Virgo Logbook

Interferometer_sensitivity_studies (General)

Paoletti, chiummo - 18:06 Monday 04 September 2017 (39373)

Tapping tests in DET Lab

This morning, as scheduled, we performed some tapping tests starting from DET Lab.

The tapping was performed by means of calibrated hammer, without exploiting the piezo trigger. First spots explored are shown in pictures 1,2,3, highlighted with red circles/arrows. Also, we attach a couple of spectrograms of the closest accelerometers (ENV_SDB2_ACC_Y and ENV_DT_ACC_Z) together with hrec and DARM for the two periods of tapping, you can easily spot the actual tapping by looking at the accelerometers signals in pictures 4,5.

GPS times for the actual tapping are given below along with some notes:

Federico hammers standing on the south side
Time: Sep04,17-11:19:07 -> GPS: 1188551963
DT flange z (see picture 1)
Time: Sep04,17-11:20:32 -> GPS: 1188552048

Time: Sep04,17-11:23:45 -> GPS: 1188552241
SDB2 flange z (see picture 2)
Time: Sep04,17-11:24:55 -> GPS: 1188552311

Time: Sep04,17-11:25:30 -> GPS: 1188552346
north link (picture 3)
Time: Sep04,17-11:26:32 -> GPS: 1188552408

Time: Sep04,17-11:27:58 -> GPS: 1188552494
north link -1 (picture 3)
Time: Sep04,17-11:28:58 -> GPS: 1188552554


Time: Sep04,17-11:30:11 -> GPS: 1188552627
north link - 2 (West side) (picture 3)
Time: Sep04,17-11:31:06 -> GPS: 1188552682


Time: Sep04,17-11:31:36 -> GPS: 1188552712
north link - 2 (East side) (picture 3)
Time: Sep04,17-11:32:29 -> GPS: 1188552765



Time: Sep04,17-11:33:05 -> GPS: 1188552801
north link - 3 (picture 3)
unlock!!!!
SDB2 bench controls opened?!?!

Re-lock, Federico hammering from the north side
Time: Sep04,17-12:08:29 -> GPS: 1188554925
north link (large shoulder up to ~100Hz)
Time: Sep04,17-12:09:28 -> GPS: 1188554984


Time: Sep04,17-12:11:04 -> GPS: 1188555080
north link -1
Time: Sep04,17-12:11:48 -> GPS: 1188555124

Time: Sep04,17-12:12:17 -> GPS: 1188555153
north link -2 West side (structures excited @300 - 400Hz)
Time: Sep04,17-12:13:03 -> GPS: 1188555199


Time: Sep04,17-12:13:26 -> GPS: 1188555222
north link -2 East side(it touches north link -3)
Time: Sep04,17-12:13:55 -> GPS: 1188555251


Time: Sep04,17-12:14:29 -> GPS: 1188555285
north link -3 (huuuuuuuge effect)
Time: Sep04,17-12:14:52 -> GPS: 1188555308


Time: Sep04,17-12:16:28 -> GPS: 1188555404
north link -3 (softer hammer tip) huuuuuuge effect
Time: Sep04,17-12:16:52 -> GPS: 1188555428

unlock again!!!!

Images attached to this report

Comments to this report:

fiori, paoletti, chiummo - 8:27 Tuesday 05 September 2017 (39377)

A quick look to data shows that, while the so called "North-3" link pipe is the most sensitive giving rise to shoulders (Figure 1) and eventually excite SDB2 controls, hitting the link pipe "North-2" rises several Hrec structures (in particular the 408Hz peak!) (Figures 2 and 3). Similar excitations occurr (but a bit less) when hitting the link pipe "North" and the DT flange. While nothing happen when hitting the link pipe "North-1" or the SDB2 flange.

Concerning the "North-2" pipe, the West side (Figure 2) seems a bit more sensitive than the "East" (Figure 4).

If repeated, it might be interesting to stick one small accelerometer to the pipes.

Images attached to this comment

bonnand - 15:49 Tuesday 05 September 2017 (39383)

Concerning those mini-links they are equiped with viewport, 2 on the SDB1 (DT) side and 2 on the SDB2 side, they are tilted vertically by 2 degrees.

The 2 on the SDB1 side are the so-called "north" and "north-2" pipe which are quite sensitive to excitations (lines and structures rising in DARM).

So it seems that exciting the DT flange or those 2 "north" and "north-2" pipes (especially on the west side) you excite the viewports located inside the SDB1 tower.

It can be assumed that scattered light coming from reflections on those viewports gets more easily coupled back to the ITF compared to the one on the viewport "north-1" which contains only the hartman beam and has its viewport on the SDB2 side.

The reflections from the viewport "north-2" (pipe containing B1p, B1s1 and B1s2 beams) are being dumped by black glass located on SDB1 whereas it is not the case for the B5 viewport.

Concerning the "north-3" pipe, its viewport is located on the SDB2 side, but it is the B1 beam pipe so it is not very surprising that it is very sensitive to excitations.

bader - 10:18 Friday 22 September 2017 (39543)

Below are the noise budget plots for tapping tests on different mini links

1) North link (1188554325), large shoulder up to about 100 Hz
2) North link - 1 (1188555080
3) North link - 2 west (1188555153), structures excited at 300 - 400 Hz
4) North link - 2 east (1188555251, touches north link - 3
5) North link - 3 (118855404), huge effect, large shoulder up to 400 Hz

The NB plots lead to the conclusion that scattered light form the SDB2 bench is fed back to the detector when exciting the B1 mini link.

Images attached to this comment