Virgo Logbook

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

bersanetti, boldrini, casanueva, masserot, spinicelli - 0:11 Tuesday 26 March 2024 (63734)

ISC shift: recovery after INJ reset

After the restart of the INJ Acl server, De Rossi and Gosselin spent a long time recovering the injection.

Once they gave the green light, we continued with the lock acquisition, but noticed that the arms would not engage the lock loop.

Masserot discovered a bug in the current build of Acl that would prevent any "load" command sent to a Sum or Matrix channel. He rolled back the previous version of Acl on every server contacted by the ISC metatron node. He did not do the same thing for the SQZ servers, so it won't be possible to go to LN3_SQZ until the issue is fixed.

We noticed that the green laser is particularly glitchy (Fig.1)

After a few failed lock attempt, we realized that a noise injection on SSFS driving was left on.

After turning it off the lock acquisition worked fine.

During this occasion, Masserot noticed a logic error in ITF_LOCK.py, lines 4310-11 (lines injection on SSFS). This version of Acl does not allow to send two consecutives commands to a Sum channel. We emporarily substituted them with a cm_send that changes both the weights of the two lines in SSFS.noise_driving_rtpc.

We leave the ITF in LN3

Images attached to this report

Comments to this report:

derossi, gosselin - 10:08 Tuesday 26 March 2024 (63737)

The recovery of the injection took longer than usual because when we unblocked the beam, dumped as usual at the output of the PMC with the PMC in scan, the system was unstable with the PMC and IMC unlocking continuosly.

We did all the usual checks to exclude the different loops (we opened the PSTAB, the IMC AA, the RFC, checked the IMC loop working points). At the end the IMC restarted to lock.

We thought that the increase of temperature on the LB had produced a horizontal misalignment at the output of the NEOVAN (plot 1), but since we did not remember such kind of issue, we looked back in the data of the 3rd of Feb (beam blocked to work on EIB suspension) and we found out that we had similar increase of temperature and drift of the NEOVAN, but that time the IMC relocked straight (plot 2).

We measured the OLTF of the IMC (both digitally, and I forgot the noise on, this is one of the reason why the ISC crew had problems with the relock) and analogically. The phase margin was lower than the last times we measured it (9° instead of 17°) (plot 3)

At the end we checked the Fmoderr and we left the system as it was before the shift. We did not understand yet the origin of the issue we encountered.

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derossi, spinicelli - 14:48 Tuesday 26 March 2024 (63742)

In order to understand why the IMC OLTF has changed since the 4th of march (UGF at 107kHz with a phase margin of 16deg, #63487), this morning we tuned the angular and longitudinal working points of the IMC loop (plot 1).

We remeasured the OLTF but it was the same as yesterday (84kHz UGF and 10deg phase margin, plot 2).

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