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Reports until 16:34, Wednesday 30 October 2024
H1 General (ISC, Lockloss, PSL)
camilla.compton@LIGO.ORG - posted 16:34, Wednesday 30 October 2024 - last comment - 09:28, Monday 11 November 2024(80951)
IMC tagged Locklosses

Reran all O4b locklosses on the locklost tool with the most up to date code, which includes the "IMC" tag.

The locklooss tool tags "IMC" if the IMC looses lock within 50ms of the AS_A channel seeing the lockloss (example plots in 80561).
Note that we don't know that the IMC is causing the lockloss but we are sure that this lockloss is different from the typical lockloss where the IMC loses lock ~250ms after the IFO (seen by AS-port).
Vicky, Sheila and I did some trending this morning and found no conclusions of whats causing the locklosses, we checked that the fast shutter itself isn't causing the lockloss (via HAM6 SEI GS13's) and it seem like in the milliseconds of the lockloss, the AS power decreases and excess power goes to the REFL port.

I used the lockloss tool data since the emergency OFI vent (back online ~23rd August) until today and did some excel wizardry (attached) to make the two attached plots, showing the number of locklosses per day tagged with IMC and without tag IMC. I made this plots for just locklosses from Observing and all NLN locklosses (can include commissioning/maintenance times), including:

Images attached to this report
Non-image files attached to this report
IMC_locklosses_sinceAugust.xlsx
Comments related to this report
camilla.compton@LIGO.ORG - 09:49, Thursday 31 October 2024 (80965)ISC, Lockloss
Link

Attaching plots from zooming in on a few locklosses:

Time Tags Zoom Plot Wide Plot
2024-10-31 12:12:26.993164 UTC (IMC) OBSERVE IMC REFINED annotated plot plot
2024-10-30 12:16:33.504883 UTC (IMC) OBSERVE IMC REFINED annotated plot plot
2024-10-30 16:09:21.548828 UTC (Normal) OBSERVE REFINED OMC_DCPD N/A annotated plot

The 10-31 zoom plot notes the framerates of the channels: ASC, REFL and NPRO_PWR are 2kHz and GS13 is 4kHz, the others are 16kHz.

  • In the "NORMAL" lockloss (nearly 100% of locklosses since O4a and O4b before OFI vent):
    • The arm signals (ASC_AS_A/C) increase over 10's ms as the REFL signal decreases.
    • ~250ms later the PSL channels change and the IMC looses lock. 
  • In the "IMC" lockloss (25% of locklosses since OFI vent):
    • The arm signals (ASC_AS_A/C) suddenly (<0.5ms) decrease as the REFL signal increases.
    • At the same time the PSL signals change.
    • <10 ms later the IMC looses lock.
Images attached to this comment
sheila.dwyer@LIGO.ORG - 11:31, Thursday 31 October 2024 (80975)
Link

Since September 18th we've had 21 locklosses from NLN tagged as FSS_OSCILLATION, of these 20 also had the IMC tag.   Since September 12th, we've had 49 locklosses from NLN tagged IMC, so roughly 40% of these IMC locklosses have the FSS oscillation tag, since the NPRO was swapped we don't have any tagged with FSS_OSCILLATION. 

(Reminder, the FSS_OSCILLATION tag is an old tag, intended for a different problem, but it tags times where the FSS fast mon goes above a treshold.)

camilla.compton@LIGO.ORG - 09:28, Monday 11 November 2024 (81191)
Link

Updated plot attached of NLN locklosses tagged with and without the IMC tag. 

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