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AdV-COM (AdV commissioning (1st part) )
pinto, spinicelli, nardecchia, was, ruggi - 20:41 Monday 09 March 2026 (68848) Print this report
ITF recovery

Today we continued the recovery of the ITF. We managed to reach LOW_NOISE 2.

At the beginning we noticed a lower power values on the 112 and 12 MHz sidebands, which was taken care of by Ilaria, acting on CH:

NI CH = 0.577W -> 0.708 W

WI CH = 0.324 W -> 0.416 W

At the end, we partially reversed the NI CH PWR increase: 0.708 W -> 0.630 W. (17.32 UTC finish of the actions).

After this, we had several issues in finding a good configuration of demodulation phases in order to get past the handoff from 3f to 1f in CARM null. In particular DIFFp was showing during the transient some misbehaviour (not entirely clear the rigth explanation), in which with good phases both I and Q (on TX DoF) were witnesses of some movement which ended up in a quick drift of the alignment and eventually the unlock. Curiously enough, the phase able to get past the initial transient was showing a ~45 deg mistuning. After several trials in which we noticed this behaviour, we implemented a double condition in the automation in which we use two phases, one 'wrong' for the transient and one good for the steady state (similarly to what we do for B4 56 MHz).

With this configuration we were able to lock the OMC, after a tuning of the OMC locking phases, and go up to LOWNOISE 2. However, after a while we unlocked due a to a WI tower pump failure. Antonio went to CEB  to take care of it.

We leave the ITF locking on LOWNOISE2 for the night, to acquire some statistics on the acquisition.

N.B. the modification on the automation are the following:

ITF_LOCK.py: added lines 4681-82; 4685-86.

ITF_LOCK.ini, in the SHUTTER section: added the steady state DIFFp phases.

If the acquisition is robust enough, tomorrow we will proceed to fine tune all the several phases, if needed.

:)

Comments to this report:
bersanetti, casanueva, mpinto, spinicelli - 9:43 Wednesday 11 March 2026 (68860) Print this report

Yesterday, after the weekly maintenance, we continued working on the full recovery of the ITF.

During the night before, the ITF has been put in Locked arm due to troubles in locking even in carm null. The issue was due to the demodulation phase of the Diffp (mainly the TX DoF ). However, as the previous day, we could survive during the transient only using a "bad" phase (slightly different from two days ago), with most of the signal on the Q quadrature. 

Moreover, looking at the phase camera, we saw some jumps of the sidebands, similarly to what we had when the PR Chrocc was mistuned. Looking at the usual PR Chrocc observarbles, both current and heater temperature probes were higher then the values before power outage (see fig. 1). Thus, we decided to perform a small step down (~0.05V ), at 14h12UTC. 

During the whole afternoon, we could stably reach CARM_null_1f, but the step on chrocc didn't show any macroscopic improvement to the cleanness of the locking signals. 

We tried few times to continue to LN2, with success. However, as the day before, the locks in LN2 lasted only ~10 minutes, with the interferometer unlocking without a clear reason (some of the longitudinal DoF drifting away).

Finally, the lock acquisition continued to have problem during the night. The work on it will continue also today. 

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