Virgo Logbook

AdV-COM (AdV commissioning (1st part) )

casuaneva, magazzu, nardecchia, swinkels, tacca - 14:36 Saturday 26 January 2019 (44544)

52 Mpc!!!!!!

This morning Julia improved the BS alignment and fine adjusted the other AA working points. After a crisis of the OMCs (see operator report) we reached LN3 at 10.48 UTC with a maximum sensitivity of 52 Mpc!!!!

In the attached plot we compared the sensitivity curves of Jan 11st at 45 Mpc and of Jan 26th at 52 Mpc.

The improvement in all the bandwidth is evident.

Images attached to this report

Comments to this report:

mwas - 16:16 Saturday 26 January 2019 (44553)

The alignment work was an important contribution for getting the improved range.

Figure 1 shows that between yesterday and today the power on B1s2 dropped from 60uW to 40uW. B1s2 DC power is usually a good tracer of how much TEM10 56MHz is passing through OMC1.
The improved alignment allowed to exploit the low dark fringe offset (2.8mW of B1 power in total) without being spoilt by the 56MHz RIN contribution. In addition having all the light on one B1 PD lowered the electronic noise contribution, which also allows to use the low dark fringe offset to reduce the mystery "flat" noise.

Figure 2 shows that the 56MHz RIN (as sensed by B1s1) is a factor 3 below the noise curve for ~3mW on B1 PD2. Where last night for the same dark fringe offset the 56MHz RIN was about a factor 2 higher.

Images attached to this comment

verkindt - 17:27 Sunday 27 January 2019 (44569)

The following plots show the spectrograms of the channels Hrec_hoft_20000Hz and LSC_DARM between 10 and 400 Hz, when the BNS range is above 50 Mpc.

Plot1 : Jan 26 11:00 UTC : around 10:48 a first ramp of the BNS range, then, around 10:58 a second increase of the BNS range and a reduction of lines amplitude in h(t) spectrum.)

Plot2 : Jan 26 14:30 UTC : the BNS range reached again 52 Mpc

Plot3: Jan 25 21:30 UTC : the BNS range reached 55 Mpc. It is preceded by two glitches and a time period where the reconstructed h(t) has a lower spectrum

Plot4: Jan 26 18:30 UTC : the BNS range reached 62 Mpc. Again, it is due to two glitches that may have induced a h(t) reconstruction with a lower spectrum.

Images attached to this comment

robinet - 10:03 Monday 28 January 2019 (44574)

The recent data (Sunday and Monday morning) shows that it was not possible to geta BNS range over 50 Mpc. This is probably due to the bad weather conditions. The rate of scattered-light glitches at low frequency is huge (see fig. 1). UPV shows that the B7 signal is the most sensitive to these glitches.

Images attached to this comment

44574_20190128100337_20190128anaplotlscdarmfreqtime.png

bonnand - 10:54 Monday 28 January 2019 (44576)

Figure attached shows the position of the beam on the B7 camera over the week-end.

It seems that the beam was getting more and more far from the center of the camera.

The optical bench design is made so that the B7 Cam1 is in the same plane as the photodiodes. The photodiodes and Cam1 have been aligned respectively so that the beam is centered on the photodiodes when the beam is centered on Cam1.

We should adjust the angular setpoints of the bench to better center the beam on B7_Cam1 to avoid any clipping at the level of the B7 photodiodes.

Images attached to this comment

44576_20190128105201_b7beampositionweekend2627jan2019.png

bonnand - 11:34 Monday 28 January 2019 (44579)

A few minutes earlier, the ITF being in LOCKED_ARMS I took the opportunity to better align the B7 beam.

I adjusted the setpoints of SNEB to have the beam centered on SNEB_B7_Cam1 as following :

TX from -650 urad to -632 urad.
TY from -75 urad to -80 urad.

mwas - 12:49 Tuesday 29 January 2019 (44596)

Comparing Jan 11 and Jan 26.
Figure 2. To go from Jan 26 to Jan 11, at high frequency the situation is understood. Adding the electronic noise of the 2nd B1 PD, brings the noise from the Jan 26 to Jan 11 level.
But this not explain the improvement in the bucket.
Figure 1. To explain the change in the buck a F^0.25 noise with 5e-24 at 100Hz allows to explain the remaining difference.
Looking at fits from last year, the "flat" noise used to be at 7.5e-24 at 100Hz. So a reduction of 5e-24, means the remaining flat noise is
sqrt(7.5^2 - 5^2)*1e-24 ~ 5e-24.

In other words the flat noise was reduced by ~sqrt(2) between Jan 11 and Jan 26. And that reduction is not due to the understood B1 PD electronic noise.

Images attached to this comment

mwas - 14:00 Wednesday 30 January 2019 (44619)

Edit:
Found that the analysis below included a loud glitch in the middle (that causes a range drop). Shortening the data to avoid the glitch makes the 56MHz RIN subtraction work at most frequencies (still breaks down around the 50Hz and the violin modes)

Figure 3, shows the sensitivity before and after subtraction, with a small improvement visible between 80Hz and 200Hz.
Figure 4, shows the ratio between after cleaning and before cleaning, and there is up to 5% improvement in sensitivity in that band.
Computing the range, the cleaning gives a 2% improvement, so going from 52Mpc to 53Mpc.

--------- old
An additional note about the 56MHz RIN while at 52 Mpc.
Figure 1, as reported previously the measured coupling is about a factor 3 below the sensitivity curve. Using the B1s1 signal the 56MHz RIN can be removed, this is what makes the blue curve slightly below the red curve.

Figure 2, shows the ratio of h(t) after and before the subtraction of 56MHz RIN using the B1s1 signal. Below 100Hz the subtraction is clearly not working well, and is actually adding noise, but around 150Hz the noise is reduced by 3% because of the subtraction. Assuming the subtraction can be fixed, to have the same improvement above 100Hz without adding any noise below 100Hz, the impact on the range is still minimal. Even in that case the subtraction improves the range by only 0.7%, so from 52Mpc to 52.3Mpc. In other words the 56MHz RIN was not a large limitation last Saturday.

Images attached to this comment