Virgo Logbook

Injection system (General activities)

gosselin, derossi, lagabbe, melo, spinicelli, cavalieri, ballardin - 8:51 Tuesday 03 March 2026 (68788)

INJ PSL recovery

Entry front yesterday evening that somehow remained in the drafts :

Today we went on with the recovery of PSL/INJ systems after the black out of this weekend.

Chillers :
- restart of the termotek for neovan head
- restart of the chiller for neovan electronics.
- OMI main chiller for other components restarted by itself, flow is lower than before shutdown.

EIB : restart the generator situated in the EEroom on the rack on the right : set the frequency to10 kHz and voltage to 5Vpp.
Open and close the actuation and PID. The bench went back to its position.

LNFS : the main LNFS was not working. We had to swap it with the spare one.

ML : restarted without troubles. Temperature is set by the knob on the front end and should have remained the same (to be checked). Pumping current was set with the knob and was set using the values of the dedicated channels

Fibered EOM : we restarted (OFF/ON) the power supply (in the corner of the atrium)

Pre-amplifier : restarted withtout any troubles

DDS for 14 MHZ : restart freq 14.48 MHz, DDS out 58.

Neovan : restart the pumping diodes without any problems.

SL :
- In EER, decrease the current of the pumping diodes
- ON on the power supply (upper part of the rack), safety chain reset => ok
- flip the mirror between SL and AMP
- Increase the current of the pumping current. Values slightly different from before black out but REFL ok

At that point we decreased the power going from SL to AMP with the HWP and slowly increased the power seeding the neovan
The power of the neovan was slightly lower but we let it like that for now, waiting for thermalization and further intervention if needed. (0.34 V instead of 0.358 V when writtig this line)

Then we relocked the PMC and slightly realign it.
We freed the beam towards on the EIB and relock the IMC.

We had to realign the IMC manually. Initially, we were unable to engage the AA.
After investigating, we realized the issue was similar to the one encountered during the previous shutdown: the electronics used to calculate the QPD NF asymmetries were not functioning properly. Although everything appeared normal at first glance. Doing off/on was sufficient to restore its normal operation.

We restarted the ethernet bridge to commumicate with the PZT drivers of the RFC. The drivers were Offline, we put them back Online and set the values of the PZT back to where they were (VPM).
The RFC was not relocking, we readjusted the phase by 0.9 rad (python), we adjusted a bit the alignment but more need to be done.. We tried to adjust : threshold (PWR RFC on MCCDMir DSP card), gain loop... but for now we can not relock it.... To be continued

Comments to this report:

gosselin, melo, spinicelli, lagabbe - 14:32 Tuesday 03 March 2026 (68799)

This morning we continued with the recovery.
Yesterday evening the photodiode for RFC REFL was not correctly responding, we could see some signal but it was actually off. Romain restarted it yesterday evening.
Thi fixed, we managed to relock the RFC. We had to readjust again the demodulation phase. At the end of the day it was the same than before the black out.

Having relocked the RFC we tried to realign it but did not manage to get more than 2.6 V on RFC TRA using both axis of both PZT... to be furhter investigated

We also checked and adjusted the 56 MHz demodulation phase for fmoderr as well as its mechanical and freq calibrations.

gosselin - 16:07 Tuesday 03 March 2026 (68806)

I tried again to realign the RFC with the PZT. I got a slightly better transmission mainly using M16.

M15 seems more problematic. We are already at 120 V on the y axis.
Strangely the x axis does not seem to have any effect on the power in transmission (figure).

The power is still quite far from what we had before the black out. From the camera in reflection it seems that we have some vertical misalignment.

Images attached to this comment

68806_1772550316_Screenshot 2026-03-03 160135.png

gosselin, melo, lagabbe - 19:04 Wednesday 04 March 2026 (68818)

This afternoon we tried to drive the M15_axis_x with a different PZT driver.
We first brought the corrections to 0V with the command online and this had a positive effect on the RFC TRA (green arrow on the figure 1).
Then we connected the lemo1 cable of the PZT axis to the other driver that was also set to 0V and again this had a positive effect on RFC TRA (yellow arrow).
This strange behavior might be due to some hysteresis in the PZT.

With the new driver we went from 0 to 100 V, adjusting the M16 axis by hand as well, but it did not have so much effect. (figure 2), RFC TRA was still between 3.0 and 3.1 V.

At the end we reconnected the lemo1 of M15_axis_x to its driver and the transmission remained around 3.1 V.

To go further on this, the idea would be to swap the RFC QD2 quadrant photodiode that it is not working correctly and then better investigate the problem :
- Add some features to the online PZT driving to deal with the hysteresis
- Act on the picomotors in common between PSTAB and RFC and see if RFC situation can be improved without deteriorating the PSTAB one.

Images attached to this comment