The TCS measurements started at 7.30 pm. During this shift we performed some further tests with different DAS settings.
A deep analysis of the data will follow.
We leave the ITF locked with the DAS ON.
The different tests done yesterday are summarized in the following table (see figure 1).
| Test | Start (UTC) | End (UTC) | Power IN (mW) | Power OUT (mW) |
| 1 | 18:51 | 20:32 | 150* | 300* |
| 2 | 20:41 | 22:06 | 100 WI - 175 NI | 200 WI - 350 NI |
| 3 | 22:13 | 22:34 | 200* | 400* |
| 4 | 22:53 | -- | 100 WI -175 NI | 200 WI - 350 NI |
* same power applied on West and North CP.
As shown in figure 2 the maximum gain has been reached during the test #2, with differential heating applied to West and North CP.
At first glance, this seems to favour the hypotesis of the presence of a dominant diverging lens in the West CP (in agreement with the behavior of the contrast defect during CH tests, but in disagreement with the behavior of the recycling gain). Till now no clear conclusion, to be better investigated.
In this configuration, the time behavior of the recycling gain does not show the overshoot due to annular heating.
In order to evaluate the DAS power upper limit to maximize the 56 MHz gain, in test #3 the power has been increased up to 200 mW and 400 mW. An overcompensantion has been observed. Thus we decided to leave the ITF with the settings of configuration #2.
Further analyses of the ITF signals are ongoing.
