Tuesday 11 December 2018 (43994)

The AdV sensitivity worsening when the SDB1 shutter is open seems to be a transitory phenomenon.

For instance, in the attached plot you can see how this effect was absent few days ago.

Magenta: Today, SDB1 shutter closed
Blue: 2 Dec, SDB1 shutter open

Compared to the closed shutter configuration the blue curve looks better even if two additional peaks are present above 1 kHz.

In both cases the alignment with the squeezer was not optimal. However it is probably different from case to case because the auto-alignment
loop is not yet operational.

Images attached to this comment