As seen in the entry 56715, the goal of the activity was to measure the induced curvature of the NI CO2 actuators. The CH power has been chosen to mimic the YAG beam and the DAS ones are chosen to compensate for it. The nominal values, from OSCAR simulations, are reported in the following table:

The NI DASes were already switched on (IN @ 0.075 W and OUT @ 1.7 W) in order to compensate for the NI CP cold lens.

To have a better knowledge of the ITF initial status, it was locked @CITF for 20 minutes and then a matching scan was performed (see entry 56727).

At 16.57 UTC the ITF was put in NI Single Bounce and at 16.59 UTC a DET HWS acquisition was started.

At 17.09 UTC the NI CH was switched ON at 0.141 W. When the CH curvature reached the steady state, the NI DASes powers were changed up to 0.4 W for the inner ring and 4.1 W for the outer one.

The entire behavior of the curvature is shown in figure 1, it could seem that we are overcompensating with the NI DAS powers, but the CH curvature steady state, according to the calibration (see VIR-0017A-22), is half of the value that we expected @ 0.141 W. We have to investigate further.

At the end of the measurement, a new matching scan was performed (see entry 56727) and the ITF was locked @CITF for 10 minutes.

At 21.28 UTC the ITF was locked on IR and we left the CO2 TCS actuator’s powers in the following condition: