At 13:10 I contacted the ISYS on-call (M. Gosselin) and we started to investigate the problem. As usual in this cases we tried to change some gains and finally at around 15:30 Matthieu found a configuration which allowed to reach LOW_NOISE_3_SQZ at 15:53 UTC.
At 16:00 UTC I started the planned calibrations with one hour of delay due to the previous problem; below the list of the calibrations:
- 16:00 UTC CALIBRATED_DF_PCAL, successfully completed at 17:24 UTC.
- 17:25 UTC READY_FREEMICH and then CALIBRATED_FREEMICH_WINI, successfully completed at 17:53 UTC.
- 17:55 UTC READY_DF_INtoEND_LN2 and then CALIBRATED_DF_INtoEND_LN2, successfully completed at 18:30 UTC.
- 18:32 UTC CALIBRATED_DELAY, successfully completed at 18:34 UTC.
- 18:33 UTC measure WE PCal timing;
- 18:36 UTC measure NE PCal timing;
- 18:38 UTC CALIBRATED_PRWI, completedy at 18:46 UTC
- 18:38 UTC CALIBRATED_PRWI, repetead under request of Dimitry, completedy at 19:07 UTC
All the calibrations completed at 19:09 UTC.
Then after some unsuccessful locking attempt the ITF was relocked in LOW_NOISE_3_SQZ at 19:42 UTC, but the sensitivity was very bad (Hrec_Range_BNS around 15 Mpc) and it looked like as the one in HIGH POWER; indeed the CoilSbWE and CoilsSbNE indicated different values on the VPM
I tried to unlock and relock without success.
At this point I contacted the SUSP on-call and from remote started to investigate the problem; we tried to stop and restart the processes CoilSbWE and CoilsSbNE.
Relock is in progress...
Other
periodic check of the shelved flags; here the repot
Downtime events (time in UTC)
from 13:10 to 15:53 because of fast unlocks.
Oncall events (time in UTC)
from 13:10 to 15:53 ISYS on site intervention because of fast unlocks; not clear if the problem has been completely solved.
from 20:00 to 20:50 SUSP on call from phone because of switching of Coil Relay not working; to be checked ...
After calibration of the timing of the PCals, the relay of NE was not properly switched off (from PCal_NE_Relay process). Hence the LED placed close to PCAL_NE_PD2 was still flashing the IRIG-B on the photodiode polluting the signal, which is the signal used to subtract the PCal lines in HRec. As a consequence this unexpected noise from IRIG-B was added in hrec instead.
The figure 1 shows the NE and WE PD1 and PD2 FFTs before and after I opened the NE relay to have it in its correct state. The PCal laser power loops was running correctly since they use PD1 power, but NE_PD2 was polluted.
On figure 2, before the fix, there was no coherence between PCal_NEB_PD2 and DARM, while coherence between PCal_NEB_PD2_power and Hrec.
We will add a flag in the DMS to check that the relays are off and the PCal PD2 channels are not polluted.
I have been acting on the master laser. First by resetting the noise heater (off then on again) and then by decreasing the current of the pumping diodes from 1.792 A to 1.772 A. The output power decreased from about 530 mW to 500 mW (see the attached plot). This does not impact the slave loop so much but reduces the number of possible glitches from the master laser.
