At 00.30 LT, Diana acquired a thermal image of the NI CO2 bench and we compared it with the previous one taken during the 19 August maintenance (see Fig. 1).

The  image of this evening shows a localized hot spot not present in the earlier image, suggesting a possible partial obstruction of the beam path leading to power loss. This is consistent with the fact that the beam sampler at the laser output (TCS_NI_CO2_PWRLAS) shows no variation, while other bench signals do (see Fig. 2).

The sudden power drop is not correlated with temperature changes. The nominal power injected into the ITF was recovered by rotating the waveplate, but the beam shape (and consequently the DAS) may be affected by the possible obstruction.

This issue could prevent the ITF lock.
An urgent inspection of the NI bench is recommended to check for any foreign object or obstruction.