Virgo Logbook

Reports 1-1 of 1

AdV-ISC (Commissioning up to first full interferometer lock)

boldrini, bossilkov, ruggi, bersanetti, mantovani - 16:08 Monday 21 September 2026 (69783)

Recovery after DAS step

Today we attempted to recover the lock acquisition after this Sunday's DAS step.

We noticed that sidebands power has decreased at the DRMI step (Fig.1), but despite this the lock acquisition is somewhat workable without the need of any major change, although it tends to fail in STEP_3_OF_3 for reasons unclear.

The lock in CARM_NULL_1F is achievable, but not particularly stable. We noticed that a frequent cause of unlock is COMMp, who attempts to engage far away from its working point, possibly due to a slight misalignment of the SNEB that introduces a large DC offset in the error signal. For the moment, COMMp and the soft loops have been commented in ITF_LOCK.py (lines 4544-4545 for COMMp and 4458-4461 for soft modes)

Images attached to this report

Comments to this report:

mwas - 9:22 Tuesday 22 September 2026 (69790)

To attempt to help with COMMp, yesterday at 14h53 UTC I have increased the SNEB drift control loop gain by a factor 2. The loop error signal is power normalized, so this is not intended to compensate a loss of loop gain due to low power, but to actually increase the loop gain.