Virgo Logbook

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

fiori, nocera, pasqualetti, aiello, dattilo, boschi, travasso, flood, koley, montanari, soldani - 20:01 Thursday 20 July 2017 (38725)

results of today switch off

Summary: today we performed a switch off of several infrastructure machinery and electronic devices. At the of the day seems we improved DARM at the 45Hz and the 90Hz bumps, and we also understood the origin of some lines. BUT we worsened the DARM noise at and around 50Hz.

The switch off was done in sections, with this sequence:

between 7:35 and 9:01 UTC: air conditioning of WEB, NEB, MCB and CEB was switched off (including Wi-Fi in experimental halls, the photon calibrator and SWEB, SNEB fans - SPRB was already off): see detailed timing. Then all HVAC stuff, fans and the photon calibrator was switched back on between 9:12 UTC and 9:40 UTC (this last time is rough). Wi-Fi was switched back on at 14:25 UTC.
9:45 UTC (end time): VAC stopped the cooling fans of turbo pumps at PR, BS and PR-BS link
10:45 UTC (end time): VAC stopped the HVAC cooling fan of the 'remote pump' room in CEB (restarted at 13:30 UTC)
11:30 UTC (end time): VAC stopped all the remaining active cooling fans of CEB turbos: IB; DT;SR;NI;WI (both types, industrial ones and 'home' type ones) (see also here for VAC times). Then VAC restarted all the fans (finished at 14:30 UTC) in particular implementing some seismic isolation of the cooling fans of the PR turbo and of the PR-BS link turbo.
switched off some un-necessary electronics in CEB, NEB, WEB (time list to be added)
between 13:05 UTC and 13:24 UTC: some TCS devices in TCS room and also on NI and WI TCS benches (see timing here)

The switch off #1 (HVAC) produced the disappearing of lines at 6.5Hz, 24.6Hz, 36.3Hz (photon calibrator) and 207Hz, as reported in origin of some lines

The switch off #2 (PR, BS and PR-BS turbo p. fans) produced the reduction of a bump around 45Hz in both DARM, MICH and PRCL, associated to the removal of a pair of seismic lines around 45Hz in the accelerometers at PR, PR-link, BS, PR B4-GHOST and SPRB-link: see Figure 1.

The switch off #3 (HVAC fan of remote scroll room) did not produce macroscopic effects in DARM, yet possible effects in ENV sensors have to be investigated.

The mitigation of the turbo pump fans did produce some effect (seismic peaks are still visible in ENV_B4_GHOST_ACC put about 10 times smaller). see VIM spectrogram in Figure 2. The Bump in MICH is still present but reduced: Figure 3.

The switch off #4 (other VAC cooling fans) did not produce a macroscopic effect in DARM (ENV sensors yet to be analyzed)

At 13:03 UTC the ITF was relocked, after the switch off #5 and #6 (electronics and TCS), and we noticed an increase of the 50Hz line and the bump around it. Figure 3.

Finally, a few minutes after 14:00 UTC, a seismic line at 92Hz disappeared from CEB sensors (see VIM spectrogram in Figure 4), correspondently the bump at 90Hz disappeared from DARM, MICH and PRCL: see Figure 5. The switch off of the 92Hz source is not part of the controlled switch off. To be investigated.

Also to be investigated is the origin of the 50Hz extra noise. The actual plan is to perform a selective switch off of electronics devices to localize it. Possibly tomorrow.

Concerning the disappearence/reduction of 45Hz and 90Hz bump, this seems consistent with the hypothesis of scattered light from B4-GHOST and indications of the projections.

Images attached to this report

38725_20170720195755_turbofansafterelectronicsoffanddumpofturbofans.gif

38725_20170720195803_spectroenvb4ghostaccz5011086400.jpg

Comments to this report:

cleva - 8:10 Friday 21 July 2017 (38730)

I don't know whether this has been tried in the past but switching off the chiller of the slave laser for a while (< 60 sec) could be attempted with no damage.
it is just a matter of short circuiting the safety chain at the releavant port (24V power suppply used for the PID in the slave laser rack).
The same test for the 60W amplifier chiller may also be considered, although I don't know the safety logic for this system.
I did it in Nice with no pb at all.

This test could be considered after O2 during the debriefing phase
(of course not in the present period)

genin - 9:22 Friday 21 July 2017 (38731)

It is not possible to switch off the main chiller because it is also used to cool the laser amplifier crystals and there are no Peltier cell in the LA optical head.

Regarding the laser amplifier chiller, there are some internal checks at the level of the control electronics which will switch off automatically the laser amplifier if the

chiller is switched off...

schaaf - 9:25 Friday 21 July 2017 (38732)

Timings of switching back on phase camera:
18:08 switch on electronics
18:30 images recovered (by increasing scanner radius and restarting FPGA processes)

Vacuum - 11:26 Friday 21 July 2017 (38736)

the 92Hz line disappearing can be related to one of these operations we have done during the restart ( the timing is corresponding):

_ inspection of a compressed air connector leaking air near PR tower (hissing sound maybe slightly changed)

_ disconnecting of a turbo controller on the SR-BS rack (the pump was OFF, the controller was connected to the mains, it includes a cooling fan).

This could be checked during next maintenance break, looking at accelerometers while repeating same operations

flood, fiori - 11:47 Friday 21 July 2017 (38738)

A further analysis of the mysteriously disappearing 92Hz bump in DARM has been done. Attached are Figures 1,2, & 3 which show spectrograms of DARM, MICH & PERCL respectively. There is clearly a decrease in noise around 92Hz in all of them. Figure 4 looks at the accelerometeters around the PR tower before and after the disappearing bump. There is a line at 92Hz in the PR accelerometers that has disappeared. Lastly figure 5 is a spectrogram of the SPRB_LINK_ACC which was used to pinpoint the time the line disappeared to 14:19:49UTC ±1s (1184595607). Correlated in time to some VAC switch offs (38736).

It is also worth noting there appears to be 6 drifting lines in PERCL (3 pairs of lines all drifting in the same way), the clearest lines are Figure 3 around 115Hz. By eye these do not seem correlated to any F7 temperature sensors and are drifting significantly over a day. These lines can be very faintly seen in LSC_DARM. Is this an issue with aliasing even though we don't see mirror images? There is also some change around 80Hz in Figure 1 (LSC_DARM) that is not yet well understood.

Images attached to this comment

nocera - 13:52 Friday 21 July 2017 (38747)

For future reference, here's the list of devices switched off yeterday afternoon during the last part of the morning shift:

CB Hall Particle Counter

SBE
SIB2 electronics and stepper motors (DAQ Room)
EIB-SAS electronics and stepper motors (EE Room)
SPRB stepper motors (DAQ Room)
SNEB stepper motors (NE Hall)
SWEB stepper motors (WE Hall)

TCS
Power Stabilization Photodiode power supply (TCS Room)
CO2 Benches Flip Mirror system power supply (TCS Room)
SMC Pollux Box Rotor Driver (TCS Room)
PSD Readers (CO2 bench, both NI and WI)
Power Meter (CO2 bench, both NI and WI)
Ring Heater power supply (WE, the one at NE was already off*)

*see next entry

nocera - 13:56 Friday 21 July 2017 (38748)

The 50 Hz miracle

After last part of yesterday's switch off shift, our beloved 50 Hz nightmare was again with us.
Basically, we switched stuff off and that made it worse.
After narrowing down the possible short list of actions which could have potentially caused it, today we carefully tried to undo them.
It looks like it was a success.
What allowed us to go back to the previous situation (actually, slightly better: light brown before, magenta after, blue today after the miracle)
was reconnecting the power supply cable to the NE Ring Heater power supply.
It is worth mentioning the power supply itself was (and still is) off.

Science marches on.

Images attached to this comment