The goal of the shift is to check the centering of the NI CH/DAS on the CP centre identified by the lens induced by the RH (see entry 56329).

We went on the NI CO2 bench to investigate the problem of Hot Mirror (HM) picomotors and we noticed that their cable wasn’t connected. As soon as it was reconnected, the picomotors worked properly.

After that, we gathered a series of pictures with the thermal camera to check the reciprocal centering between CH and DAS. That was to exclude that the miscentering of CH on the CP was due to a miscentering of the CH with respect to the DAS on the bench. The first picture (see figure 1) is taken at a distance of about 210 cm from the HM. A graphical analysis of the picture provides the coordinates of the centre of the outer DAS ring as (158,123)+-2 in pixels. The centre of the CH is obtained as (162,120)+-2. Based on the known value of the OUT DAS diameter on the CP (about 24 cm), 1 pixel in the picture is found to correspond to roughly  2 mm. Another picture is taken farther, at about 270 cm. In this case, a quantitative analysis cannot be performed since the ring is too large for the screen. In any case, a good centering can be observed by eye (see figure 2).

In the afternoon we proceeded with the CH alignment.

At 15.17 UTC I started a new HWS-DET acquisition and at 15.20 UTC NI CH was switched on @ 356 mW.

All the HWS steady state maps are shown in figure 3 and the steps made to align the CH and their results are summarised in the following table.

After the last step, the NI-CH is better centred on the NI-RH centre, the differences are Y=(0.78 +- 0.11) cm and X=(0.22 +- 0.13) cm.

At 17.16 UTC I stopped the HWS acquisition and I left the TCS powers condition of June 28th (see entry 56314):