Here is the report of the preliminary analysis of the WI WFs collected on May 29th during the cooling phase (60362). As done in the past, we looked at the first WFs right after the unlock to search for possible PAs. The situation is well summarized in figure 1, that shows three WFs of the WI taken at three different dates: August 25th, 2022 - December 30th, 2022 - May 29th, 2023. In all cases, the black cross indicates approximately the mirror center, and the coordinates (in meters) of the maps are in the ITM reference frame.

Comparing the three data sets, we can confirm, with good confidence level, that PAs are back on the WI. Positions are very different with respect to the past and are further away from the mirror center, but a quantitative analysis must be done. We'll also assess the impact on the ITF behavior (CD, SBs recycling gain...).

The fact that these “PAs” come and go supports the hypothesis that they are dust/dirt particles on the mirror surface rather than conventional PAs (embedded beneath the coating).