During the opening of the NI tower, vacuum team observed that the ZnSe viewports show patterns as visible in Fig. 1 and Fig. 2 (Fig. 1: diagnostic viewport, Fig. 2: PAM viewport). These patterns suggest a possible delamination of the optical coatings from the window surfaces. Part of the coating material has already been collected by the vacuum team and will be analyzed via Scanning Electron Microscopy (SEM).
By visual inspection performed by Antonio and the vacuum team, no cracks in the ZnSe substrate have been identified.
A preliminary inspection of the viewports at WE and NE has been carried out by the vacuum team. It is noted that, at the end towers, only one viewport per tower is present (unlike the input towers, where two viewports are installed). The viewports appear to be in acceptable condition from the outside, although visibility is limited. The pattern is instead clearly visible from the inner side of the tower.
A further inspection of the WI viewports will be performed by the vacuum team as soon as possible.