The initial goal of the shift was to compensate for NI CP cold lens with NI DASes, following the work just started yesterday evening (56602).

The NI DASes powers setted yesterday remain constant over the night and thermalized. As asked, Gianmatteo performed the cavities scan this morning (56604) and the results are reported in fig. 1 and are not so different from the one obtained yesterday evening, before switching NI DASes ON (56601, fig. 1).

During the daily meeting, we agree on going back to the original condition (NI DASes OFF) and check again the mismatch of the cavities.

At 14.33 UTC ITF was set to NI single bounce configuration. After checking the HWS DET illumination and starting an acquisition, at 14.45 UTC NI DASes flip mirrors were closed.

We check the cavities mismatch two times during the NI DASes cooling phase: the results of all today cavities scan is reported in the following table:

Once the NI DASes cooling phase was completed (around 17.30 UTC), I noticed that wavefronts from yesterday night showed a NI DAS IN and OUT induced curvature on the bottom left side of HWS DET image (fig. 2), that is in a different position with respect to last NI RH center measurement performed on July 15th (entry 56453, fig.3)

Before proceeding with NI CP cold lens compensation measurements, we agree on 

check the true alignment between NI RH and NI CO2 actuators, performing the NI RH and CH centering measurement with HWS DET (originally foreseen for this morning and then canceled because of other noisy activities programmed during maintenance).

So after realigning the cavities locking the arms (as suggested by Fiodor) and set the NI single bounce, at 17.46 UTC a new HWS DET acquisition started and at 17.56 UTC the NI RH were switched ON at 15 W (i.e. 23.6 V).

After around 1 hour and half, NI RH coordinates were pretty stable (fig. 4).

So at 19.30 UTC I switched OFF the NI RH and immediately after I switched ON the NI CH, at high power.

At 21.30 UTC the curvature of NI CH still did not appear clearly, unexpectedly: the reason should be further investigated in the next shifts. 

We decided to interrupt today’s measurement.

At the end of the shift, all the NI CO2 beams were blocked on the bench and the ITF was left locked on IR.