Virgo Logbook

This morning we restarted 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

We decide to perform steps by moving one actuator each time. For each step, the stability of the lock acquisition procedure will be checked.
The LN2 has been reached at 08.50 UTC. We waited for the SR alignment and, at 09.13 UTC, the first step was done by increasing NI outer power on the pickoff 0.561W → 0.580W (+100 mW).

	STEP 1 completed at 9.13 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	3.3
N	on the pickoff	0.338	0.04	0.537

The main effect of this step was the sideband increase.

We decided to perform a further step by increasing the NI outer by +50 mW. Before this, at 10.09 UTC the ITF has been settled to LN3 to have a reference point. The effect at LN2 and the stability of the lock acquisition will be evaluated after the thermalization time.

At 10.37 UTC NI outer increase pickoff 0.580W → 0.592W (+65 mW). After the unlock due to the earthquake, we checked the CO2 powers on the pickoff. The injected powers are summarized in the table below:

	STEP 2 completed at 10.37 UTC	CH [W]	INNER DAS [W]	OUTER DAS [W]
W	on the ITF	0.042	0	1.52
W	on the pickoff	0.258	0	0.247
N	on the ITF	0.055	0.276	3.41
N	on the pickoff	0.338	0.045	0.555

The BNS range with SR aligned was ~ 36 Mpc.

The BNS range with SR misaligned touched 49 Mpc.

The effects of STEP 2 will be evaluated in the afternoon shift.

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