Virgo Logbook

AdV-COM (AdV commissioning (1st part) )

mwas - 19:51 Sunday 03 August 2025 (67424)

Restoring double cavity pole frequency and continued SR TX offset

After the test done on Thursday evening at the end of the commissionign shift https://logbook.virgo-gw.eu/virgo/?r=67410, having a DCP around 180Hz instead of around 160Hz, and with an SR TX offset of 0.015 has proven to be effective to reach a higher BNS range. ~180Hz DCP is the frequency as measured by Hrec that we had since the beginning of O4b until Jul 15 when it change due to the change in the in-loop DCP signal after the DARM notch filter change.

During the unlock following the earthquake this morning at ~6:00 UTC I have changed the ITF_LOCK.ini file to sr_ty_dcp_set = 190, which sets the DCP as measured by Hrec around 180Hz.

Given how slow the SR TX control is (response time of more than one hour), the automation of the SR TX offset could be done at the same time as the SR TY offset is done, and with the same ~5s ramp as is used for SR TY. This is very low risk for the lock acquistion, from December 2024 to June 2025 we had many saturation of B1 photodiodes that where kicking the SR alignment in TX by ~0.5 urad in a matters of seconds without any issues.

Images attached to this report

67424_1754243138_Screenshot from 2025-08-03 18-42-02.png

Comments to this report:

mwas - 12:04 Monday 04 August 2025 (67428)

Figure 1. This morning a few seconds after the SR TY misalignment started I have added an SR TX offset of 0.015 with a 1s ramp. This has worked without a problems and a few hours later the BNS range reached 55 Mpc. It takes a few hours for ASC SR TX to reach fluctuation that are centered around zero.

Images attached to this comment

67428_1754301732_Screenshot from 2025-08-04 10-57-50.png

mwas - 21:37 Tuesday 05 August 2025 (67442)

Figure 1. Today during the relock after the maintenance I have added in the ITF_LOCK automation that an SR TX offset is added at the same time as the SR TY offset when acquiring LN3. This has worked successufully, and added the offset that of 0.015 that has been working well for the past few days.

Figure 2. The BNS range this afternoon has not been as good as before the maintenance, it may be due to some drift in alignment that occurred during the maintenance, SR TX changed by ~7urad, and the drift control is slowly recovering that with the SR TX error signal not actually managing to arrive back to zero.

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