Virgo Logbook

This morning we started to tune the DAS powers in order to improve the ITF WP @ 18W.

The initial CO2 power values are listed in the table below:

	Starting point	CH [W]	INNER DAS [W]	OUTER DAS [W]
W	on the ITF	0.042	0	1.55
W	on the pickoff	0.258	0	0.252
N	on the ITF	0.055	0.240	3.2
N	on the pickoff	0.338	0.04	0.52

The LN2 has been reached at 08.05 UTC. We waited for the SR alignment and, at 08.56 UTC, the first differential step has been done (the WI outer ring power has been decreased and the NI one has been increased).

STEP 1

	STEP 1 completed at 8.56 UTC	CH [W]	INNER DAS [W]	OUTER DAS [W]
W	on the ITF	0.042	0	1.47
W	on the pickoff	0.258	0	0.24
N	on the ITF	0.055	0.240	3.42
N	on the pickoff	0.338	0.04	0.56

The main effect of this step was the sideband increase.

Than, two other steps have been done in different times:

-09.45 UTC: NI outer increase pickoff 0.605 → 0.63 (+150 mW)
-10.21 UTC: WI outer increase pickoff 0.246 → 0.267 (+130 mW)

After these two steps, the injected powers are:

	STEP 2 completed at 10.21 UTC	CH [W]	INNER DAS [W]	OUTER DAS [W]
W	on the ITF	0.042	0	1.62
W	on the pickoff	0.258	0	0.26
N	on the ITF	0.055	0.240	3.55
N	on the pickoff	0.338	0.04	0.58

The BNS range with SR aligned was ~ 39 Mpc.

At 11.38 UTC, the ITF has been settled to LN3.

The BNS range with SR misaligned touched 52 Mpc.

The main ITF signals during the shift are summarized in fig.1.

Lock acquisition has to be tested in this new CO2 DAS WPs.