KAGRA Logbook

MIF (General)

takafumi.ushiba - 8:58 Tuesday 17 June 2025 (34257)

ISC WD doesn't seem to work during ALS_DARM lock

I realized ISC WD doesn't seem to work well when IFO was locked with ALS_DARM.
Figure 1 shows the ISC WD signals when IFO went DOWN during the lock acquisition.

Even though IFO failed to lock, ISC WD signals (blue line in the top graph) doesn't touch the threshold (red line in the same graph).
It causes a large kick of the suspensions, which results in the long interval to the next lock trial to wait for the suspension calm down.
To improve the situation, it would be better to try to set ISC WD with proper threshold.

Images attached to this report

34257_1750118107_Screenshot from 2025-06-17 08-53-30.png

Comments to this report:

takafumi.ushiba - 9:18 Tuesday 17 June 2025 (34258)

I updated the ENGAGE_ALS_DARM state of LSC_LOCK guardian.
Now, ISC WD is set as 90,000 during ALS_DARM lock.
It should be checked the stability of lock acquisition with this condition.

Images attached to this comment

34258_1750119459_Screenshot from 2025-06-17 09-16-07.png

takafumi.ushiba - 14:21 Tuesday 17 June 2025 (34262)

I found that trigger signals of ISC WD sometimes became larger than the threshold at ENGAGE_PRMI_3F state and caused the unnecessary lockloss (fig1).
So, I modified the guardian again so that set WD threshold as 150,000 at ENGAGE_ALS_DARM state (fig2) and reduce the threshold to 90,000 at PRMI_3F_LOCKED state (fig3).

Images attached to this comment