This afternoon we had several unclocks after the OMC slow shutter is open. These were systematically (3 times) triggered by a too large power on B1s. The safety is triggered when the B1s power exceeds 45mW (which means ~500mW on SDB1).

Figure 1 and 2 show the locks of the past two days. The power on B1s used to be around 25mW with peaks up to 30mW. This has changed today between 11:00 UTC and 16:00 UTC. Where the power increased to be around 35mW-40mW with peaks crossing the 45mW threshold causing an unlock. What is strange is that the B1p power has not changed, and remains around 450mW. There might already have been an increase between July 31 and Aug 1, this is much less clear, and apparent mostly on B1s camera total power.

Figure 3 and 4 show the B1s and B1p camera when the shutter is open and the OMC not locked yet. Figure 3 is this afternoon, and figure 4 this morning. This afternoon there seem to be an additional beam that is round but off center on B1s, on B1p the central spot looks brighter.

We made some test to exclude that this extra beam is due to squeezing. Martina will describe those more in a different entry.

We manage to lock with some luck, as the power got a few mW lower on B1s.