The afternoon shift started from the CO2 powers configuration left in the previous shift (entry 63219) and reported in the following table:

We tested the lock acquisition of this CO2 powers configuration and at 14:50 UTC LN2 was reached. After 40 minutes (at 15:31 UTC), the WI DAS OUT was increased by +50 mW (1.52 W → 1.57 W), but at 16:42 UTC, the ITF unlocked (see dedicated entry). In Figure 1, the main ITF signals of this lock are shown, no big impact has been observed.

From this moment, it was easy to lock the CITF, but the value of the sidebands was low, the 12 MHz did not even exceed 0.05 mW. To address this situation, the NI CH was increased in order to follow the increase of the NI DAS OUT made in the morning. Two steps were taken: the power of the NI CH was increased by 1 mW (0.055 W → 0.056 W) at 18:29 UTC and then by 2 mW (0.056 W → 0.058 W) at 20:27 UTC, but again, no good effect was observed, see Figure 2.

Given the unclear situation, we decided to return to the starting point of the afternoon (where the sidebands at CITF were good and we had reached LN2). Therefore, at 20.51 UTC we reverted the NI CH and the WI DAS OUT back to their values of the starting point (NI CH: 0.055 W and WI DAS OUT: 1.52 W). In this case, however, the situation doesn't seem to have changed much either.